elfobj.c

/**
 * Compiler implementation of the
 * $(LINK2 http://www.dlang.org, D programming language).
 *
 * Copyright:   Copyright (C) ?-1998 by Symantec
 *              Copyright (c) 2000-2017 by Digital Mars, All Rights Reserved
 * Authors:     $(LINK2 http://www.digitalmars.com, Walter Bright)
 * License:     $(LINK2 http://www.boost.org/LICENSE_1_0.txt, Boost License 1.0)
 * Source:      $(LINK2 https://github.com/dlang/dmd/blob/master/src/ddmd/backend/elfobj.c, backend/elfobj.c)
 */


/****
 * Output to ELF object files
 * http://www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html
 */

#if SCPP || MARS
#include        <stdio.h>
#include        <string.h>
#include        <stdlib.h>

#if __sun
#include        <alloca.h>
#endif

#include        "cc.h"
#include        "global.h"
#include        "code.h"
#include        "type.h"
#include        "melf.h"
#include        "outbuf.h"
#include        "filespec.h"
#include        "cv4.h"
#include        "cgcv.h"
#include        "dt.h"

#include        "aa.h"
#include        "tinfo.h"

#if ELFOBJ

#include        "dwarf.h"

#include        "aa.h"
#include        "tinfo.h"

#ifndef ELFOSABI
# if TARGET_LINUX
#  define ELFOSABI ELFOSABI_LINUX
# elif TARGET_FREEBSD
#  define ELFOSABI ELFOSABI_FREEBSD
# elif TARGET_SOLARIS
#  define ELFOSABI ELFOSABI_SYSV
# elif TARGET_OPENBSD
#  define ELFOSABI ELFOSABI_OPENBSD
# else
#  error "No ELF OS ABI defined.  Please fix"
# endif
#endif

//#define DEBSYM 0x7E

static Outbuffer *fobjbuf;

static char __file__[] = __FILE__;      // for tassert.h
#include        "tassert.h"

#define MATCH_SECTION 1

#define DEST_LEN (IDMAX + IDOHD + 1)
char *obj_mangle2(Symbol *s,char *dest, size_t *destlen);

#if MARS
// C++ name mangling is handled by front end
#define cpp_mangle(s) ((s)->Sident)
#endif

void addSegmentToComdat(segidx_t seg, segidx_t comdatseg);

/**
 * If set the compiler requires full druntime support of the new
 * section registration.
 */
#define REQUIRE_DSO_REGISTRY (DMDV2 && (TARGET_LINUX || TARGET_FREEBSD))

/******
 * FreeBSD uses ELF, but the linker crashes with Elf comdats with the following message:
 *  /usr/bin/ld: BFD 2.15 [FreeBSD] 2004-05-23 internal error, aborting at
 *  /usr/src/gnu/usr.bin/binutils/libbfd/../../../../contrib/binutils/bfd/elfcode.h
 *  line 213 in bfd_elf32_swap_symbol_out
 * For the time being, just stick with Linux.
 */

#define ELF_COMDAT      TARGET_LINUX

/***************************************************
 * Correspondence of relocation types
 *      386             32 bit in 64      64 in 64
 *      R_386_32        R_X86_64_32       R_X86_64_64
 *      R_386_GOTOFF    R_X86_64_PC32     R_X86_64_
 *      R_386_GOTPC     R_X86_64_         R_X86_64_
 *      R_386_GOT32     R_X86_64_         R_X86_64_
 *      R_386_TLS_GD    R_X86_64_TLSGD    R_X86_64_
 *      R_386_TLS_IE    R_X86_64_GOTTPOFF R_X86_64_
 *      R_386_TLS_LE    R_X86_64_TPOFF32  R_X86_64_
 *      R_386_PLT32     R_X86_64_PLT32    R_X86_64_
 *      R_386_PC32      R_X86_64_PC32     R_X86_64_
 */

/******************************************
 */

symbol *GOTsym; // global offset table reference

symbol *Obj::getGOTsym()
{
    if (!GOTsym)
    {
        GOTsym = symbol_name("_GLOBAL_OFFSET_TABLE_",SCglobal,tspvoid);
    }
    return GOTsym;
}

void Obj::refGOTsym()
{
    if (!GOTsym)
    {
        symbol *s = Obj::getGOTsym();
        Obj::external(s);
    }
}

static void objfile_write(FILE *fd, void *buffer, unsigned len);

STATIC char * objmodtoseg (const char *modname);
STATIC void objfixupp (struct FIXUP *);
STATIC void ledata_new (int seg,targ_size_t offset);
STATIC void obj_tlssections();
#if MARS
static void obj_rtinit();
#endif
static void addSectionToComdat(IDXSEC secidx, segidx_t comdatseg);

static IDXSYM elf_addsym(IDXSTR sym, targ_size_t val, unsigned sz,
                         unsigned typ,unsigned bind,IDXSEC sec,
                         unsigned char visibility=STV_DEFAULT);
static long elf_align(targ_size_t size, long offset);

// The object file is built is several separate pieces

// Non-repeatable section types have single output buffers
//      Pre-allocated buffers are defined for:
//              Section Names string table
//              Section Headers table
//              Symbol table
//              String table
//              Notes section
//              Comment data

// Section Names  - String table for section names only
static Outbuffer *section_names;
#define SEC_NAMES_INIT  800
#define SEC_NAMES_INC   400

// Hash table for section_names
AArray *section_names_hashtable;

int jmpseg;

/* ====================== Cached Strings in section_names ================= */

struct TypeInfo_Idxstr : TypeInfo
{
    const char* toString();
    hash_t getHash(void *p);
    int equals(void *p1, void *p2);
    int compare(void *p1, void *p2);
    size_t tsize();
    void swap(void *p1, void *p2);
};

TypeInfo_Idxstr ti_idxstr;

const char* TypeInfo_Idxstr::toString()
{
    return "IDXSTR";
}

hash_t TypeInfo_Idxstr::getHash(void *p)
{
    IDXSTR a = *(IDXSTR *)p;
    hash_t hash = 0;
    for (const char *s = (char *)(section_names->buf + a);
         *s;
         s++)
    {
        hash = hash * 11 + *s;
    }
    return hash;
}

int TypeInfo_Idxstr::equals(void *p1, void *p2)
{
    IDXSTR a1 = *(IDXSTR*)p1;
    IDXSTR a2 = *(IDXSTR*)p2;
    const char *s1 = (char *)(section_names->buf + a1);
    const char *s2 = (char *)(section_names->buf + a2);

    return strcmp(s1, s2) == 0;
}

int TypeInfo_Idxstr::compare(void *p1, void *p2)
{
    IDXSTR a1 = *(IDXSTR*)p1;
    IDXSTR a2 = *(IDXSTR*)p2;
    const char *s1 = (char *)(section_names->buf + a1);
    const char *s2 = (char *)(section_names->buf + a2);

    return strcmp(s1, s2);
}

size_t TypeInfo_Idxstr::tsize()
{
    return sizeof(IDXSTR);
}

void TypeInfo_Idxstr::swap(void *p1, void *p2)
{
    assert(0);
}


/* ======================================================================== */

// String Table  - String table for all other names
static Outbuffer *symtab_strings;


// Section Headers
Outbuffer  *SECbuf;             // Buffer to build section table in
#define SecHdrTab ((Elf32_Shdr *)SECbuf->buf)
#define GET_SECTION(secidx) (SecHdrTab + secidx)
#define GET_SECTION_NAME(secidx) (section_names->buf + SecHdrTab[secidx].sh_name)

// The relocation for text and data seems to get lost.
// Try matching the order gcc output them
// This means defining the sections and then removing them if they are
// not used.
static int section_cnt; // Number of sections in table

#define SHN_TEXT        1
#define SHN_RELTEXT     2
#define SHN_DATA        3
#define SHN_RELDATA     4
#define SHN_BSS         5
#define SHN_RODAT       6
#define SHN_STRINGS     7
#define SHN_SYMTAB      8
#define SHN_SECNAMES    9
#define SHN_COM         10
#define SHN_NOTE        11
#define SHN_GNUSTACK    12
#define SHN_CDATAREL    13

IDXSYM *mapsec2sym;
#define S2S_INC 20

#define SymbolTable   ((Elf32_Sym *)SYMbuf->buf)
#define SymbolTable64 ((Elf64_Sym *)SYMbuf->buf)
static int symbol_idx;          // Number of symbols in symbol table
static int local_cnt;           // Number of symbols with STB_LOCAL

#define STI_FILE 1              // Where file symbol table entry is
#define STI_TEXT 2
#define STI_DATA 3
#define STI_BSS  4
#define STI_GCC  5              // Where "gcc2_compiled" symbol is */
#define STI_RODAT 6             // Symbol for readonly data
#define STI_NOTE 7              // Where note symbol table entry is
#define STI_COM  8
#define STI_CDATAREL 9          // Symbol for readonly data with relocations

// NOTE: There seems to be a requirement that the read-only data have the
// same symbol table index and section index. Use section NOTE as a place
// holder. When a read-only string section is required, swap to NOTE.

// Symbol Table
Outbuffer  *SYMbuf;             // Buffer to build symbol table in
static Outbuffer *reset_symbuf; // Keep pointers to reset symbols

// Extended section header indices
static Outbuffer *shndx_data;
static const IDXSEC secidx_shndx = SHN_HIRESERVE + 1;

// Notes data (note currently used)
static Outbuffer *note_data;
static IDXSEC secidx_note;      // Final table index for note data

// Comment data for compiler version
static Outbuffer *comment_data;
static const char compiler[] = "\0Digital Mars C/C++"
        VERSION
        ;       // compiled by ...

// Each compiler segment is an elf section
// Predefined compiler segments CODE,DATA,CDATA,UDATA map to indexes
//      into SegData[]
//      An additionl index is reserved for comment data
//      New compiler segments are added to end.
//
// There doesn't seem to be any way to get reserved data space in the
//      same section as initialized data or code, so section offsets should
//      be continuous when adding data. Fix-ups anywhere withing existing data.

#define COMD CDATAREL+1
#define OB_SEG_SIZ      10              // initial number of segments supported
#define OB_SEG_INC      10              // increment for additional segments

#define OB_CODE_STR     100000          // initial size for code
#define OB_CODE_INC     100000          // increment for additional code
#define OB_DATA_STR     100000          // initial size for data
#define OB_DATA_INC     100000          // increment for additional data
#define OB_CDATA_STR      1024          // initial size for data
#define OB_CDATA_INC      1024          // increment for additional data
#define OB_COMD_STR        256          // initial size for comments
                                        // increment as needed
#define OB_XTRA_STR        250          // initial size for extra segments
#define OB_XTRA_INC      10000          // increment size

#define MAP_SEG2SECIDX(seg) (SegData[seg]->SDshtidx)
#define MAP_SEG2SYMIDX(seg) (SegData[seg]->SDsymidx)
#define MAP_SEG2SEC(seg) (&SecHdrTab[MAP_SEG2SECIDX(seg)])
#define MAP_SEG2TYP(seg) (MAP_SEG2SEC(seg)->sh_flags & SHF_EXECINSTR ? CODE : DATA)

seg_data **SegData;
int seg_count;
int seg_max;
int seg_tlsseg = UNKNOWN;
int seg_tlsseg_bss = UNKNOWN;

static int elf_addsegment2(IDXSEC shtidx, IDXSYM symidx, IDXSEC relidx);
static int elf_addsegment(IDXSTR namidx, int type, int flags, int align);
static int elf_getsegment(IDXSTR namidx);

/*******************************
 * Output a string into a string table
 * Input:
 *      strtab  =       string table for entry
 *      str     =       string to add
 *
 * Returns index into the specified string table.
 */

IDXSTR Obj::addstr(Outbuffer *strtab, const char *str)
{
    //dbg_printf("Obj::addstr(strtab = x%x str = '%s')\n",strtab,str);
    IDXSTR idx = strtab->size();        // remember starting offset
    strtab->writeString(str);
    //dbg_printf("\tidx %d, new size %d\n",idx,strtab->size());
    return idx;
}

/*******************************
 * Find a string in a string table
 * Input:
 *      strtab  =       string table for entry
 *      str     =       string to find
 *
 * Returns index into the specified string table or 0.
 */

static IDXSTR elf_findstr(Outbuffer *strtab, const char *str, const char *suffix)
{
    //printf("elf_findstr(strtab = %p, str = %s, suffix = %s\n", strtab, str ? str : "", suffix ? suffix : "");

    size_t len = strlen(str);

    // Combine str~suffix and have buf point to the combination
#ifdef DEBUG
    char tmpbuf[25];    // to exercise the alloca() code path
#else
    char tmpbuf[1024];  // the alloca() code path is slow
#endif
    const char *buf;
    if (suffix)
    {
        size_t suffixlen = strlen(suffix);
        if (len + suffixlen >= sizeof(tmpbuf))
        {
             buf = (char *)alloca(len + suffixlen + 1);
             assert(buf);
        }
        else
        {
             buf = tmpbuf;
        }
        memcpy((char *)buf, str, len);
        memcpy((char *)buf + len, suffix, suffixlen + 1);
        len += suffixlen;
    }
    else
        buf = str;

    // Linear search, slow
    const char *ent = (char *)strtab->buf+1;
    const char *pend = ent+strtab->size() - 1;
    while (ent + len < pend)
    {
        if (memcmp(buf, ent, len + 1) == 0)
            return ent - (const char *)strtab->buf;
        ent = (const char *)memchr(ent, 0, pend - ent);
        ent += 1;
    }
    return 0;                   // never found match
}

/*******************************
 * Output a mangled string into the symbol string table
 * Input:
 *      str     =       string to add
 *
 * Returns index into the table.
 */

static IDXSTR elf_addmangled(Symbol *s)
{
    //printf("elf_addmangled(%s)\n", s->Sident);
    char dest[DEST_LEN];

    IDXSTR namidx = symtab_strings->size();
    size_t len;
    char *destr = obj_mangle2(s, dest, &len);
    const char *name = destr;
    if (CPP && name[0] == '_' && name[1] == '_')
    {
        if (strncmp(name,"__ct__",6) == 0)
        {
            name += 4;
            len -= 4;
        }
#if 0
        switch(name[2])
        {
            case 'c':
                if (strncmp(name,"__ct__",6) == 0)
                    name += 4;
                break;
            case 'd':
                if (strcmp(name,"__dl__FvP") == 0)
                    name = "__builtin_delete";
                break;
            case 'v':
                //if (strcmp(name,"__vec_delete__FvPiUIPi") == 0)
                    //name = "__builtin_vec_del";
                //else
                //if (strcmp(name,"__vn__FPUI") == 0)
                    //name = "__builtin_vec_new";
                break;
            case 'n':
                if (strcmp(name,"__nw__FPUI") == 0)
                    name = "__builtin_new";
                break;
        }
#endif
    }
    else if (tyfunc(s->ty()) && s->Sfunc && s->Sfunc->Fredirect)
    {
        name = s->Sfunc->Fredirect;
        len = strlen(name);
    }
    symtab_strings->reserve(len+1);
    memcpy((char *)symtab_strings->p, name, len + 1);
    symtab_strings->setsize(namidx+len+1);
    if (destr != dest)                  // if we resized result
        mem_free(destr);
    //dbg_printf("\telf_addmagled symtab_strings %s namidx %d len %d size %d\n",name, namidx,len,symtab_strings->size());
    return namidx;
}

/*******************************
 * Output a symbol into the symbol table
 * Input:
 *      stridx  =       string table index for name
 *      val     =       value associated with symbol
 *      sz      =       symbol size
 *      typ     =       symbol type
 *      bind    =       symbol binding
 *      sec     =       index of section where symbol is defined
 *      visibility  =   visibility of symbol (STV_xxxx)
 *
 * Returns the symbol table index for the symbol
 */

static IDXSYM elf_addsym(IDXSTR nam, targ_size_t val, unsigned sz,
                         unsigned typ, unsigned bind, IDXSEC sec,
                         unsigned char visibility /*= STV_DEFAULT*/)
{
    //dbg_printf("elf_addsym(nam %d, val %d, sz %x, typ %x, bind %x, sec %d\n",
            //nam,val,sz,typ,bind,sec);

    /* We want globally defined data symbols to have a size because
     * zero sized symbols break copy relocations for shared libraries.
     */
    if(sz == 0 && (bind == STB_GLOBAL || bind == STB_WEAK) &&
       (typ == STT_OBJECT || typ == STT_TLS) &&
       sec != SHN_UNDEF)
       sz = 1; // so fake it if it doesn't

    if (sec > SHN_HIRESERVE)
    {   // If the section index is too big we need to store it as
        // extended section header index.
        if (!shndx_data)
            shndx_data = new Outbuffer(50 * sizeof(Elf64_Word));
        // fill with zeros up to symbol_idx
        const size_t shndx_idx = shndx_data->size() / sizeof(Elf64_Word);
        shndx_data->writezeros((symbol_idx - shndx_idx) * sizeof(Elf64_Word));

        shndx_data->write32(sec);
        sec = SHN_XINDEX;
    }

    if (I64)
    {
        if (!SYMbuf)
        {   SYMbuf = new Outbuffer(50 * sizeof(Elf64_Sym));
            SYMbuf->reserve(100 * sizeof(Elf64_Sym));
        }
        Elf64_Sym sym;
        sym.st_name = nam;
        sym.st_value = val;
        sym.st_size = sz;
        sym.st_info = ELF64_ST_INFO(bind,typ);
        sym.st_other = visibility;
        sym.st_shndx = sec;
        SYMbuf->write(&sym,sizeof(sym));
    }
    else
    {
        if (!SYMbuf)
        {   SYMbuf = new Outbuffer(50 * sizeof(Elf32_Sym));
            SYMbuf->reserve(100 * sizeof(Elf32_Sym));
        }
        Elf32_Sym sym;
        sym.st_name = nam;
        sym.st_value = val;
        sym.st_size = sz;
        sym.st_info = ELF32_ST_INFO(bind,typ);
        sym.st_other = visibility;
        sym.st_shndx = sec;
        SYMbuf->write(&sym,sizeof(sym));
    }
    if (bind == STB_LOCAL)
        local_cnt++;
    //dbg_printf("\treturning symbol table index %d\n",symbol_idx);
    return symbol_idx++;
}

/*******************************
 * Create a new section header table entry.
 *
 * Input:
 *      name    =       section name
 *      suffix  =       suffix for name or NULL
 *      type    =       type of data in section sh_type
 *      flags   =       attribute flags sh_flags
 * Output:
 *      section_cnt = assigned number for this section
 *              Note: Sections will be reordered on output
 */

static IDXSEC elf_newsection2(
        Elf32_Word name,
        Elf32_Word type,
        Elf32_Word flags,
        Elf32_Addr addr,
        Elf32_Off offset,
        Elf32_Word size,
        Elf32_Word link,
        Elf32_Word info,
        Elf32_Word addralign,
        Elf32_Word entsize)
{
    Elf32_Shdr sec;

    sec.sh_name = name;
    sec.sh_type = type;
    sec.sh_flags = flags;
    sec.sh_addr = addr;
    sec.sh_offset = offset;
    sec.sh_size = size;
    sec.sh_link = link;
    sec.sh_info = info;
    sec.sh_addralign = addralign;
    sec.sh_entsize = entsize;

    if (!SECbuf)
    {   SECbuf = new Outbuffer(4 * sizeof(Elf32_Shdr));
        SECbuf->reserve(16 * sizeof(Elf32_Shdr));
    }
    if (section_cnt == SHN_LORESERVE)
    {   // insert dummy null sections to skip reserved section indices
        section_cnt = SHN_HIRESERVE + 1;
        SECbuf->writezeros((SHN_HIRESERVE + 1 - SHN_LORESERVE) * sizeof(sec));
        // shndx itself becomes the first section with an extended index
        IDXSTR namidx = Obj::addstr(section_names, ".symtab_shndx");
        elf_newsection2(namidx,SHT_SYMTAB_SHNDX,0,0,0,0,SHN_SYMTAB,0,4,4);
    }
    SECbuf->write((void *)&sec, sizeof(sec));
    return section_cnt++;
}

/**
Add a new section name or get the string table index of an existing entry.

Params:
    name = name of section
    suffix = append to name
    padded = set to true when entry was newly added
Returns:
    String index of new or existing section name.
 */
static IDXSTR elf_addsectionname(const char *name, const char *suffix = NULL, bool *padded = NULL)
{
    IDXSTR namidx = section_names->size();
    section_names->writeString(name);
    if (suffix)
    {   // Append suffix string
        section_names->setsize(section_names->size() - 1);  // back up over terminating 0
        section_names->writeString(suffix);
    }
    IDXSTR *pidx = (IDXSTR *)section_names_hashtable->get(&namidx);
    if (*pidx)
    {
        // this section name already exists, remove addition
        section_names->setsize(namidx);
        return *pidx;
    }
    if (padded)
        *padded = true;
    return *pidx = namidx;
}

static IDXSEC elf_newsection(const char *name, const char *suffix,
        Elf32_Word type, Elf32_Word flags)
{
    // dbg_printf("elf_newsection(%s,%s,type %d, flags x%x)\n",
    //        name?name:"",suffix?suffix:"",type,flags);
    bool added = false;
    IDXSTR namidx = elf_addsectionname(name, suffix, &added);
    assert(added);

    return elf_newsection2(namidx,type,flags,0,0,0,0,0,0,0);
}

/**************************
 * Ouput read only data and generate a symbol for it.
 *
 */

symbol *Obj::sym_cdata(tym_t ty,char *p,int len)
{
    symbol *s;

#if 0
    if (OPT_IS_SET(OPTfwritable_strings))
    {
        alignOffset(DATA, tysize(ty));
        s = symboldata(Offset(DATA), ty);
        SegData[DATA]->SDbuf->write(p,len);
        s->Sseg = DATA;
        s->Soffset = Offset(DATA);   // Remember its offset into DATA section
        Offset(DATA) += len;
    }
    else
#endif
    {
        //printf("Obj::sym_cdata(ty = %x, p = %x, len = %d, Offset(CDATA) = %x)\n", ty, p, len, Offset(CDATA));
        alignOffset(CDATA, tysize(ty));
        s = symboldata(Offset(CDATA), ty);
        Obj::bytes(CDATA, Offset(CDATA), len, p);
        s->Sseg = CDATA;
    }

    s->Sfl = /*(config.flags3 & CFG3pic) ? FLgotoff :*/ FLextern;
    return s;
}

/**************************
 * Ouput read only data for data.
 * Output:
 *      *pseg   segment of that data
 * Returns:
 *      offset of that data
 */

int Obj::data_readonly(char *p, int len, int *pseg)
{
    int oldoff = Offset(CDATA);
    SegData[CDATA]->SDbuf->reserve(len);
    SegData[CDATA]->SDbuf->writen(p,len);
    Offset(CDATA) += len;
    *pseg = CDATA;
    return oldoff;
}

int Obj::data_readonly(char *p, int len)
{
    int pseg;

    return Obj::data_readonly(p, len, &pseg);
}

/******************************
 * Get segment for readonly string literals.
 * The linker will pool strings in this section.
 * Params:
 *    sz = number of bytes per character (1, 2, or 4)
 * Returns:
 *    segment index
 */
int Obj::string_literal_segment(unsigned sz)
{
    /* Elf special sections:
     * .rodata.strM.N - M is size of character
     *                  N is alignment
     * .rodata.cstN   - N fixed size readonly constants N bytes in size,
     *              aligned to the same size
     */
    static const char name[3][4] = { "1.1", "2.2", "4.4" };
    const int i = (sz == 4) ? 2 : sz - 1;
    const IDXSEC seg =
        ElfObj::getsegment(".rodata.str", name[i], SHT_PROGBITS, SHF_ALLOC | SHF_MERGE | SHF_STRINGS, sz);
    return seg;
}

/******************************
 * Perform initialization that applies to all .o output files.
 *      Called before any other obj_xxx routines
 */

Obj *Obj::init(Outbuffer *objbuf, const char *filename, const char *csegname)
{
    //printf("Obj::init()\n");
    ElfObj *obj = new ElfObj();

    cseg = CODE;
    fobjbuf = objbuf;

    mapsec2sym = NULL;
    note_data = NULL;
    secidx_note = 0;
    comment_data = NULL;
    seg_tlsseg = UNKNOWN;
    seg_tlsseg_bss = UNKNOWN;
    GOTsym = NULL;

    // Initialize buffers

    if (symtab_strings)
        symtab_strings->setsize(1);
    else
    {   symtab_strings = new Outbuffer(1024);
        symtab_strings->reserve(2048);
        symtab_strings->writeByte(0);
    }

    if (SECbuf)
        SECbuf->setsize(0);
    section_cnt = 0;

    if (I64)
    {
        static char section_names_init64[] =
          "\0.symtab\0.strtab\0.shstrtab\0.text\0.data\0.bss\0.note\0.comment\0.rodata\0.note.GNU-stack\0.data.rel.ro\0.rela.text\0.rela.data";
        #define NAMIDX_NONE      0
        #define NAMIDX_SYMTAB    1       // .symtab
        #define NAMIDX_STRTAB    9       // .strtab
        #define NAMIDX_SHSTRTAB 17      // .shstrtab
        #define NAMIDX_TEXT     27      // .text
        #define NAMIDX_DATA     33      // .data
        #define NAMIDX_BSS      39      // .bss
        #define NAMIDX_NOTE     44      // .note
        #define NAMIDX_COMMENT  50      // .comment
        #define NAMIDX_RODATA   59      // .rodata
        #define NAMIDX_GNUSTACK 67      // .note.GNU-stack
        #define NAMIDX_CDATAREL 83      // .data.rel.ro
        #define NAMIDX_RELTEXT  96      // .rel.text and .rela.text
        #define NAMIDX_RELDATA  106     // .rel.data
        #define NAMIDX_RELDATA64 107    // .rela.data

        if (section_names)
            section_names->setsize(sizeof(section_names_init64));
        else
        {   section_names = new Outbuffer(512);
            section_names->reserve(1024);
            section_names->writen(section_names_init64, sizeof(section_names_init64));
        }

        if (section_names_hashtable)
            delete section_names_hashtable;
        section_names_hashtable = new AArray(&ti_idxstr, sizeof(IDXSTR));

        // name,type,flags,addr,offset,size,link,info,addralign,entsize
        elf_newsection2(0,               SHT_NULL,   0,                 0,0,0,0,0, 0,0);
        elf_newsection2(NAMIDX_TEXT,SHT_PROGBITS,SHF_ALLOC|SHF_EXECINSTR,0,0,0,0,0, 4,0);
        elf_newsection2(NAMIDX_RELTEXT,SHT_RELA, 0,0,0,0,SHN_SYMTAB,     SHN_TEXT, 8,0x18);
        elf_newsection2(NAMIDX_DATA,SHT_PROGBITS,SHF_ALLOC|SHF_WRITE,   0,0,0,0,0, 8,0);
        elf_newsection2(NAMIDX_RELDATA64,SHT_RELA, 0,0,0,0,SHN_SYMTAB,   SHN_DATA, 8,0x18);
        elf_newsection2(NAMIDX_BSS, SHT_NOBITS,SHF_ALLOC|SHF_WRITE,     0,0,0,0,0, 16,0);
        elf_newsection2(NAMIDX_RODATA,SHT_PROGBITS,SHF_ALLOC,           0,0,0,0,0, 16,0);
        elf_newsection2(NAMIDX_STRTAB,SHT_STRTAB, 0,                    0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_SYMTAB,SHT_SYMTAB, 0,                    0,0,0,0,0, 8,0);
        elf_newsection2(NAMIDX_SHSTRTAB,SHT_STRTAB, 0,                  0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_COMMENT, SHT_PROGBITS,0,                 0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_NOTE,SHT_NOTE,   0,                      0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_GNUSTACK,SHT_PROGBITS,0,                 0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_CDATAREL,SHT_PROGBITS,SHF_ALLOC|SHF_WRITE,0,0,0,0,0, 16,0);

        IDXSTR namidx;
        namidx = NAMIDX_TEXT;      *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_RELTEXT;   *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_DATA;      *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_RELDATA64; *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_BSS;       *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_RODATA;    *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_STRTAB;    *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_SYMTAB;    *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_SHSTRTAB;  *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_COMMENT;   *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_NOTE;      *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_GNUSTACK;  *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_CDATAREL;  *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
    }
    else
    {
        static char section_names_init[] =
          "\0.symtab\0.strtab\0.shstrtab\0.text\0.data\0.bss\0.note\0.comment\0.rodata\0.note.GNU-stack\0.data.rel.ro\0.rel.text\0.rel.data";

        if (section_names)
            section_names->setsize(sizeof(section_names_init));
        else
        {   section_names = new Outbuffer(512);
            section_names->reserve(100*1024);
            section_names->writen(section_names_init, sizeof(section_names_init));
        }

        if (section_names_hashtable)
            delete section_names_hashtable;
        section_names_hashtable = new AArray(&ti_idxstr, sizeof(IDXSTR));

        // name,type,flags,addr,offset,size,link,info,addralign,entsize
        elf_newsection2(0,               SHT_NULL,   0,                 0,0,0,0,0, 0,0);
        elf_newsection2(NAMIDX_TEXT,SHT_PROGBITS,SHF_ALLOC|SHF_EXECINSTR,0,0,0,0,0, 16,0);
        elf_newsection2(NAMIDX_RELTEXT,SHT_REL, 0,0,0,0,SHN_SYMTAB,      SHN_TEXT, 4,8);
        elf_newsection2(NAMIDX_DATA,SHT_PROGBITS,SHF_ALLOC|SHF_WRITE,   0,0,0,0,0, 4,0);
        elf_newsection2(NAMIDX_RELDATA,SHT_REL, 0,0,0,0,SHN_SYMTAB,      SHN_DATA, 4,8);
        elf_newsection2(NAMIDX_BSS, SHT_NOBITS,SHF_ALLOC|SHF_WRITE,     0,0,0,0,0, 32,0);
        elf_newsection2(NAMIDX_RODATA,SHT_PROGBITS,SHF_ALLOC,           0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_STRTAB,SHT_STRTAB, 0,                    0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_SYMTAB,SHT_SYMTAB, 0,                    0,0,0,0,0, 4,0);
        elf_newsection2(NAMIDX_SHSTRTAB,SHT_STRTAB, 0,                  0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_COMMENT, SHT_PROGBITS,0,                 0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_NOTE,SHT_NOTE,   0,                      0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_GNUSTACK,SHT_PROGBITS,0,                 0,0,0,0,0, 1,0);
        elf_newsection2(NAMIDX_CDATAREL,SHT_PROGBITS,SHF_ALLOC|SHF_WRITE,0,0,0,0,0, 1,0);

        IDXSTR namidx;
        namidx = NAMIDX_TEXT;      *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_RELTEXT;   *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_DATA;      *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_RELDATA;   *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_BSS;       *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_RODATA;    *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_STRTAB;    *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_SYMTAB;    *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_SHSTRTAB;  *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_COMMENT;   *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_NOTE;      *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_GNUSTACK;  *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
        namidx = NAMIDX_CDATAREL;  *(IDXSTR *)section_names_hashtable->get(&namidx) = namidx;
    }

    if (SYMbuf)
        SYMbuf->setsize(0);
    if (reset_symbuf)
    {
        symbol **p = (symbol **)reset_symbuf->buf;
        const size_t n = reset_symbuf->size() / sizeof(symbol *);
        for (size_t i = 0; i < n; ++i)
            symbol_reset(p[i]);
        reset_symbuf->setsize(0);
    }
    else
    {
        reset_symbuf = new Outbuffer(50 * sizeof(symbol *));
    }
    if (shndx_data)
        shndx_data->setsize(0);
    symbol_idx = 0;
    local_cnt = 0;
    // The symbols that every object file has
    elf_addsym(0, 0, 0, STT_NOTYPE,  STB_LOCAL, 0);
    elf_addsym(0, 0, 0, STT_FILE,    STB_LOCAL, SHN_ABS);       // STI_FILE
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_TEXT);      // STI_TEXT
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_DATA);      // STI_DATA
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_BSS);       // STI_BSS
    elf_addsym(0, 0, 0, STT_NOTYPE,  STB_LOCAL, SHN_TEXT);      // STI_GCC
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_RODAT);     // STI_RODAT
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_NOTE);      // STI_NOTE
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_COM);       // STI_COM
    elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, SHN_CDATAREL);  // STI_CDATAREL

    // Initialize output buffers for CODE, DATA and COMMENTS
    //      (NOTE not supported, BSS not required)

    seg_count = 0;

    elf_addsegment2(SHN_TEXT, STI_TEXT, SHN_RELTEXT);
    assert(SegData[CODE]->SDseg == CODE);

    elf_addsegment2(SHN_DATA, STI_DATA, SHN_RELDATA);
    assert(SegData[DATA]->SDseg == DATA);

    elf_addsegment2(SHN_RODAT, STI_RODAT, 0);
    assert(SegData[CDATA]->SDseg == CDATA);

    elf_addsegment2(SHN_BSS, STI_BSS, 0);
    assert(SegData[UDATA]->SDseg == UDATA);

    elf_addsegment2(SHN_CDATAREL, STI_CDATAREL, 0);
    assert(SegData[CDATAREL]->SDseg == CDATAREL);

    elf_addsegment2(SHN_COM, STI_COM, 0);
    assert(SegData[COMD]->SDseg == COMD);

    dwarf_initfile(filename);
    return obj;
}

/**************************
 * Initialize the start of object output for this particular .o file.
 *
 * Input:
 *      filename:       Name of source file
 *      csegname:       User specified default code segment name
 */

void Obj::initfile(const char *filename, const char *csegname, const char *modname)
{
    //dbg_printf("Obj::initfile(filename = %s, modname = %s)\n",filename,modname);

    IDXSTR name = Obj::addstr(symtab_strings, filename);
    if (I64)
        SymbolTable64[STI_FILE].st_name = name;
    else
        SymbolTable[STI_FILE].st_name = name;

#if 0
    // compiler flag for linker
    if (I64)
        SymbolTable64[STI_GCC].st_name = Obj::addstr(symtab_strings,"gcc2_compiled.");
    else
        SymbolTable[STI_GCC].st_name = Obj::addstr(symtab_strings,"gcc2_compiled.");
#endif

    if (csegname && *csegname && strcmp(csegname,".text"))
    {   // Define new section and make it the default for cseg segment
        // NOTE: cseg is initialized to CODE
        IDXSEC newsecidx;
        Elf32_Shdr *newtextsec;
        IDXSYM newsymidx;
        SegData[cseg]->SDshtidx = newsecidx =
            elf_newsection(csegname,0,SHT_PROGBITS,SHF_ALLOC|SHF_EXECINSTR);
        newtextsec = &SecHdrTab[newsecidx];
        newtextsec->sh_addralign = 4;
        SegData[cseg]->SDsymidx =
            elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, newsecidx);
    }
    if (config.fulltypes)
        dwarf_initmodule(filename, modname);
}

/***************************
 * Renumber symbols so they are
 * ordered as locals, weak and then global
 * Returns:
 *      sorted symbol table, caller must free with util_free()
 */

void *elf_renumbersyms()
{   void *symtab;
    int nextlocal = 0;
    int nextglobal = local_cnt;

    SYMIDX *sym_map = (SYMIDX *)util_malloc(sizeof(SYMIDX),symbol_idx);

    if (I64)
    {
        Elf64_Sym *oldsymtab = (Elf64_Sym *)SYMbuf->buf;
        Elf64_Sym *symtabend = oldsymtab+symbol_idx;

        symtab = util_malloc(sizeof(Elf64_Sym),symbol_idx);

        Elf64_Sym *sl = (Elf64_Sym *)symtab;
        Elf64_Sym *sg = sl + local_cnt;

        int old_idx = 0;
        for(Elf64_Sym *s = oldsymtab; s != symtabend; s++)
        {   // reorder symbol and map new #s to old
            int bind = ELF64_ST_BIND(s->st_info);
            if (bind == STB_LOCAL)
            {
                *sl++ = *s;
                sym_map[old_idx] = nextlocal++;
            }
            else
            {
                *sg++ = *s;
                sym_map[old_idx] = nextglobal++;
            }
            old_idx++;
        }
    }
    else
    {
        Elf32_Sym *oldsymtab = (Elf32_Sym *)SYMbuf->buf;
        Elf32_Sym *symtabend = oldsymtab+symbol_idx;

        symtab = util_malloc(sizeof(Elf32_Sym),symbol_idx);

        Elf32_Sym *sl = (Elf32_Sym *)symtab;
        Elf32_Sym *sg = sl + local_cnt;

        int old_idx = 0;
        for(Elf32_Sym *s = oldsymtab; s != symtabend; s++)
        {   // reorder symbol and map new #s to old
            int bind = ELF32_ST_BIND(s->st_info);
            if (bind == STB_LOCAL)
            {
                *sl++ = *s;
                sym_map[old_idx] = nextlocal++;
            }
            else
            {
                *sg++ = *s;
                sym_map[old_idx] = nextglobal++;
            }
            old_idx++;
        }
    }

    // Reorder extended section header indices
    if (shndx_data && shndx_data->size())
    {
        // fill with zeros up to symbol_idx
        const size_t shndx_idx = shndx_data->size() / sizeof(Elf64_Word);
        shndx_data->writezeros((symbol_idx - shndx_idx) * sizeof(Elf64_Word));

        Elf64_Word *old_buf = (Elf64_Word *)shndx_data->buf;
        Elf64_Word *tmp_buf = (Elf64_Word *)util_malloc(sizeof(Elf64_Word), symbol_idx);
        for (SYMIDX old_idx = 0; old_idx < symbol_idx; ++old_idx)
        {
            const SYMIDX new_idx = sym_map[old_idx];
            tmp_buf[new_idx] = old_buf[old_idx];
        }
        memcpy(old_buf, tmp_buf, sizeof(Elf64_Word) * symbol_idx);
        util_free(tmp_buf);
    }

    // Renumber the relocations
    for (int i = 1; i <= seg_count; i++)
    {                           // Map indicies in the segment table
        seg_data *pseg = SegData[i];
        pseg->SDsymidx = sym_map[pseg->SDsymidx];

        if (SecHdrTab[pseg->SDshtidx].sh_type == SHT_GROUP)
        {   // map symbol index of group section header
            unsigned oidx = SecHdrTab[pseg->SDshtidx].sh_info;
            assert(oidx < symbol_idx);
            // we only have one symbol table
            assert(SecHdrTab[pseg->SDshtidx].sh_link == SHN_SYMTAB);
            SecHdrTab[pseg->SDshtidx].sh_info = sym_map[oidx];
        }

        if (pseg->SDrel)
        {
            if (I64)
            {
                Elf64_Rela *rel = (Elf64_Rela *) pseg->SDrel->buf;
                for (int r = 0; r < pseg->SDrelcnt; r++)
                {
                    unsigned t = ELF64_R_TYPE(rel->r_info);
                    unsigned si = ELF64_R_SYM(rel->r_info);
                    assert(si < symbol_idx);
                    rel->r_info = ELF64_R_INFO(sym_map[si],t);
                    rel++;
                }
            }
            else
            {
                Elf32_Rel *rel = (Elf32_Rel *) pseg->SDrel->buf;
                assert(pseg->SDrelcnt == pseg->SDrel->size() / sizeof(Elf32_Rel));
                for (int r = 0; r < pseg->SDrelcnt; r++)
                {
                    unsigned t = ELF32_R_TYPE(rel->r_info);
                    unsigned si = ELF32_R_SYM(rel->r_info);
                    assert(si < symbol_idx);
                    rel->r_info = ELF32_R_INFO(sym_map[si],t);
                    rel++;
                }
            }
        }
    };

    return symtab;
}


/***************************
 * Fixup and terminate object file.
 */

void Obj::termfile()
{
    //dbg_printf("Obj::termfile\n");
    if (configv.addlinenumbers)
    {
        dwarf_termmodule();
    }
}

/*********************************
 * Terminate package.
 */

void Obj::term(const char *objfilename)
{
    //printf("Obj::term()\n");
#if SCPP
    if (!errcnt)
#endif
    {
        outfixlist();           // backpatches
    }

    if (configv.addlinenumbers)
    {
        dwarf_termfile();
    }

#if MARS
    if (!config.betterC)
        obj_rtinit();
#endif

#if SCPP
    if (errcnt)
        return;
#endif

    long foffset;
    Elf32_Shdr *sechdr;
    seg_data *seg;
    void *symtab = elf_renumbersyms();
    FILE *fd = NULL;

    int hdrsize = (I64 ? sizeof(Elf64_Ehdr) : sizeof(Elf32_Ehdr));

    uint16_t e_shnum;
    if (section_cnt < SHN_LORESERVE)
        e_shnum = section_cnt;
    else
    {
        e_shnum = SHN_UNDEF;
        SecHdrTab[0].sh_size = section_cnt;
    }
    // uint16_t e_shstrndx = SHN_SECNAMES;
    fobjbuf->writezeros(hdrsize);

            // Walk through sections determining size and file offsets
            // Sections will be output in the following order
            //  Null segment
            //  For each Code/Data Segment
            //      code/data to load
            //      relocations without addens
            //  .bss
            //  notes
            //  comments
            //  section names table
            //  symbol table
            //  strings table

    foffset = hdrsize;      // start after header
                                    // section header table at end

    //
    // First output individual section data associate with program
    //  code and data
    //
    //printf("Setup offsets and sizes foffset %d\n\tsection_cnt %d, seg_count %d\n",foffset,section_cnt,seg_count);
    for (int i=1; i<= seg_count; i++)
    {
        seg_data *pseg = SegData[i];
        Elf32_Shdr *sechdr = MAP_SEG2SEC(i);        // corresponding section
        if (sechdr->sh_addralign < pseg->SDalignment)
            sechdr->sh_addralign = pseg->SDalignment;
        foffset = elf_align(sechdr->sh_addralign,foffset);
        if (i == UDATA) // 0, BSS never allocated
        {   // but foffset as if it has
            sechdr->sh_offset = foffset;
            sechdr->sh_size = pseg->SDoffset;
                                // accumulated size
            continue;
        }
        else if (sechdr->sh_type == SHT_NOBITS) // .tbss never allocated
        {
            sechdr->sh_offset = foffset;
            sechdr->sh_size = pseg->SDoffset;
                                // accumulated size
            continue;
        }
        else if (!pseg->SDbuf)
            continue;           // For others leave sh_offset as 0

        sechdr->sh_offset = foffset;
        //printf("\tsection name %d,",sechdr->sh_name);
        if (pseg->SDbuf && pseg->SDbuf->size())
        {
            //printf(" - size %d\n",pseg->SDbuf->size());
            const size_t size = pseg->SDbuf->size();
            fobjbuf->write(pseg->SDbuf->buf, size);
            const long nfoffset = elf_align(sechdr->sh_addralign, foffset + size);
            sechdr->sh_size = nfoffset - foffset;
            foffset = nfoffset;
        }
        //printf(" assigned offset %d, size %d\n",foffset,sechdr->sh_size);
    }

    //
    // Next output any notes or comments
    //
    if (note_data)
    {
        sechdr = &SecHdrTab[secidx_note];               // Notes
        sechdr->sh_size = note_data->size();
        sechdr->sh_offset = foffset;
        fobjbuf->write(note_data->buf, sechdr->sh_size);
        foffset += sechdr->sh_size;
    }

    if (comment_data)
    {
        sechdr = &SecHdrTab[SHN_COM];           // Comments
        sechdr->sh_size = comment_data->size();
        sechdr->sh_offset = foffset;
        fobjbuf->write(comment_data->buf, sechdr->sh_size);
        foffset += sechdr->sh_size;
    }

    //
    // Then output string table for section names
    //
    sechdr = &SecHdrTab[SHN_SECNAMES];  // Section Names
    sechdr->sh_size = section_names->size();
    sechdr->sh_offset = foffset;
    //dbg_printf("section names offset %d\n",foffset);
    fobjbuf->write(section_names->buf, sechdr->sh_size);
    foffset += sechdr->sh_size;

    //
    // Symbol table and string table for symbols next
    //
    //dbg_printf("output symbol table size %d\n",SYMbuf->size());
    sechdr = &SecHdrTab[SHN_SYMTAB];    // Symbol Table
    sechdr->sh_size = SYMbuf->size();
    sechdr->sh_entsize = I64 ? sizeof(Elf64_Sym) : sizeof(Elf32_Sym);
    sechdr->sh_link = SHN_STRINGS;
    sechdr->sh_info = local_cnt;
    foffset = elf_align(4,foffset);
    sechdr->sh_offset = foffset;
    fobjbuf->write(symtab, sechdr->sh_size);
    foffset += sechdr->sh_size;
    util_free(symtab);

    if (shndx_data && shndx_data->size())
    {
        assert(section_cnt >= secidx_shndx);
        sechdr = &SecHdrTab[secidx_shndx];
        sechdr->sh_size = shndx_data->size();
        sechdr->sh_offset = foffset;
        fobjbuf->write(shndx_data->buf, sechdr->sh_size);
        foffset += sechdr->sh_size;
    }

    //dbg_printf("output section strings size 0x%x,offset 0x%x\n",symtab_strings->size(),foffset);
    sechdr = &SecHdrTab[SHN_STRINGS];   // Symbol Strings
    sechdr->sh_size = symtab_strings->size();
    sechdr->sh_offset = foffset;
    fobjbuf->write(symtab_strings->buf, sechdr->sh_size);
    foffset += sechdr->sh_size;

    //
    // Now the relocation data for program code and data sections
    //
    foffset = elf_align(4,foffset);
    //dbg_printf("output relocations size 0x%x, foffset 0x%x\n",section_names->size(),foffset);
    for (int i=1; i<= seg_count; i++)
    {
        seg = SegData[i];
        if (!seg->SDbuf)
        {
//            sechdr = &SecHdrTab[seg->SDrelidx];
//          if (I64 && sechdr->sh_type == SHT_RELA)
//              sechdr->sh_offset = foffset;
            continue;           // 0, BSS never allocated
        }
        if (seg->SDrel && seg->SDrel->size())
        {
            assert(seg->SDrelidx);
            sechdr = &SecHdrTab[seg->SDrelidx];
            sechdr->sh_size = seg->SDrel->size();
            sechdr->sh_offset = foffset;
            if (I64)
            {
                assert(seg->SDrelcnt == seg->SDrel->size() / sizeof(Elf64_Rela));
#ifdef DEBUG
                for (size_t i = 0; i < seg->SDrelcnt; ++i)
                {   Elf64_Rela *p = ((Elf64_Rela *)seg->SDrel->buf) + i;
                    if (ELF64_R_TYPE(p->r_info) == R_X86_64_64)
                        assert(*(Elf64_Xword *)(seg->SDbuf->buf + p->r_offset) == 0);
                }
#endif
            }
            else
                assert(seg->SDrelcnt == seg->SDrel->size() / sizeof(Elf32_Rel));
            fobjbuf->write(seg->SDrel->buf, sechdr->sh_size);
            foffset += sechdr->sh_size;
        }
    }

    //
    // Finish off with the section header table
    //
    uint64_t e_shoff = foffset;       // remember location in elf header
    //dbg_printf("output section header table\n");

    // Output the completed Section Header Table
    if (I64)
    {   // Translate section headers to 64 bits
        int sz = section_cnt * sizeof(Elf64_Shdr);
        fobjbuf->reserve(sz);
        for (int i = 0; i < section_cnt; i++)
        {
            Elf32_Shdr *p = SecHdrTab + i;
            Elf64_Shdr s;
            s.sh_name      = p->sh_name;
            s.sh_type      = p->sh_type;
            s.sh_flags     = p->sh_flags;
            s.sh_addr      = p->sh_addr;
            s.sh_offset    = p->sh_offset;
            s.sh_size      = p->sh_size;
            s.sh_link      = p->sh_link;
            s.sh_info      = p->sh_info;
            s.sh_addralign = p->sh_addralign;
            s.sh_entsize   = p->sh_entsize;
            fobjbuf->write(&s, sizeof(s));
        }
        foffset += sz;
    }
    else
    {
        fobjbuf->write(SecHdrTab, section_cnt * sizeof(Elf32_Shdr));
        foffset += section_cnt * sizeof(Elf32_Shdr);
    }

    //
    // Now that we have correct offset to section header table, e_shoff,
    //  go back and re-output the elf header
    //
    fobjbuf->position(0, hdrsize);
    if (I64)
    {
        static Elf64_Ehdr h =
        {
            {
                ELFMAG0,ELFMAG1,ELFMAG2,ELFMAG3,
                ELFCLASS64,             // EI_CLASS
                ELFDATA2LSB,            // EI_DATA
                EV_CURRENT,             // EI_VERSION
                ELFOSABI,0,             // EI_OSABI,EI_ABIVERSION
                0,0,0,0,0,0,0
            },
            ET_REL,                         // e_type
            EM_X86_64,                      // e_machine
            EV_CURRENT,                     // e_version
            0,                              // e_entry
            0,                              // e_phoff
            0,                              // e_shoff
            0,                              // e_flags
            sizeof(Elf64_Ehdr),             // e_ehsize
            sizeof(Elf64_Phdr),             // e_phentsize
            0,                              // e_phnum
            sizeof(Elf64_Shdr),             // e_shentsize
            0,                              // e_shnum
            SHN_SECNAMES                    // e_shstrndx
        };
        h.e_shoff     = e_shoff;
        h.e_shnum     = e_shnum;
        fobjbuf->write(&h, hdrsize);
    }
    else
    {
        static Elf32_Ehdr h =
        {
            {
                ELFMAG0,ELFMAG1,ELFMAG2,ELFMAG3,
                ELFCLASS32,             // EI_CLASS
                ELFDATA2LSB,            // EI_DATA
                EV_CURRENT,             // EI_VERSION
                ELFOSABI,0,             // EI_OSABI,EI_ABIVERSION
                0,0,0,0,0,0,0
            },
            ET_REL,                         // e_type
            EM_386,                         // e_machine
            EV_CURRENT,                     // e_version
            0,                              // e_entry
            0,                              // e_phoff
            0,                              // e_shoff
            0,                              // e_flags
            sizeof(Elf32_Ehdr),             // e_ehsize
            sizeof(Elf32_Phdr),             // e_phentsize
            0,                              // e_phnum
            sizeof(Elf32_Shdr),             // e_shentsize
            0,                              // e_shnum
            SHN_SECNAMES                    // e_shstrndx
        };
        h.e_shoff     = e_shoff;
        h.e_shnum     = e_shnum;
        fobjbuf->write(&h, hdrsize);
    }
    fobjbuf->position(foffset, 0);
    fobjbuf->flush();
}

/*****************************
 * Line number support.
 */

/***************************
 * Record file and line number at segment and offset.
 * The actual .debug_line segment is put out by dwarf_termfile().
 * Params:
 *      srcpos = source file position
 *      seg = segment it corresponds to
 *      offset = offset within seg
 */

void Obj::linnum(Srcpos srcpos, int seg, targ_size_t offset)
{
    if (srcpos.Slinnum == 0)
        return;

#if 0
#if MARS || SCPP
    printf("Obj::linnum(seg=%d, offset=0x%lx) ", seg, offset);
#endif
    srcpos.print("");
#endif

#if MARS
    if (!srcpos.Sfilename)
        return;
#endif
#if SCPP
    if (!srcpos.Sfilptr)
        return;
    sfile_debug(&srcpos_sfile(srcpos));
    Sfile *sf = *srcpos.Sfilptr;
#endif

    size_t i;
    seg_data *pseg = SegData[seg];

    // Find entry i in SDlinnum_data[] that corresponds to srcpos filename
    for (i = 0; 1; i++)
    {
        if (i == pseg->SDlinnum_count)
        {   // Create new entry
            if (pseg->SDlinnum_count == pseg->SDlinnum_max)
            {   // Enlarge array
                unsigned newmax = pseg->SDlinnum_max * 2 + 1;
                //printf("realloc %d\n", newmax * sizeof(linnum_data));
                pseg->SDlinnum_data = (linnum_data *)mem_realloc(
                    pseg->SDlinnum_data, newmax * sizeof(linnum_data));
                memset(pseg->SDlinnum_data + pseg->SDlinnum_max, 0,
                    (newmax - pseg->SDlinnum_max) * sizeof(linnum_data));
                pseg->SDlinnum_max = newmax;
            }
            pseg->SDlinnum_count++;
#if MARS
            pseg->SDlinnum_data[i].filename = srcpos.Sfilename;
#endif
#if SCPP
            pseg->SDlinnum_data[i].filptr = sf;
#endif
            break;
        }
#if MARS
        if (pseg->SDlinnum_data[i].filename == srcpos.Sfilename)
#endif
#if SCPP
        if (pseg->SDlinnum_data[i].filptr == sf)
#endif
            break;
    }

    linnum_data *ld = &pseg->SDlinnum_data[i];
//    printf("i = %d, ld = x%x\n", i, ld);
    if (ld->linoff_count == ld->linoff_max)
    {
        if (!ld->linoff_max)
            ld->linoff_max = 8;
        ld->linoff_max *= 2;
        ld->linoff = (unsigned (*)[2])mem_realloc(ld->linoff, ld->linoff_max * sizeof(unsigned) * 2);
    }
    ld->linoff[ld->linoff_count][0] = srcpos.Slinnum;
    ld->linoff[ld->linoff_count][1] = offset;
    ld->linoff_count++;
}


/*******************************
 * Set start address
 */

void Obj::startaddress(Symbol *s)
{
    //dbg_printf("Obj::startaddress(Symbol *%s)\n",s->Sident);
    //obj.startaddress = s;
}

/*******************************
 * Output library name.
 */

bool Obj::includelib(const char *name)
{
    //dbg_printf("Obj::includelib(name *%s)\n",name);
    return false;
}

/**********************************
 * Do we allow zero sized objects?
 */

bool Obj::allowZeroSize()
{
    return true;
}

/**************************
 * Embed string in executable.
 */

void Obj::exestr(const char *p)
{
    //dbg_printf("Obj::exestr(char *%s)\n",p);
}

/**************************
 * Embed string in obj.
 */

void Obj::user(const char *p)
{
    //dbg_printf("Obj::user(char *%s)\n",p);
}

/*******************************
 * Output a weak extern record.
 */

void Obj::wkext(Symbol *s1,Symbol *s2)
{
    //dbg_printf("Obj::wkext(Symbol *%s,Symbol *s2)\n",s1->Sident,s2->Sident);
}

/*******************************
 * Output file name record.
 *
 * Currently assumes that obj_filename will not be called
 *      twice for the same file.
 */

void obj_filename(const char *modname)
{
    //dbg_printf("obj_filename(char *%s)\n",modname);
    unsigned strtab_idx = Obj::addstr(symtab_strings,modname);
    elf_addsym(strtab_idx,0,0,STT_FILE,STB_LOCAL,SHN_ABS);
}

/*******************************
 * Embed compiler version in .obj file.
 */

void Obj::compiler()
{
    //dbg_printf("Obj::compiler\n");
    comment_data = new Outbuffer();
    comment_data->write(::compiler,sizeof(::compiler));
    //dbg_printf("Comment data size %d\n",comment_data->size());
}


/**************************************
 * Symbol is the function that calls the static constructors.
 * Put a pointer to it into a special segment that the startup code
 * looks at.
 * Input:
 *      s       static constructor function
 *      dtor    !=0 if leave space for static destructor
 *      seg     1:      user
 *              2:      lib
 *              3:      compiler
 */

void Obj::staticctor(Symbol *s,int dtor,int none)
{
    // Static constructors and destructors
    //dbg_printf("Obj::staticctor(%s) offset %x\n",s->Sident,s->Soffset);
    //symbol_print(s);
    const IDXSEC seg = s->Sseg =
        ElfObj::getsegment(".ctors", NULL, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE, 4);
    const unsigned relinfo = I64 ? R_X86_64_64 : R_386_32;
    const size_t sz = ElfObj::writerel(seg, SegData[seg]->SDoffset, relinfo, STI_TEXT, s->Soffset);
    SegData[seg]->SDoffset += sz;
}

/**************************************
 * Symbol is the function that calls the static destructors.
 * Put a pointer to it into a special segment that the exit code
 * looks at.
 * Input:
 *      s       static destructor function
 */

void Obj::staticdtor(Symbol *s)
{
    //dbg_printf("Obj::staticdtor(%s) offset %x\n",s->Sident,s->Soffset);
    //symbol_print(s);
    // Why does this sequence differ from staticctor, looks like a bug?
    const IDXSEC seg =
        ElfObj::getsegment(".dtors", NULL, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE, 4);
    const unsigned relinfo = I64 ? R_X86_64_64 : R_386_32;
    const size_t sz = ElfObj::writerel(seg, SegData[seg]->SDoffset, relinfo, s->Sxtrnnum, s->Soffset);
    SegData[seg]->SDoffset += sz;
}

/***************************************
 * Stuff pointer to function in its own segment.
 * Used for static ctor and dtor lists.
 */

void Obj::setModuleCtorDtor(Symbol *s, bool isCtor)
{
    //dbg_printf("Obj::setModuleCtorDtor(%s) \n",s->Sident);
}


/***************************************
 * Stuff the following data in a separate segment:
 *      pointer to function
 *      pointer to ehsym
 *      length of function
 */

void Obj::ehtables(Symbol *sfunc,targ_size_t size,Symbol *ehsym)
{
    assert(0);                  // converted to Dwarf EH debug format
}

/*********************************************
 * Don't need to generate section brackets, use __start_SEC/__stop_SEC instead.
 */

void Obj::ehsections()
{
    obj_tlssections();
}

/*********************************************
 * Put out symbols that define the beginning/end of the thread local storage sections.
 */

STATIC void obj_tlssections()
{
    IDXSTR namidx;
    int align = I64 ? 16 : 4;

    int sec = ElfObj::getsegment(".tdata", NULL, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE|SHF_TLS, align);
    Obj::bytes(sec, 0, align, NULL);

    namidx = Obj::addstr(symtab_strings,"_tlsstart");
    elf_addsym(namidx, 0, align, STT_TLS, STB_GLOBAL, MAP_SEG2SECIDX(sec));

    ElfObj::getsegment(".tdata.", NULL, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE|SHF_TLS, align);

    sec = ElfObj::getsegment(".tcommon", NULL, SHT_NOBITS, SHF_ALLOC|SHF_WRITE|SHF_TLS, align);
    namidx = Obj::addstr(symtab_strings,"_tlsend");
    elf_addsym(namidx, 0, align, STT_TLS, STB_GLOBAL, MAP_SEG2SECIDX(sec));
}

/*********************************
 * Setup for Symbol s to go into a COMDAT segment.
 * Output (if s is a function):
 *      cseg            segment index of new current code segment
 *      Offset(cseg)         starting offset in cseg
 * Returns:
 *      "segment index" of COMDAT
 * References:
 *      Section Groups http://www.sco.com/developers/gabi/2003-12-17/ch4.sheader.html#section_groups
 *      COMDAT section groups https://www.airs.com/blog/archives/52
 */

STATIC void setup_comdat(Symbol *s)
{
    const char *prefix;
    int type;
    int flags;
    int align = 4;

    //printf("Obj::comdat(Symbol *%s\n",s->Sident);
    //symbol_print(s);
    symbol_debug(s);
    if (tyfunc(s->ty()))
    {
#if !ELF_COMDAT
        prefix = ".text.";              // undocumented, but works
        type = SHT_PROGBITS;
        flags = SHF_ALLOC|SHF_EXECINSTR;
#else
        reset_symbuf->write(&s, sizeof(s));

        const char *p = cpp_mangle(s);

        bool added = false;
        IDXSTR namidx = elf_addsectionname(".text.", p, &added);
        int groupseg;
        if (added)
        {
            // Create a new COMDAT section group
            const IDXSTR grpnamidx = elf_addsectionname(".group");
            groupseg = elf_addsegment(grpnamidx, SHT_GROUP, 0, sizeof(IDXSYM));
            MAP_SEG2SEC(groupseg)->sh_link = SHN_SYMTAB;
            MAP_SEG2SEC(groupseg)->sh_entsize = sizeof(IDXSYM);
            // Create a new TEXT section for the comdat symbol with the SHF_GROUP bit set
            s->Sseg = elf_addsegment(namidx, SHT_PROGBITS, SHF_ALLOC|SHF_EXECINSTR|SHF_GROUP, align);
            // add TEXT section to COMDAT section group
            SegData[groupseg]->SDbuf->write32(GRP_COMDAT);
            SegData[groupseg]->SDbuf->write32(MAP_SEG2SECIDX(s->Sseg));
            SegData[s->Sseg]->SDassocseg = groupseg;
        }
        else
        {
            /* If the section already existed, we've hit one of the few
             * occurences of different symbols with identical mangling. This should
             * not happen, but as a workaround we just use the existing sections.
             * Also see https://issues.dlang.org/show_bug.cgi?id=17352,
             * https://issues.dlang.org/show_bug.cgi?id=14831, and
             * https://issues.dlang.org/show_bug.cgi?id=17339.
             */
            s->Sseg = elf_getsegment(namidx);
            groupseg = SegData[s->Sseg]->SDassocseg;
            assert(groupseg);
        }

        // Create a weak symbol for the comdat
        namidx = Obj::addstr(symtab_strings, p);
        s->Sxtrnnum = elf_addsym(namidx, 0, 0, STT_FUNC, STB_WEAK, MAP_SEG2SECIDX(s->Sseg));

        if (added)
        {
            /* Set the weak symbol as comdat group symbol. This symbol determines
             * whether all or none of the sections in the group get linked. It's
             * also the only symbol in all group sections that might be referenced
             * from outside of the group.
             */
            MAP_SEG2SEC(groupseg)->sh_info = s->Sxtrnnum;
            SegData[s->Sseg]->SDsym = s;
        }
        else
        {
            // existing group symbol, and section symbol
            assert(MAP_SEG2SEC(groupseg)->sh_info);
            assert(MAP_SEG2SEC(groupseg)->sh_info == SegData[s->Sseg]->SDsym->Sxtrnnum);
        }
        if (s->Salignment > align)
            SegData[s->Sseg]->SDalignment = s->Salignment;
        return;
#endif
    }
    else if ((s->ty() & mTYLINK) == mTYthread)
    {
        /* Ensure that ".tdata" precedes any other .tdata. section, as the ld
         * linker script fails to work right.
         */
        if (I64)
            align = 16;
        ElfObj::getsegment(".tdata", NULL, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE|SHF_TLS, align);

        s->Sfl = FLtlsdata;
        prefix = ".tdata.";
        type = SHT_PROGBITS;
        flags = SHF_ALLOC|SHF_WRITE|SHF_TLS;
    }
    else
    {
        if (I64)
            align = 16;
        s->Sfl = FLdata;
        //prefix = ".gnu.linkonce.d.";
        prefix = ".data.";
        type = SHT_PROGBITS;
        flags = SHF_ALLOC|SHF_WRITE;
    }

    s->Sseg = ElfObj::getsegment(prefix, cpp_mangle(s), type, flags, align);
                                // find or create new segment
    if (s->Salignment > align)
        SegData[s->Sseg]->SDalignment = s->Salignment;
    SegData[s->Sseg]->SDsym = s;
}

int Obj::comdat(Symbol *s)
{
    setup_comdat(s);
    if (s->Sfl == FLdata || s->Sfl == FLtlsdata)
    {
        Obj::pubdef(s->Sseg,s,0);
        searchfixlist(s);               // backpatch any refs to this symbol
    }
    return s->Sseg;
}

int Obj::comdatsize(Symbol *s, targ_size_t symsize)
{
    setup_comdat(s);
    if (s->Sfl == FLdata || s->Sfl == FLtlsdata)
    {
        Obj::pubdefsize(s->Sseg,s,0,symsize);
        searchfixlist(s);               // backpatch any refs to this symbol
    }
    s->Soffset = 0;
    return s->Sseg;
}

int Obj::readonly_comdat(Symbol *s)
{
    assert(0);
    return 0;
}

int Obj::jmpTableSegment(Symbol *s)
{
    segidx_t seg = jmpseg;
    if (seg)                            // memoize the jmpseg on a per-function basis
        return seg;

    if (config.flags & CFGromable)
        seg = cseg;
    else
    {
        seg_data *pseg = SegData[s->Sseg];
        if (pseg->SDassocseg)
        {
            /* `s` is in a COMDAT, so the jmp table segment must also
             * go into its own segment in the same group.
             */
            seg = ElfObj::getsegment(".rodata.", s->Sident, SHT_PROGBITS, SHF_ALLOC|SHF_GROUP, NPTRSIZE);
            addSegmentToComdat(seg, s->Sseg);
        }
        else
            seg = CDATA;
    }
    jmpseg = seg;
    return seg;
}

/****************************************
 * If `comdatseg` has a group, add `secidx` to the group.
 * Params:
 *      secidx = section to add to the group
 *      comdatseg = comdat that started the group
 */

static void addSectionToComdat(IDXSEC secidx, segidx_t comdatseg)
{
    seg_data *pseg = SegData[comdatseg];
    segidx_t groupseg = pseg->SDassocseg;
    if (groupseg)
    {
        seg_data *pgroupseg = SegData[groupseg];

        /* Don't write it if it is already there
         */
        Outbuffer *buf = pgroupseg->SDbuf;
        assert(sizeof(int) == 4);               // loop depends on this
        for (size_t i = buf->size(); i > 4;)
        {
            /* A linear search, but shouldn't be more than 4 items
             * in it.
             */
            i -= 4;
            if (*(int*)(buf->buf + i) == secidx)
                return;
        }
        buf->write32(secidx);
    }
}

/***********************************
 * Returns:
 *      jump table segment for function s
 */
void addSegmentToComdat(segidx_t seg, segidx_t comdatseg)
{
    addSectionToComdat(SegData[seg]->SDshtidx, comdatseg);
}

static int elf_addsegment2(IDXSEC shtidx, IDXSYM symidx, IDXSEC relidx)
{
    //printf("SegData = %p\n", SegData);
    int seg = ++seg_count;
    if (seg_count >= seg_max)
    {                           // need more room in segment table
        seg_max += OB_SEG_INC;
        SegData = (seg_data **)mem_realloc(SegData,seg_max * sizeof(seg_data *));
        memset(&SegData[seg_count], 0, (seg_max - seg_count) * sizeof(seg_data *));
    }
    assert(seg_count < seg_max);
    if (!SegData[seg])
    {   SegData[seg] = (seg_data *)mem_calloc(sizeof(seg_data));
        //printf("test2: SegData[%d] = %p\n", seg, SegData[seg]);
    }

    seg_data *pseg = SegData[seg];
    pseg->SDseg = seg;
    pseg->SDshtidx = shtidx;
    pseg->SDoffset = 0;
    if (pseg->SDbuf)
        pseg->SDbuf->setsize(0);
    else
    {   if (SecHdrTab[shtidx].sh_type != SHT_NOBITS)
        {   pseg->SDbuf = new Outbuffer(OB_XTRA_STR);
            pseg->SDbuf->reserve(1024);
        }
    }
    if (pseg->SDrel)
        pseg->SDrel->setsize(0);
    pseg->SDsymidx = symidx;
    pseg->SDrelidx = relidx;
    pseg->SDrelmaxoff = 0;
    pseg->SDrelindex = 0;
    pseg->SDrelcnt = 0;
    pseg->SDshtidxout = 0;
    pseg->SDsym = NULL;
    pseg->SDaranges_offset = 0;
    pseg->SDlinnum_count = 0;
    return seg;
}

/********************************
 * Add a new section and get corresponding seg_data entry.
 *
 * Input:
 *     nameidx = string index of section name
 *        type = section header type, e.g. SHT_PROGBITS
 *       flags = section header flags, e.g. SHF_ALLOC
 *       align = section alignment
 * Returns:
 *      SegData index of newly created section.
 */
static int elf_addsegment(IDXSTR namidx, int type, int flags, int align)
{
    //dbg_printf("\tNew segment - %d size %d\n", seg,SegData[seg]->SDbuf);
    IDXSEC shtidx = elf_newsection2(namidx,type,flags,0,0,0,0,0,0,0);
    SecHdrTab[shtidx].sh_addralign = align;
    IDXSYM symidx = elf_addsym(0, 0, 0, STT_SECTION, STB_LOCAL, shtidx);
    int seg = elf_addsegment2(shtidx, symidx, 0);
    //printf("-ElfObj::getsegment() = %d\n", seg);
    return seg;
}

/********************************
 * Find corresponding seg_data entry for existing section.
 *
 * Input:
 *     nameidx = string index of section name
 * Returns:
 *      SegData index of found section or 0 if none was found.
 */
static int elf_getsegment(IDXSTR namidx)
{
    // find existing section
    for (int seg = CODE; seg <= seg_count; seg++)
    {                               // should be in segment table
        if (MAP_SEG2SEC(seg)->sh_name == namidx)
        {
            return seg;             // found section for segment
        }
    }
    return 0;
}

/********************************
 * Get corresponding seg_data entry for an existing or newly added section.
 *
 * Input:
 *        name = name of section
 *      suffix = append to name
 *        type = section header type, e.g. SHT_PROGBITS
 *       flags = section header flags, e.g. SHF_ALLOC
 *       align = section alignment
 * Returns:
 *      SegData index of found or newly created section.
 */
int ElfObj::getsegment(const char *name, const char *suffix, int type, int flags,
        int align)
{
    //printf("ElfObj::getsegment(%s,%s,flags %x, align %d)\n",name,suffix,flags,align);
    bool added = false;
    IDXSEC namidx = elf_addsectionname(name, suffix, &added);
    if (!added)
    {
        int seg = elf_getsegment(namidx);
        assert(seg);
        return seg;
    }
    return elf_addsegment(namidx, type, flags, align);
}

/**********************************
 * Reset code seg to existing seg.
 * Used after a COMDAT for a function is done.
 */

void Obj::setcodeseg(int seg)
{
    cseg = seg;
}

/********************************
 * Define a new code segment.
 * Input:
 *      name            name of segment, if NULL then revert to default
 *      suffix  0       use name as is
 *              1       append "_TEXT" to name
 * Output:
 *      cseg            segment index of new current code segment
 *      Offset(cseg)         starting offset in cseg
 * Returns:
 *      segment index of newly created code segment
 */

int Obj::codeseg(char *name,int suffix)
{
    int seg;
    const char *sfx;

    //dbg_printf("Obj::codeseg(%s,%x)\n",name,suffix);

    sfx = (suffix) ? "_TEXT" : NULL;

    if (!name)                          // returning to default code segment
    {
        if (cseg != CODE)               // not the current default
        {
            SegData[cseg]->SDoffset = Offset(cseg);
            Offset(cseg) = SegData[CODE]->SDoffset;
            cseg = CODE;
        }
        return cseg;
    }

    seg = ElfObj::getsegment(name, sfx, SHT_PROGBITS, SHF_ALLOC|SHF_EXECINSTR, 4);
                                    // find or create code segment

    cseg = seg;                         // new code segment index
    Offset(cseg) = 0;

    return seg;
}

/*********************************
 * Define segments for Thread Local Storage.
 * Here's what the elf tls spec says:
 *      Field           .tbss                   .tdata
 *      sh_name         .tbss                   .tdata
 *      sh_type         SHT_NOBITS              SHT_PROGBITS
 *      sh_flags        SHF_ALLOC|SHF_WRITE|    SHF_ALLOC|SHF_WRITE|
 *                      SHF_TLS                 SHF_TLS
 *      sh_addr         virtual addr of section virtual addr of section
 *      sh_offset       0                       file offset of initialization image
 *      sh_size         size of section         size of section
 *      sh_link         SHN_UNDEF               SHN_UNDEF
 *      sh_info         0                       0
 *      sh_addralign    alignment of section    alignment of section
 *      sh_entsize      0                       0
 * We want _tlsstart and _tlsend to bracket all the D tls data.
 * The default linker script (ld -verbose) says:
 *  .tdata      : { *(.tdata .tdata.* .gnu.linkonce.td.*) }
 *  .tbss       : { *(.tbss .tbss.* .gnu.linkonce.tb.*) *(.tcommon) }
 * so if we assign names:
 *      _tlsstart .tdata
 *      symbols   .tdata.
 *      symbols   .tbss
 *      _tlsend   .tbss.
 * this should work.
 * Don't care about sections emitted by other languages, as we presume they
 * won't be storing D gc roots in their tls.
 * Output:
 *      seg_tlsseg      set to segment number for TLS segment.
 * Returns:
 *      segment for TLS segment
 */

seg_data *Obj::tlsseg()
{
    /* Ensure that ".tdata" precedes any other .tdata. section, as the ld
     * linker script fails to work right.
     */
    ElfObj::getsegment(".tdata", NULL, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE|SHF_TLS, 4);

    static const char tlssegname[] = ".tdata.";
    //dbg_printf("Obj::tlsseg(\n");

    if (seg_tlsseg == UNKNOWN)
    {
        seg_tlsseg = ElfObj::getsegment(tlssegname, NULL, SHT_PROGBITS,
            SHF_ALLOC|SHF_WRITE|SHF_TLS, I64 ? 16 : 4);
    }
    return SegData[seg_tlsseg];
}


/*********************************
 * Define segments for Thread Local Storage.
 * Output:
 *      seg_tlsseg_bss  set to segment number for TLS segment.
 * Returns:
 *      segment for TLS segment
 */

seg_data *Obj::tlsseg_bss()
{
    static const char tlssegname[] = ".tbss";
    //dbg_printf("Obj::tlsseg_bss(\n");

    if (seg_tlsseg_bss == UNKNOWN)
    {
        seg_tlsseg_bss = ElfObj::getsegment(tlssegname, NULL, SHT_NOBITS,
            SHF_ALLOC|SHF_WRITE|SHF_TLS, I64 ? 16 : 4);
    }
    return SegData[seg_tlsseg_bss];
}

seg_data *Obj::tlsseg_data()
{
    // specific for Mach-O
    assert(0);
    return NULL;
}


/*******************************
 * Output an alias definition record.
 */

void Obj::_alias(const char *n1,const char *n2)
{
    dbg_printf("Obj::_alias(%s,%s)\n",n1,n2);
    assert(0);
#if NOT_DONE
    char *buffer = (char *) alloca(strlen(n1) + strlen(n2) + 2 * ONS_OHD);
    unsigned len = obj_namestring(buffer,n1);
    len += obj_namestring(buffer + len,n2);
    objrecord(ALIAS,buffer,len);
#endif
}

char *unsstr(unsigned value)
{
    static char buffer[64];

    sprintf(buffer, "%d", value);
    return buffer;
}

/*******************************
 * Mangle a name.
 * Returns:
 *      mangled name
 */

char *obj_mangle2(Symbol *s,char *dest, size_t *destlen)
{
    char *name;

    //dbg_printf("Obj::mangle('%s'), mangle = x%x\n",s->Sident,type_mangle(s->Stype));
    symbol_debug(s);
    assert(dest);
#if SCPP
    name = CPP ? cpp_mangle(s) : s->Sident;
#elif MARS
    name = cpp_mangle(s);
#else
    name = s->Sident;
#endif
    size_t len = strlen(name);                 // # of bytes in name
    //dbg_printf("len %d\n",len);
    switch (type_mangle(s->Stype))
    {
        case mTYman_pas:                // if upper case
        case mTYman_for:
            if (len >= DEST_LEN)
                dest = (char *)mem_malloc(len + 1);
            memcpy(dest,name,len + 1);  // copy in name and ending 0
            for (int i = 0; 1; i++)
            {   char c = dest[i];
                if (!c)
                    break;
                if (c >= 'a' && c <= 'z')
                    dest[i] = c + 'A' - 'a';
            }
            break;
        case mTYman_std:
#if TARGET_LINUX || TARGET_FREEBSD || TARGET_OPENBSD || TARGET_SOLARIS
            if (tyfunc(s->ty()) && !variadic(s->Stype))
#else
            if (!(config.flags4 & CFG4oldstdmangle) &&
                config.exe == EX_WIN32 && tyfunc(s->ty()) &&
                !variadic(s->Stype))
#endif
            {
                char *pstr = unsstr(type_paramsize(s->Stype));
                size_t pstrlen = strlen(pstr);
                size_t dlen = len + 1 + pstrlen;

                if (dlen >= DEST_LEN)
                    dest = (char *)mem_malloc(dlen + 1);
                memcpy(dest,name,len);
                dest[len] = '@';
                memcpy(dest + 1 + len, pstr, pstrlen + 1);
                len = dlen;
                break;
            }
        case mTYman_cpp:
        case mTYman_c:
        case mTYman_d:
        case mTYman_sys:
        case 0:
            if (len >= DEST_LEN)
                dest = (char *)mem_malloc(len + 1);
            memcpy(dest,name,len+1);// copy in name and trailing 0
            break;

        default:
#ifdef DEBUG
            printf("mangling %x\n",type_mangle(s->Stype));
            symbol_print(s);
#endif
            printf("%d\n", type_mangle(s->Stype));
            assert(0);
    }
    //dbg_printf("\t %s\n",dest);
    *destlen = len;
    return dest;
}

/*******************************
 * Export a function name.
 */

void Obj::export_symbol(Symbol *s,unsigned argsize)
{
    //dbg_printf("Obj::export_symbol(%s,%d)\n",s->Sident,argsize);
}

/*******************************
 * Update data information about symbol
 *      align for output and assign segment
 *      if not already specified.
 *
 * Input:
 *      sdata           data symbol
 *      datasize        output size
 *      seg             default seg if not known
 * Returns:
 *      actual seg
 */

int Obj::data_start(Symbol *sdata, targ_size_t datasize, int seg)
{
    targ_size_t alignbytes;
    //printf("Obj::data_start(%s,size %llx,seg %d)\n",sdata->Sident,datasize,seg);
    //symbol_print(sdata);

    if (sdata->Sseg == UNKNOWN) // if we don't know then there
        sdata->Sseg = seg;      // wasn't any segment override
    else
        seg = sdata->Sseg;
    targ_size_t offset = Offset(seg);
    if (sdata->Salignment > 0)
    {   if (SegData[seg]->SDalignment < sdata->Salignment)
            SegData[seg]->SDalignment = sdata->Salignment;
        alignbytes = ((offset + sdata->Salignment - 1) & ~(sdata->Salignment - 1)) - offset;
    }
    else
        alignbytes = _align(datasize, offset) - offset;
    if (alignbytes)
        Obj::lidata(seg, offset, alignbytes);
    sdata->Soffset = offset + alignbytes;
    return seg;
}

/*******************************
 * Update function info before codgen
 *
 * If code for this function is in a different segment
 * than the current default in cseg, switch cseg to new segment.
 */

void Obj::func_start(Symbol *sfunc)
{
    //dbg_printf("Obj::func_start(%s)\n",sfunc->Sident);
    symbol_debug(sfunc);

    if ((tybasic(sfunc->ty()) == TYmfunc) && (sfunc->Sclass == SCextern))
    {                                   // create a new code segment
        sfunc->Sseg =
            ElfObj::getsegment(".gnu.linkonce.t.", cpp_mangle(sfunc), SHT_PROGBITS, SHF_ALLOC|SHF_EXECINSTR,4);

    }
    else if (sfunc->Sseg == UNKNOWN)
        sfunc->Sseg = CODE;
    //dbg_printf("sfunc->Sseg %d CODE %d cseg %d Coffset %d\n",sfunc->Sseg,CODE,cseg,Offset(cseg));
    cseg = sfunc->Sseg;
    jmpseg = 0;                         // only 1 jmp seg per function
    assert(cseg == CODE || cseg > COMD);
#if ELF_COMDAT
    if (!symbol_iscomdat(sfunc))
#endif
        Obj::pubdef(cseg, sfunc, Offset(cseg));
    sfunc->Soffset = Offset(cseg);

    dwarf_func_start(sfunc);
}

/*******************************
 * Update function info after codgen
 */

void Obj::func_term(Symbol *sfunc)
{
    //dbg_printf("Obj::func_term(%s) offset %x, Coffset %x symidx %d\n",
//          sfunc->Sident, sfunc->Soffset,Offset(cseg),sfunc->Sxtrnnum);

    // fill in the function size
    if (I64)
        SymbolTable64[sfunc->Sxtrnnum].st_size = Offset(cseg) - sfunc->Soffset;
    else
        SymbolTable[sfunc->Sxtrnnum].st_size = Offset(cseg) - sfunc->Soffset;
    dwarf_func_term(sfunc);
}

/********************************
 * Output a public definition.
 * Input:
 *      seg =           segment index that symbol is defined in
 *      s ->            symbol
 *      offset =        offset of name within segment
 */

void Obj::pubdef(int seg, Symbol *s, targ_size_t offset)
{
    const targ_size_t symsize=
        tyfunc(s->ty()) ? Offset(s->Sseg) - offset : type_size(s->Stype);
    Obj::pubdefsize(seg, s, offset, symsize);
}

/********************************
 * Output a public definition.
 * Input:
 *      seg =           segment index that symbol is defined in
 *      s ->            symbol
 *      offset =        offset of name within segment
 *      symsize         size of symbol
 */

void Obj::pubdefsize(int seg, Symbol *s, targ_size_t offset, targ_size_t symsize)
{
    int bind;
    switch (s->Sclass)
    {
        case SCglobal:
        case SCinline:
            bind = STB_GLOBAL;
            break;
        case SCcomdat:
        case SCcomdef:
            bind = STB_WEAK;
            break;
        default:
            bind = STB_LOCAL;
            break;
    }

#if 0
    //printf("\nObj::pubdef(%d,%s,%d)\n",seg,s->Sident,offset);
    //symbol_print(s);
#endif

    symbol_debug(s);
    reset_symbuf->write(&s, sizeof(s));
    IDXSTR namidx = elf_addmangled(s);
    //printf("\tnamidx %d,section %d\n",namidx,MAP_SEG2SECIDX(seg));
    if (tyfunc(s->ty()))
    {
        s->Sxtrnnum = elf_addsym(namidx, offset, symsize,
            STT_FUNC, bind, MAP_SEG2SECIDX(seg));
    }
    else
    {
        const unsigned typ = (s->ty() & mTYthread) ? STT_TLS : STT_OBJECT;
        s->Sxtrnnum = elf_addsym(namidx, offset, symsize,
            typ, bind, MAP_SEG2SECIDX(seg));
    }
}

/*******************************
 * Output an external symbol for name.
 * Input:
 *      name    Name to do EXTDEF on
 *              (Not to be mangled)
 * Returns:
 *      Symbol table index of the definition
 *      NOTE: Numbers will not be linear.
 */

int Obj::external_def(const char *name)
{
    //dbg_printf("Obj::external_def('%s')\n",name);
    assert(name);
    IDXSTR namidx = Obj::addstr(symtab_strings,name);
    IDXSYM symidx = elf_addsym(namidx, 0, 0, STT_NOTYPE, STB_GLOBAL, SHN_UNDEF);
    return symidx;
}


/*******************************
 * Output an external for existing symbol.
 * Input:
 *      s       Symbol to do EXTDEF on
 *              (Name is to be mangled)
 * Returns:
 *      Symbol table index of the definition
 *      NOTE: Numbers will not be linear.
 */

int Obj::external(Symbol *s)
{
    int symtype,sectype;
    unsigned size;

    //dbg_printf("Obj::external('%s') %x\n",s->Sident,s->Svalue);
    symbol_debug(s);
    reset_symbuf->write(&s, sizeof(s));
    IDXSTR namidx = elf_addmangled(s);

#if SCPP
    if (s->Sscope && !tyfunc(s->ty()))
    {
        symtype = STT_OBJECT;
        sectype = SHN_COMMON;
        size = type_size(s->Stype);
    }
    else
#endif
    {
        symtype = STT_NOTYPE;
        sectype = SHN_UNDEF;
        size = 0;
    }
    if (s->ty() & mTYthread)
    {
        //printf("Obj::external('%s') %x TLS\n",s->Sident,s->Svalue);
        symtype = STT_TLS;
    }

    s->Sxtrnnum = elf_addsym(namidx, size, size, symtype,
        /*(s->ty() & mTYweak) ? STB_WEAK : */STB_GLOBAL, sectype);
    return s->Sxtrnnum;

}

/*******************************
 * Output a common block definition.
 * Input:
 *      p ->    external identifier
 *      size    size in bytes of each elem
 *      count   number of elems
 * Returns:
 *      Symbol table index for symbol
 */

int Obj::common_block(Symbol *s,targ_size_t size,targ_size_t count)
{
    //printf("Obj::common_block('%s',%d,%d)\n",s->Sident,size,count);
    symbol_debug(s);

    int align = I64 ? 16 : 4;
    if (s->ty() & mTYthread)
    {
        s->Sseg = ElfObj::getsegment(".tbss.", cpp_mangle(s),
                SHT_NOBITS, SHF_ALLOC|SHF_WRITE|SHF_TLS, align);
        s->Sfl = FLtlsdata;
        SegData[s->Sseg]->SDsym = s;
        SegData[s->Sseg]->SDoffset += size * count;
        Obj::pubdefsize(s->Sseg, s, 0, size * count);
        searchfixlist(s);
        return s->Sseg;
    }
    else
    {
        s->Sseg = ElfObj::getsegment(".bss.", cpp_mangle(s),
                SHT_NOBITS, SHF_ALLOC|SHF_WRITE, align);
        s->Sfl = FLudata;
        SegData[s->Sseg]->SDsym = s;
        SegData[s->Sseg]->SDoffset += size * count;
        Obj::pubdefsize(s->Sseg, s, 0, size * count);
        searchfixlist(s);
        return s->Sseg;
    }
#if 0
    reset_symbuf->write(s);
    IDXSTR namidx = elf_addmangled(s);
    alignOffset(UDATA,size);
    IDXSYM symidx = elf_addsym(namidx, SegData[UDATA]->SDoffset, size*count,
                    (s->ty() & mTYthread) ? STT_TLS : STT_OBJECT,
                    STB_WEAK, SHN_BSS);
    //dbg_printf("\tObj::common_block returning symidx %d\n",symidx);
    s->Sseg = UDATA;
    s->Sfl = FLudata;
    SegData[UDATA]->SDoffset += size * count;
    return symidx;
#endif
}

int Obj::common_block(Symbol *s, int flag, targ_size_t size, targ_size_t count)
{
    return Obj::common_block(s, size, count);
}

/***************************************
 * Append an iterated data block of 0s.
 * (uninitialized data only)
 */

void Obj::write_zeros(seg_data *pseg, targ_size_t count)
{
    Obj::lidata(pseg->SDseg, pseg->SDoffset, count);
}

/***************************************
 * Output an iterated data block of 0s.
 *
 *      For boundary alignment and initialization
 */

void Obj::lidata(int seg,targ_size_t offset,targ_size_t count)
{
    //printf("Obj::lidata(%d,%x,%d)\n",seg,offset,count);
    if (seg == UDATA || seg == UNKNOWN)
    {   // Use SDoffset to record size of .BSS section
        SegData[UDATA]->SDoffset += count;
    }
    else if (MAP_SEG2SEC(seg)->sh_type == SHT_NOBITS)
    {   // Use SDoffset to record size of .TBSS section
        SegData[seg]->SDoffset += count;
    }
    else
    {
        Obj::bytes(seg, offset, count, NULL);
    }
}

/***********************************
 * Append byte to segment.
 */

void Obj::write_byte(seg_data *pseg, unsigned byte)
{
    Obj::_byte(pseg->SDseg, pseg->SDoffset, byte);
}

/************************************
 * Output byte to object file.
 */

void Obj::_byte(int seg,targ_size_t offset,unsigned byte)
{
    Outbuffer *buf = SegData[seg]->SDbuf;
    int save = buf->size();
    //dbg_printf("Obj::_byte(seg=%d, offset=x%lx, byte=x%x)\n",seg,offset,byte);
    buf->setsize(offset);
    buf->writeByte(byte);
    if (save > offset+1)
        buf->setsize(save);
    else
        SegData[seg]->SDoffset = offset+1;
    //dbg_printf("\tsize now %d\n",buf->size());
}

/***********************************
 * Append bytes to segment.
 */

void Obj::write_bytes(seg_data *pseg, unsigned nbytes, void *p)
{
    Obj::bytes(pseg->SDseg, pseg->SDoffset, nbytes, p);
}

/************************************
 * Output bytes to object file.
 * Returns:
 *      nbytes
 */

unsigned Obj::bytes(int seg, targ_size_t offset, unsigned nbytes, void *p)
{
#if 0
    if (!(seg >= 0 && seg <= seg_count))
    {   printf("Obj::bytes: seg = %d, seg_count = %d\n", seg, seg_count);
        *(char*)0=0;
    }
#endif
    assert(seg >= 0 && seg <= seg_count);
    Outbuffer *buf = SegData[seg]->SDbuf;
    if (buf == NULL)
    {
        //dbg_printf("Obj::bytes(seg=%d, offset=x%lx, nbytes=%d, p=x%x)\n", seg, offset, nbytes, p);
        //raise(SIGSEGV);
        assert(buf != NULL);
    }
    int save = buf->size();
    //dbg_printf("Obj::bytes(seg=%d, offset=x%lx, nbytes=%d, p=x%x)\n",
            //seg,offset,nbytes,p);
    buf->position(offset, nbytes);
    if (p)
    {
        buf->writen(p,nbytes);
    }
    else
    {   // Zero out the bytes
        buf->clearn(nbytes);
    }
    if (save > offset+nbytes)
        buf->setsize(save);
    else
        SegData[seg]->SDoffset = offset+nbytes;
    return nbytes;
}

/*******************************
 * Output a relocation entry for a segment
 * Input:
 *      seg =           where the address is going
 *      offset =        offset within seg
 *      type =          ELF relocation type R_ARCH_XXXX
 *      index =         Related symbol table index
 *      val =           addend or displacement from address
 */

int relcnt=0;

void ElfObj::addrel(int seg, targ_size_t offset, unsigned type,
                    IDXSYM symidx, targ_size_t val)
{
    seg_data *segdata;
    Outbuffer *buf;
    IDXSEC secidx;

    //assert(val == 0);
    relcnt++;
    //dbg_printf("%d-ElfObj::addrel(seg %d,offset x%x,type x%x,symidx %d,val %d)\n",
            //relcnt,seg, offset, type, symidx,val);

    assert(seg >= 0 && seg <= seg_count);
    segdata = SegData[seg];
    secidx = MAP_SEG2SECIDX(seg);
    assert(secidx != 0);

    if (segdata->SDrel == NULL)
        segdata->SDrel = new Outbuffer();
    if (segdata->SDrel->size() == 0)
    {   IDXSEC relidx;

        if (secidx == SHN_TEXT)
            relidx = SHN_RELTEXT;
        else if (secidx == SHN_DATA)
            relidx = SHN_RELDATA;
        else
        {
            // Get the section name, and make a copy because
            // elf_newsection() may reallocate the string buffer.
            char *section_name = (char *)GET_SECTION_NAME(secidx);
            int len = strlen(section_name) + 1;
            char *p = (char *)alloca(len);
            memcpy(p, section_name, len);

            relidx = elf_newsection(I64 ? ".rela" : ".rel", p, I64 ? SHT_RELA : SHT_REL, 0);
            segdata->SDrelidx = relidx;
            addSectionToComdat(relidx,seg);
        }

        if (I64)
        {
            /* Note that we're using Elf32_Shdr here instead of Elf64_Shdr. This is to make
             * the code a bit simpler. In Obj::term(), we translate the Elf32_Shdr into the proper
             * Elf64_Shdr.
             */
            Elf32_Shdr *relsec = &SecHdrTab[relidx];
            relsec->sh_link = SHN_SYMTAB;
            relsec->sh_info = secidx;
            relsec->sh_entsize = sizeof(Elf64_Rela);
            relsec->sh_addralign = 8;
        }
        else
        {
            Elf32_Shdr *relsec = &SecHdrTab[relidx];
            relsec->sh_link = SHN_SYMTAB;
            relsec->sh_info = secidx;
            relsec->sh_entsize = sizeof(Elf32_Rel);
            relsec->sh_addralign = 4;
        }
    }

    if (I64)
    {
        Elf64_Rela rel;
        rel.r_offset = offset;          // build relocation information
        rel.r_info = ELF64_R_INFO(symidx,type);
        rel.r_addend = val;
        buf = segdata->SDrel;
        buf->write(&rel,sizeof(rel));
        segdata->SDrelcnt++;

        if (offset >= segdata->SDrelmaxoff)
            segdata->SDrelmaxoff = offset;
        else
        {   // insert numerically
            Elf64_Rela *relbuf = (Elf64_Rela *)buf->buf;
            int i = relbuf[segdata->SDrelindex].r_offset > offset ? 0 : segdata->SDrelindex;
            while (i < segdata->SDrelcnt)
            {
                if (relbuf[i].r_offset > offset)
                    break;
                i++;
            }
            assert(i != segdata->SDrelcnt);     // slide greater offsets down
            memmove(relbuf+i+1,relbuf+i,sizeof(Elf64_Rela) * (segdata->SDrelcnt - i - 1));
            *(relbuf+i) = rel;          // copy to correct location
            segdata->SDrelindex = i;    // next entry usually greater
        }
    }
    else
    {
        Elf32_Rel rel;
        rel.r_offset = offset;          // build relocation information
        rel.r_info = ELF32_R_INFO(symidx,type);
        buf = segdata->SDrel;
        buf->write(&rel,sizeof(rel));
        segdata->SDrelcnt++;

        if (offset >= segdata->SDrelmaxoff)
            segdata->SDrelmaxoff = offset;
        else
        {   // insert numerically
            Elf32_Rel *relbuf = (Elf32_Rel *)buf->buf;
            int i = relbuf[segdata->SDrelindex].r_offset > offset ? 0 : segdata->SDrelindex;
            while (i < segdata->SDrelcnt)
            {
                if (relbuf[i].r_offset > offset)
                    break;
                i++;
            }
            assert(i != segdata->SDrelcnt);     // slide greater offsets down
            memmove(relbuf+i+1,relbuf+i,sizeof(Elf32_Rel) * (segdata->SDrelcnt - i - 1));
            *(relbuf+i) = rel;          // copy to correct location
            segdata->SDrelindex = i;    // next entry usually greater
        }
    }
}

static size_t relsize64(unsigned type)
{
    assert(I64);
    switch (type)
    {
    case R_X86_64_NONE: return 0;
    case R_X86_64_64: return 8;
    case R_X86_64_PC32: return 4;
    case R_X86_64_GOT32: return 4;
    case R_X86_64_PLT32: return 4;
    case R_X86_64_COPY: return 0;
    case R_X86_64_GLOB_DAT: return 8;
    case R_X86_64_JUMP_SLOT: return 8;
    case R_X86_64_RELATIVE: return 8;
    case R_X86_64_GOTPCREL: return 4;
    case R_X86_64_32: return 4;
    case R_X86_64_32S: return 4;
    case R_X86_64_16: return 2;
    case R_X86_64_PC16: return 2;
    case R_X86_64_8: return 1;
    case R_X86_64_PC8: return 1;
    case R_X86_64_DTPMOD64: return 8;
    case R_X86_64_DTPOFF64: return 8;
    case R_X86_64_TPOFF64: return 8;
    case R_X86_64_TLSGD: return 4;
    case R_X86_64_TLSLD: return 4;
    case R_X86_64_DTPOFF32: return 4;
    case R_X86_64_GOTTPOFF: return 4;
    case R_X86_64_TPOFF32: return 4;
    case R_X86_64_PC64: return 8;
    case R_X86_64_GOTOFF64: return 8;
    case R_X86_64_GOTPC32: return 4;
    default:
        break;
    }
    assert(0);
    return 0;
}

static size_t relsize32(unsigned type)
{
    assert(I32);
    switch (type)
    {
    case R_386_NONE: return 0;
    case R_386_32: return 4;
    case R_386_PC32: return 4;
    case R_386_GOT32: return 4;
    case R_386_PLT32: return 4;
    case R_386_COPY: return 0;
    case R_386_GLOB_DAT: return 4;
    case R_386_JMP_SLOT: return 4;
    case R_386_RELATIVE: return 4;
    case R_386_GOTOFF: return 4;
    case R_386_GOTPC: return 4;
    case R_386_TLS_TPOFF: return 4;
    case R_386_TLS_IE: return 4;
    case R_386_TLS_GOTIE: return 4;
    case R_386_TLS_LE: return 4;
    case R_386_TLS_GD: return 4;
    case R_386_TLS_LDM: return 4;
    case R_386_TLS_GD_32: return 4;
    case R_386_TLS_GD_PUSH: return 4;
    case R_386_TLS_GD_CALL: return 4;
    case R_386_TLS_GD_POP: return 4;
    case R_386_TLS_LDM_32: return 4;
    case R_386_TLS_LDM_PUSH: return 4;
    case R_386_TLS_LDM_CALL: return 4;
    case R_386_TLS_LDM_POP: return 4;
    case R_386_TLS_LDO_32: return 4;
    case R_386_TLS_IE_32: return 4;
    case R_386_TLS_LE_32: return 4;
    case R_386_TLS_DTPMOD32: return 4;
    case R_386_TLS_DTPOFF32: return 4;
    case R_386_TLS_TPOFF32: return 4;
    default:
        break;
    }
    assert(0);
    return 0;
}

/*******************************
 * Write/Append a value to the given segment and offset.
 *      targseg =       the target segment for the relocation
 *      offset =        offset within target segment
 *      val =           addend or displacement from symbol
 *      size =          number of bytes to write
 */
static size_t writeaddrval(int targseg, size_t offset, targ_size_t val, size_t size)
{
    assert(targseg >= 0 && targseg <= seg_count);

    Outbuffer *buf = SegData[targseg]->SDbuf;
    const size_t save = buf->size();
    buf->setsize(offset);
    buf->write(&val, size);
    // restore Outbuffer position
    if (save > offset + size)
        buf->setsize(save);
    return size;
}

/*******************************
 * Write/Append a relocatable value to the given segment and offset.
 * Input:
 *      targseg =       the target segment for the relocation
 *      offset =        offset within target segment
 *      reltype =       ELF relocation type R_ARCH_XXXX
 *      symidx =        symbol base for relocation
 *      val =           addend or displacement from symbol
 */
size_t ElfObj::writerel(int targseg, size_t offset, unsigned reltype,
                        IDXSYM symidx, targ_size_t val)
{
    assert(reltype != R_X86_64_NONE);

    size_t sz;
    if (I64)
    {
        // Elf64_Rela stores addend in Rela.r_addend field
        sz = relsize64(reltype);
        writeaddrval(targseg, offset, 0, sz);
        addrel(targseg, offset, reltype, symidx, val);
    }
    else
    {
        assert(I32);
        // Elf32_Rel stores addend in target location
        sz = relsize32(reltype);
        writeaddrval(targseg, offset, val, sz);
        addrel(targseg, offset, reltype, symidx, 0);
    }
    return sz;
}

/*******************************
 * Refer to address that is in the data segment.
 * Input:
 *      seg =           where the address is going
 *      offset =        offset within seg
 *      val =           displacement from address
 *      targetdatum =   DATA, CDATA or UDATA, depending where the address is
 *      flags =         CFoff, CFseg, CFoffset64, CFswitch
 * Example:
 *      int *abc = &def[3];
 *      to allocate storage:
 *              Obj::reftodatseg(DATA,offset,3 * sizeof(int *),UDATA);
 * Note:
 *      For I64 && (flags & CFoffset64) && (flags & CFswitch)
 *      targetdatum is a symidx rather than a segment.
 */

void Obj::reftodatseg(int seg,targ_size_t offset,targ_size_t val,
        unsigned targetdatum,int flags)
{
#if 0
    printf("Obj::reftodatseg(seg=%d, offset=x%llx, val=x%llx,data %x, flags %x)\n",
        seg,(unsigned long long)offset,(unsigned long long)val,targetdatum,flags);
#endif
    int relinfo;
    IDXSYM targetsymidx = STI_RODAT;
    if (I64)
    {

        if (flags & CFoffset64)
        {
            relinfo = R_X86_64_64;
            if (flags & CFswitch) targetsymidx = targetdatum;
        }
        else if (flags & CFswitch)
        {
            relinfo = R_X86_64_PC32;
            targetsymidx = MAP_SEG2SYMIDX(targetdatum);
        }
        else if (MAP_SEG2TYP(seg) == CODE && config.flags3 & CFG3pic)
        {
            relinfo = R_X86_64_PC32;
            val -= 4;
            targetsymidx = MAP_SEG2SYMIDX(targetdatum);
        }
        else if (MAP_SEG2SEC(targetdatum)->sh_flags & SHF_TLS)
            relinfo = config.flags3 & CFG3pic ? R_X86_64_TLSGD : R_X86_64_TPOFF32;
        else
        {
            relinfo = targetdatum == CDATA ? R_X86_64_32 : R_X86_64_32S;
            targetsymidx = MAP_SEG2SYMIDX(targetdatum);
        }
    }
    else
    {
        if (MAP_SEG2TYP(seg) == CODE && config.flags3 & CFG3pic)
            relinfo = R_386_GOTOFF;
        else if (MAP_SEG2SEC(targetdatum)->sh_flags & SHF_TLS)
            relinfo = config.flags3 & CFG3pic ? R_386_TLS_GD : R_386_TLS_LE;
        else
            relinfo = R_386_32;
        targetsymidx = MAP_SEG2SYMIDX(targetdatum);
    }
    ElfObj::writerel(seg, offset, relinfo, targetsymidx, val);
}

/*******************************
 * Refer to address that is in the code segment.
 * Only offsets are output, regardless of the memory model.
 * Used to put values in switch address tables.
 * Input:
 *      seg =           where the address is going (CODE or DATA)
 *      offset =        offset within seg
 *      val =           displacement from start of this module
 */

void Obj::reftocodeseg(int seg,targ_size_t offset,targ_size_t val)
{
    //dbg_printf("Obj::reftocodeseg(seg=%d, offset=x%lx, val=x%lx )\n",seg,offset,val);

    int relinfo;
#if 0
    if (MAP_SEG2TYP(seg) == CODE)
    {
        relinfo = RI_TYPE_PC32;
    }
    else
#endif
    {
        if (I64)
            relinfo = (config.flags3 & CFG3pic) ? R_X86_64_PC32 : R_X86_64_32;
        else
            relinfo = (config.flags3 & CFG3pic) ? R_386_GOTOFF : R_386_32;
    }
    ElfObj::writerel(seg, offset, relinfo, funcsym_p->Sxtrnnum, val - funcsym_p->Soffset);
}

/*******************************
 * Refer to an identifier.
 * Input:
 *      segtyp =        where the address is going (CODE or DATA)
 *      offset =        offset within seg
 *      s ->            Symbol table entry for identifier
 *      val =           displacement from identifier
 *      flags =         CFselfrel: self-relative
 *                      CFseg: get segment
 *                      CFoff: get offset
 *                      CFoffset64: 64 bit fixup
 *                      CFpc32: I64: PC relative 32 bit fixup
 * Returns:
 *      number of bytes in reference (4 or 8)
 */

int Obj::reftoident(int seg, targ_size_t offset, Symbol *s, targ_size_t val,
        int flags)
{
    bool external = TRUE;
    Outbuffer *buf;
    Elf32_Word relinfo=R_X86_64_NONE,refseg;
    int segtyp = MAP_SEG2TYP(seg);
    //assert(val == 0);
    int retsize = (flags & CFoffset64) ? 8 : 4;

#if 0
    printf("\nObj::reftoident('%s' seg %d, offset x%llx, val x%llx, flags x%x)\n",
        s->Sident,seg,offset,val,flags);
    dbg_printf("Sseg = %d, Sxtrnnum = %d, retsize = %d\n",s->Sseg,s->Sxtrnnum,retsize);
    symbol_print(s);
#endif

    tym_t ty = s->ty();
    if (s->Sxtrnnum)
    {                           // identifier is defined somewhere else
        if (I64)
        {
            if (SymbolTable64[s->Sxtrnnum].st_shndx != SHN_UNDEF)
                external = FALSE;
        }
        else
        {
            if (SymbolTable[s->Sxtrnnum].st_shndx != SHN_UNDEF)
                external = FALSE;
        }
    }

    switch (s->Sclass)
    {
        case SClocstat:
            if (I64)
            {
                if (s->Sfl == FLtlsdata)
                    relinfo = config.flags3 & CFG3pic ? R_X86_64_TLSGD : R_X86_64_TPOFF32;
                else
                {   relinfo = config.flags3 & CFG3pic ? R_X86_64_PC32 : R_X86_64_32;
                    if (flags & CFpc32)
                        relinfo = R_X86_64_PC32;
                }
            }
            else
            {
                if (s->Sfl == FLtlsdata)
                    relinfo = config.flags3 & CFG3pic ? R_386_TLS_GD : R_386_TLS_LE;
                else
                    relinfo = config.flags3 & CFG3pic ? R_386_GOTOFF : R_386_32;
            }
            if (flags & CFoffset64 && relinfo == R_X86_64_32)
            {
                relinfo = R_X86_64_64;
                retsize = 8;
            }
            refseg = STI_RODAT;
            val += s->Soffset;
            goto outrel;

        case SCcomdat:
        case_SCcomdat:
        case SCstatic:
#if 0
            if ((s->Sflags & SFLthunk) && s->Soffset)
            {                   // A thunk symbol that has be defined
                assert(s->Sseg == seg);
                val = (s->Soffset+val) - (offset+4);
                goto outaddrval;
            }
            // FALL_THROUGH
#endif

        case SCextern:
        case SCcomdef:
        case_extern:
        case SCglobal:
            if (!s->Sxtrnnum)
            {   // not in symbol table yet - class might change
                //printf("\tadding %s to fixlist\n",s->Sident);
                size_t numbyteswritten = addtofixlist(s,offset,seg,val,flags);
                assert(numbyteswritten == retsize);
                return retsize;
            }
            else
            {
                refseg = s->Sxtrnnum;       // default to name symbol table entry

                if (flags & CFselfrel)
                {               // only for function references within code segments
                    if (!external &&            // local definition found
                         s->Sseg == seg &&      // within same code segment
                          (!(config.flags3 & CFG3pic) ||        // not position indp code
                           s->Sclass == SCstatic)) // or is pic, but declared static
                    {                   // Can use PC relative
                        //dbg_printf("\tdoing PC relative\n");
                        val = (s->Soffset+val) - (offset+4);
                    }
                    else
                    {
                        //dbg_printf("\tadding relocation\n");
                        if (I64)
                            relinfo = config.flags3 & CFG3pic ?  R_X86_64_PLT32 : R_X86_64_PC32;
                        else
                            relinfo = config.flags3 & CFG3pic ?  R_386_PLT32 : R_386_PC32;
                        val = (targ_size_t)-4;
                    }
                }
                else
                {       // code to code code to data, data to code, data to data refs
                    if (s->Sclass == SCstatic)
                    {                           // offset into .data or .bss seg
                        refseg = MAP_SEG2SYMIDX(s->Sseg);
                                                // use segment symbol table entry
                        val += s->Soffset;
                        if (!(config.flags3 & CFG3pic) ||       // all static refs from normal code
                             segtyp == DATA)    // or refs from data from posi indp
                        {
                            if (I64)
                                relinfo = (flags & CFpc32) ? R_X86_64_PC32 : R_X86_64_32;
                            else
                                relinfo = R_386_32;
                        }
                        else
                        {
                            relinfo = I64 ? R_X86_64_PC32 : R_386_GOTOFF;
                        }
                    }
                    else if (config.flags3 & CFG3pic && s == GOTsym)
                    {                   // relocation for Gbl Offset Tab
                        relinfo =  I64 ? R_X86_64_NONE : R_386_GOTPC;
                    }
                    else if (segtyp == DATA)
                    {                   // relocation from within DATA seg
                        relinfo = I64 ? R_X86_64_32 : R_386_32;
                        if (I64 && flags & CFpc32)
                            relinfo = R_X86_64_PC32;
                    }
                    else
                    {                   // relocation from within CODE seg
                        if (I64)
                        {   if (config.flags3 & CFG3pic)
                                relinfo = R_X86_64_GOTPCREL;
                            else
                                relinfo = (flags & CFpc32) ? R_X86_64_PC32 : R_X86_64_32;
                        }
                        else
                            relinfo = config.flags3 & CFG3pic ? R_386_GOT32 : R_386_32;
                    }
                    if ((s->ty() & mTYLINK) & mTYthread)
                    {
                        if (I64)
                        {
                            if (config.flags3 & CFG3pic)
                            {
                                if (s->Sclass == SCstatic || s->Sclass == SClocstat)
                                    // Could use 'local dynamic (LD)' to optimize multiple local TLS reads
                                    relinfo = R_X86_64_TLSGD;
                                else
                                    relinfo = R_X86_64_TLSGD;
                            }
                            else
                            {
                                if (s->Sclass == SCstatic || s->Sclass == SClocstat)
                                    relinfo = R_X86_64_TPOFF32;
                                else
                                    relinfo = R_X86_64_GOTTPOFF;
                            }
                        }
                        else
                        {
                            if (config.flags3 & CFG3pic)
                            {
                                if (s->Sclass == SCstatic)
                                    // Could use 'local dynamic (LD)' to optimize multiple local TLS reads
                                    relinfo = R_386_TLS_GD;
                                else
                                    relinfo = R_386_TLS_GD;
                            }
                            else
                            {
                                if (s->Sclass == SCstatic)
                                    relinfo = R_386_TLS_LE;
                                else
                                    relinfo = R_386_TLS_IE;
                            }
                        }
                    }
                    if (flags & CFoffset64 && relinfo == R_X86_64_32)
                    {
                        relinfo = R_X86_64_64;
                    }
                }
                if (relinfo == R_X86_64_NONE)
                {
                outaddrval:
                    writeaddrval(seg, offset, val, retsize);
                }
                else
                {
                outrel:
                    //printf("\t\t************* adding relocation\n");
                    const size_t nbytes = ElfObj::writerel(seg, offset, relinfo, refseg, val);
                    assert(nbytes == retsize);
                }
            }
            break;

        case SCsinline:
        case SCeinline:
            printf ("Undefined inline value <<fixme>>\n");
            //warerr(WM_undefined_inline,s->Sident);
        case SCinline:
            if (tyfunc(ty))
            {
                s->Sclass = SCextern;
                goto case_extern;
            }
            else if (config.flags2 & CFG2comdat)
                goto case_SCcomdat;     // treat as initialized common block

        default:
            //symbol_print(s);
            assert(0);
    }
    return retsize;
}

/*****************************************
 * Generate far16 thunk.
 * Input:
 *      s       Symbol to generate a thunk for
 */

void Obj::far16thunk(Symbol *s)
{
    //dbg_printf("Obj::far16thunk('%s')\n", s->Sident);
    assert(0);
}

/**************************************
 * Mark object file as using floating point.
 */

void Obj::fltused()
{
    //dbg_printf("Obj::fltused()\n");
}

/************************************
 * Close and delete .OBJ file.
 */

void objfile_delete()
{
    //remove(fobjname); // delete corrupt output file
}

/**********************************
 * Terminate.
 */

void objfile_term()
{
#if TERMCODE
    mem_free(fobjname);
    fobjname = NULL;
#endif
}

/**********************************
  * Write to the object file
  */
void objfile_write(FILE *fd, void *buffer, unsigned len)
{
    fobjbuf->write(buffer, len);
}

long elf_align(targ_size_t size,long foffset)
{
    if (size <= 1)
        return foffset;
    long offset = (foffset + size - 1) & ~(size - 1);
    if (offset > foffset)
        fobjbuf->writezeros(offset - foffset);
    return offset;
}

/***************************************
 * Stuff pointer to ModuleInfo into its own section (minfo).
 */

#if MARS

void Obj::moduleinfo(Symbol *scc)
{
    const int CFflags = I64 ? (CFoffset64 | CFoff) : CFoff;

    // needs to be writeable for PIC code, see Bugzilla 13117
    const int shf_flags = SHF_ALLOC | SHF_WRITE;
    const int seg = ElfObj::getsegment("minfo", NULL, SHT_PROGBITS, shf_flags, NPTRSIZE);
    SegData[seg]->SDoffset +=
        reftoident(seg, SegData[seg]->SDoffset, scc, 0, CFflags);
}


/***************************************
 * Create startup/shutdown code to register an executable/shared
 * library (DSO) with druntime. Create one for each object file and
 * put the sections into a COMDAT group. This will ensure that each
 * DSO gets registered only once.
 */

static void obj_rtinit()
{
#if TX86
    // section start/stop symbols are defined by the linker (http://www.airs.com/blog/archives/56)
    // make the symbols hidden so that each DSO gets it's own brackets
    IDXSYM minfo_beg, minfo_end, dso_rec;
    IDXSTR namidx;
    int seg;

    {
    // needs to be writeable for PIC code, see Bugzilla 13117
    const int shf_flags = SHF_ALLOC | SHF_WRITE;

    namidx = Obj::addstr(symtab_strings,"__start_minfo");
    minfo_beg = elf_addsym(namidx, 0, 0, STT_NOTYPE, STB_GLOBAL, SHN_UNDEF, STV_HIDDEN);

    ElfObj::getsegment("minfo", NULL, SHT_PROGBITS, shf_flags, NPTRSIZE);

    namidx = Obj::addstr(symtab_strings,"__stop_minfo");
    minfo_end = elf_addsym(namidx, 0, 0, STT_NOTYPE, STB_GLOBAL, SHN_UNDEF, STV_HIDDEN);
    }

    // Create a COMDAT section group
    const int groupseg = ElfObj::getsegment(".group.d_dso", NULL, SHT_GROUP, 0, 0);
    SegData[groupseg]->SDbuf->write32(GRP_COMDAT);

    {
        /*
         * Create an instance of DSORec as global static data in the section .data.d_dso_rec
         * It is writeable and allows the runtime to store information.
         * Make it a COMDAT so there's only one per DSO.
         *
         * typedef union
         * {
         *     size_t        id;
         *     void       *data;
         * } DSORec;
         */
        seg = ElfObj::getsegment(".data.d_dso_rec", NULL, SHT_PROGBITS,
                         SHF_ALLOC|SHF_WRITE|SHF_GROUP, NPTRSIZE);
        dso_rec = MAP_SEG2SYMIDX(seg);
        Obj::bytes(seg, 0, NPTRSIZE, NULL);
        // add to section group
        SegData[groupseg]->SDbuf->write32(MAP_SEG2SECIDX(seg));

        /*
         * Create an instance of DSO on the stack:
         *
         * typedef struct
         * {
         *     size_t                version;
         *     DSORec               *dso_rec;
         *     void   *minfo_beg, *minfo_end;
         * } DSO;
         *
         * Generate the following function as a COMDAT so there's only one per DSO:
         *  .text.d_dso_init    segment
         *      push    EBP
         *      mov     EBP,ESP
         *      sub     ESP,align
         *      lea     RAX,minfo_end[RIP]
         *      push    RAX
         *      lea     RAX,minfo_beg[RIP]
         *      push    RAX
         *      lea     RAX,.data.d_dso_rec[RIP]
         *      push    RAX
         *      push    1       // version
         *      mov     RDI,RSP
         *      call      _d_dso_registry@PLT32
         *      leave
         *      ret
         * and then put a pointer to that function in .ctors and in .dtors so it'll
         * get executed once upon loading and once upon unloading the DSO.
         */
        int codseg;
        {
            codseg = ElfObj::getsegment(".text.d_dso_init", NULL, SHT_PROGBITS,
                                    SHF_ALLOC|SHF_EXECINSTR|SHF_GROUP, NPTRSIZE);
            // add to section group
            SegData[groupseg]->SDbuf->write32(MAP_SEG2SECIDX(codseg));

#if DEBUG
            // adds a local symbol (name) to the code, useful to set a breakpoint
            namidx = ElfObj::addstr(symtab_strings, "__d_dso_init");
            elf_addsym(namidx, 0, 0, STT_FUNC, STB_LOCAL, MAP_SEG2SECIDX(codseg));
#endif
        }
        Outbuffer *buf = SegData[codseg]->SDbuf;
        assert(!buf->size());
        size_t off = 0;

        // 16-byte align for call
        const size_t sizeof_dso = 6 * NPTRSIZE;
        const size_t align = I64 ?
            // return address, RBP, DSO
            (-(2 * NPTRSIZE + sizeof_dso) & 0xF) :
            // return address, EBP, EBX, DSO, arg
            (-(3 * NPTRSIZE + sizeof_dso + NPTRSIZE) & 0xF);

        // push EBP
        buf->writeByte(0x50 + BP);
        off += 1;
        // mov EBP, ESP
        if (I64)
        {
            buf->writeByte(REX | REX_W);
            off += 1;
        }
        buf->writeByte(0x8B);
        buf->writeByte(modregrm(3,BP,SP));
        off += 2;
        // sub ESP, align
        if (align)
        {
            if (I64)
            {
                buf->writeByte(REX | REX_W);
                off += 1;
            }
            buf->writeByte(0x81);
            buf->writeByte(modregrm(3,5,SP));
            buf->writeByte(align & 0xFF);
            buf->writeByte(align >> 8 & 0xFF);
            buf->writeByte(0);
            buf->writeByte(0);
            off += 6;
        }

        if (config.flags3 & CFG3pic && I32)
        {   // see cod3_load_got() for reference
            // push EBX
            buf->writeByte(0x50 + BX);
            off += 1;
            // call L1
            buf->writeByte(0xE8);
            buf->write32(0);
            // L1: pop EBX (now contains EIP)
            buf->writeByte(0x58 + BX);
            off += 6;
            // add EBX,_GLOBAL_OFFSET_TABLE_+3
            buf->writeByte(0x81);
            buf->writeByte(modregrm(3,0,BX));
            off += 2;
            off += ElfObj::writerel(codseg, off, R_386_GOTPC, Obj::external(Obj::getGOTsym()), 3);
        }

        int reltype;
        if (config.flags3 & CFG3pic)
            reltype = I64 ? R_X86_64_PC32 : R_386_GOTOFF;
        else
            reltype = I64 ? R_X86_64_32 : R_386_32;

        const IDXSYM syms[] = {dso_rec, minfo_beg, minfo_end};

        for (size_t i = sizeof(syms) / sizeof(syms[0]); i--; )
        {
            const IDXSYM sym = syms[i];

            if (config.flags3 & CFG3pic)
            {
                if (I64)
                {
                    // lea RAX, sym[RIP]
                    buf->writeByte(REX | REX_W);
                    buf->writeByte(0x8D);
                    buf->writeByte(modregrm(0,AX,5));
                    off += 3;
                    off += ElfObj::writerel(codseg, off, reltype, syms[i], -4);
                }
                else
                {
                    // lea EAX, sym[EBX]
                    buf->writeByte(0x8D);
                    buf->writeByte(modregrm(2,AX,BX));
                    off += 2;
                    off += ElfObj::writerel(codseg, off, reltype, syms[i], 0);
                }
            }
            else
            {
                // mov EAX, sym
                buf->writeByte(0xB8 + AX);
                off += 1;
                off += ElfObj::writerel(codseg, off, reltype, syms[i], 0);
            }
            // push RAX
            buf->writeByte(0x50 + AX);
            off += 1;
        }
        // Pass a version flag to simplify future extensions.
        static const size_t ver = 1;
        // push imm8
        assert(!(ver & ~0xFF));
        buf->writeByte(0x6A);
        buf->writeByte(ver);
        off += 2;

        if (I64)
        {   // mov RDI, DSO*
            buf->writeByte(REX | REX_W);
            buf->writeByte(0x8B);
            buf->writeByte(modregrm(3,DI,SP));
            off += 3;
        }
        else
        {   // push DSO*
            buf->writeByte(0x50 + SP);
            off += 1;
        }

#if REQUIRE_DSO_REGISTRY

        const IDXSYM symidx = Obj::external_def("_d_dso_registry");

        // call _d_dso_registry@PLT
        buf->writeByte(0xE8);
        off += 1;
        off += ElfObj::writerel(codseg, off, I64 ? R_X86_64_PLT32 : R_386_PLT32, symidx, -4);

#else

        // use a weak reference for _d_dso_registry
        namidx = ElfObj::addstr(symtab_strings, "_d_dso_registry");
        const IDXSYM symidx = elf_addsym(namidx, 0, 0, STT_NOTYPE, STB_WEAK, SHN_UNDEF);

        if (config.flags3 & CFG3pic)
        {
            if (I64)
            {
                // cmp foo@GOT[RIP], 0
                buf->writeByte(REX | REX_W);
                buf->writeByte(0x83);
                buf->writeByte(modregrm(0,7,5));
                off += 3;
                off += ElfObj::writerel(codseg, off, R_X86_64_GOTPCREL, symidx, -5);
                buf->writeByte(0);
                off += 1;
            }
            else
            {
                // cmp foo[GOT], 0
                buf->writeByte(0x81);
                buf->writeByte(modregrm(2,7,BX));
                off += 2;
                off += ElfObj::writerel(codseg, off, R_386_GOT32, symidx, 0);
                buf->write32(0);
                off += 4;
            }
            // jz +5
            buf->writeByte(0x74);
            buf->writeByte(0x05);
            off += 2;

            // call foo@PLT[RIP]
            buf->writeByte(0xE8);
            off += 1;
            off += ElfObj::writerel(codseg, off, I64 ? R_X86_64_PLT32 : R_386_PLT32, symidx, -4);
        }
        else
        {
            // mov ECX, offset foo
            buf->writeByte(0xB8 + CX);
            off += 1;
            reltype = I64 ? R_X86_64_32 : R_386_32;
            off += ElfObj::writerel(codseg, off, reltype, symidx, 0);

            // test ECX, ECX
            buf->writeByte(0x85);
            buf->writeByte(modregrm(3,CX,CX));

            // jz +5 (skip call)
            buf->writeByte(0x74);
            buf->writeByte(0x05);
            off += 4;

            // call _d_dso_registry[RIP]
            buf->writeByte(0xE8);
            off += 1;
            off += ElfObj::writerel(codseg, off, I64 ? R_X86_64_PC32 : R_386_PC32, symidx, -4);
        }

#endif // REQUIRE_DSO_REGISTRY

        if (config.flags3 & CFG3pic && I32)
        {   // mov EBX,[EBP-4-align]
            buf->writeByte(0x8B);
            buf->writeByte(modregrm(1,BX,BP));
            buf->writeByte(-4-align);
            off += 3;
        }
        // leave
        buf->writeByte(0xC9);
        // ret
        buf->writeByte(0xC3);
        off += 2;
        Offset(codseg) = off;

        // put a reference into .ctors/.dtors each
        const char *p[] = {".dtors.d_dso_dtor", ".ctors.d_dso_ctor"};
        // needs to be writeable for PIC code, see Bugzilla 13117
        const int flags = SHF_ALLOC | SHF_WRITE | SHF_GROUP;
        for (size_t i = 0; i < 2; ++i)
        {
            seg = ElfObj::getsegment(p[i], NULL, SHT_PROGBITS, flags, NPTRSIZE);
            assert(!SegData[seg]->SDbuf->size());

            // add to section group
            SegData[groupseg]->SDbuf->write32(MAP_SEG2SECIDX(seg));

            // relocation
            if (I64)
                reltype = R_X86_64_64;
            else
                reltype = R_386_32;

            SegData[seg]->SDoffset += ElfObj::writerel(seg, 0, reltype, MAP_SEG2SYMIDX(codseg), 0);
        }
    }
    // set group section infos
    Offset(groupseg) = SegData[groupseg]->SDbuf->size();
    Elf32_Shdr *p = MAP_SEG2SEC(groupseg);
    p->sh_link    = SHN_SYMTAB;
    p->sh_info    = dso_rec; // set the dso_rec as group symbol
    p->sh_entsize = sizeof(IDXSYM);
    p->sh_size    = Offset(groupseg);
#else
    assert(0);
#endif
}

#endif // MARS

/*************************************
 */

void Obj::gotref(symbol *s)
{
    //printf("Obj::gotref(%x '%s', %d)\n",s,s->Sident, s->Sclass);
    switch(s->Sclass)
    {
        case SCstatic:
        case SClocstat:
            s->Sfl = FLgotoff;
            break;

        case SCextern:
        case SCglobal:
        case SCcomdat:
        case SCcomdef:
            s->Sfl = FLgot;
            break;

        default:
            break;
    }
}

symbol *Obj::tlv_bootstrap()
{
    // specific for Mach-O
    assert(0);
    return NULL;
}

void Obj::write_pointerRef(Symbol* s, unsigned off)
{
}

/******************************************
 * Generate fixup specific to .eh_frame and .gcc_except_table sections.
 * Params:
 *      seg = segment of where to write fixup
 *      offset = offset of where to write fixup
 *      s = fixup is a reference to this Symbol
 *      val = displacement from s
 * Returns:
 *      number of bytes written at seg:offset
 */
int dwarf_reftoident(int seg, targ_size_t offset, Symbol *s, targ_size_t val)
{
    if (config.flags3 & CFG3pic)
    {
        /* fixup: R_X86_64_PC32 sym="DW.ref.name"
         * symtab: .weak DW.ref.name,@OBJECT,VALUE=.data.DW.ref.name+0x00,SIZE=8
         * Section 13  .data.DW.ref.name  PROGBITS,ALLOC,WRITE,SIZE=0x0008(8),OFFSET=0x0138,ALIGN=8
         *  0138:   0  0  0  0  0  0  0  0                           ........
         * Section 14  .rela.data.DW.ref.name  RELA,ENTRIES=1,OFFSET=0x0E18,ALIGN=8,LINK=22,INFO=13
         *   0 offset=00000000 addend=0000000000000000 type=R_X86_64_64 sym="name"
         */
        if (!s->Sdw_ref_idx)
        {
            int dataDWref_seg = ElfObj::getsegment(".data.DW.ref.", s->Sident, SHT_PROGBITS, SHF_ALLOC|SHF_WRITE, I64 ? 8 : 4);
            Outbuffer *buf = SegData[dataDWref_seg]->SDbuf;
            assert(buf->size() == 0);
            ElfObj::reftoident(dataDWref_seg, 0, s, 0, I64 ? CFoffset64 : CFoff);

            // Add "DW.ref." ~ name to the symtab_strings table
            IDXSTR namidx = symtab_strings->size();
            symtab_strings->writeString("DW.ref.");
            symtab_strings->setsize(symtab_strings->size() - 1);  // back up over terminating 0
            symtab_strings->writeString(s->Sident);

            s->Sdw_ref_idx = elf_addsym(namidx, val, 8, STT_OBJECT, STB_WEAK, MAP_SEG2SECIDX(dataDWref_seg), STV_HIDDEN);
        }
        ElfObj::writerel(seg, offset, I64 ? R_X86_64_PC32 : R_386_PC32, s->Sdw_ref_idx, 0);
    }
    else
    {
        ElfObj::reftoident(seg, offset, s, val, CFoff);
        //dwarf_addrel(seg, offset, s->Sseg, s->Soffset);
        //et->write32(s->Soffset);
    }
    return 4;
}

#endif

#endif