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reent.h
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reent.h
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/* This header file provides the reentrancy. */
/* The reentrant system calls here serve two purposes:
1) Provide reentrant versions of the system calls the ANSI C library
requires.
2) Provide these system calls in a namespace clean way.
It is intended that *all* system calls that the ANSI C library needs
be declared here. It documents them all in one place. All library access
to the system is via some form of these functions.
The target may provide the needed syscalls by any of the following:
1) Define the reentrant versions of the syscalls directly.
(eg: _open_r, _close_r, etc.). Please keep the namespace clean.
When you do this, set "syscall_dir" to "syscalls" and add
-DREENTRANT_SYSCALLS_PROVIDED to newlib_cflags in configure.host.
2) Define namespace clean versions of the system calls by prefixing
them with '_' (eg: _open, _close, etc.). Technically, there won't be
true reentrancy at the syscall level, but the library will be namespace
clean.
When you do this, set "syscall_dir" to "syscalls" in configure.host.
3) Define or otherwise provide the regular versions of the syscalls
(eg: open, close, etc.). The library won't be reentrant nor namespace
clean, but at least it will work.
When you do this, add -DMISSING_SYSCALL_NAMES to newlib_cflags in
configure.host.
4) Define or otherwise provide the regular versions of the syscalls,
and do not supply functional interfaces for any of the reentrant
calls. With this method, the reentrant syscalls are redefined to
directly call the regular system call without the reentrancy argument.
When you do this, specify both -DREENTRANT_SYSCALLS_PROVIDED and
-DMISSING_SYSCALL_NAMES via newlib_cflags in configure.host and do
not specify "syscall_dir".
Stubs of the reentrant versions of the syscalls exist in the libc/reent
source directory and are provided if REENTRANT_SYSCALLS_PROVIDED isn't
defined. These stubs call the native system calls: _open, _close, etc.
if MISSING_SYSCALL_NAMES is *not* defined, otherwise they call the
non-underscored versions: open, close, etc. when MISSING_SYSCALL_NAMES
*is* defined.
By default, newlib functions call the reentrant syscalls internally,
passing a reentrancy structure as an argument. This reentrancy structure
contains data that is thread-specific. For example, the errno value is
kept in the reentrancy structure. If multiple threads exist, each will
keep a separate errno value which is intuitive since the application flow
cannot check for failure reliably otherwise.
The reentrant syscalls are either provided by the platform, by the
libc/reent stubs, or in the case of both MISSING_SYSCALL_NAMES and
REENTRANT_SYSCALLS_PROVIDED being defined, the calls are redefined to
simply call the regular syscalls with no reentrancy struct argument.
A single-threaded application does not need to worry about the reentrancy
structure. It is used internally.
A multi-threaded application needs either to manually manage reentrancy
structures or use dynamic reentrancy.
Manually managing reentrancy structures entails calling special reentrant
versions of newlib functions that have an additional reentrancy argument.
For example, _printf_r. By convention, the first argument is the
reentrancy structure. By default, the normal version of the function
uses the default reentrancy structure: _REENT. The reentrancy structure
is passed internally, eventually to the reentrant syscalls themselves.
How the structures are stored and accessed in this model is up to the
application.
Dynamic reentrancy is specified by the __DYNAMIC_REENT__ flag. This
flag denotes setting up a macro to replace _REENT with a function call
to __getreent(). This function needs to be implemented by the platform
and it is meant to return the reentrancy structure for the current
thread. When the regular C functions (e.g. printf) go to call internal
routines with the default _REENT structure, they end up calling with
the reentrancy structure for the thread. Thus, application code does not
need to call the _r routines nor worry about reentrancy structures. */
/* WARNING: All identifiers here must begin with an underscore. This file is
included by stdio.h and others and we therefore must only use identifiers
in the namespace allotted to us. */
#ifndef _REENT_H_
#ifdef __cplusplus
extern "C" {
#endif
#define _REENT_H_
#include <sys/reent.h>
#include <sys/_types.h>
#define __need_size_t
#define __need_ptrdiff_t
#include <stddef.h>
/* FIXME: not namespace clean */
struct stat;
struct tms;
struct timeval;
struct timezone;
#if defined(REENTRANT_SYSCALLS_PROVIDED) && defined(MISSING_SYSCALL_NAMES)
#define _close_r(__reent, __fd) close(__fd)
#define _execve_r(__reent, __f, __arg, __env) execve(__f, __arg, __env)
#define _fcntl_r(__reent, __fd, __cmd, __arg) fcntl(__fd, __cmd, __arg)
#define _fork_r(__reent) fork()
#define _fstat_r(__reent, __fdes, __stat) fstat(__fdes, __stat)
#define _getpid_r(__reent) getpid()
#define _isatty_r(__reent, __desc) isatty(__desc)
#define _kill_r(__reent, __pid, __signal) kill(__pid, __signal)
#define _link_r(__reent, __oldpath, __newpath) link(__oldpath, __newpath)
#define _lseek_r(__reent, __fdes, __off, __w) lseek(__fdes, __off, __w)
#define _mkdir_r(__reent, __path, __m) mkdir(__path, __m)
#define _open_r(__reent, __path, __flag, __m) open(__path, __flag, __m)
#define _read_r(__reent, __fd, __buff, __cnt) read(__fd, __buff, __cnt)
#define _rename_r(__reent, __old, __new) rename(__old, __new)
#define _sbrk_r(__reent, __incr) sbrk(__incr)
#define _stat_r(__reent, __path, __buff) stat(__path, __buff)
#define _times_r(__reent, __time) times(__time)
#define _unlink_r(__reent, __path) unlink(__path)
#define _wait_r(__reent, __status) wait(__status)
#define _write_r(__reent, __fd, __buff, __cnt) write(__fd, __buff, __cnt)
#define _gettimeofday_r(__reent, __tp, __tzp) gettimeofday(__tp, __tzp)
#ifdef __LARGE64_FILES
#define _lseek64_r(__reent, __fd, __off, __w) lseek64(__fd, __off, __w)
#define _fstat64_r(__reent, __fd, __buff) fstat64(__fd, __buff)
#define _open64_r(__reent, __path, __flag, __m) open64(__path, __flag, __m)
#endif
#else
/* Reentrant versions of system calls. */
extern int _close_r (struct _reent *, int);
extern int _execve_r (struct _reent *, const char *, char *const *, char *const *);
extern int _fcntl_r (struct _reent *, int, int, int);
extern int _fork_r (struct _reent *);
extern int _fstat_r (struct _reent *, int, struct stat *);
extern int _getpid_r (struct _reent *);
extern int _isatty_r (struct _reent *, int);
extern int _kill_r (struct _reent *, int, int);
extern int _link_r (struct _reent *, const char *, const char *);
extern _off_t _lseek_r (struct _reent *, int, _off_t, int);
extern int _mkdir_r (struct _reent *, const char *, int);
extern int _open_r (struct _reent *, const char *, int, int);
extern _ssize_t _read_r (struct _reent *, int, void *, size_t);
extern int _rename_r (struct _reent *, const char *, const char *);
extern void *_sbrk_r (struct _reent *, ptrdiff_t);
extern int _stat_r (struct _reent *, const char *, struct stat *);
extern _CLOCK_T_ _times_r (struct _reent *, struct tms *);
extern int _unlink_r (struct _reent *, const char *);
extern int _wait_r (struct _reent *, int *);
extern _ssize_t _write_r (struct _reent *, int, const void *, size_t);
/* This one is not guaranteed to be available on all targets. */
extern int _gettimeofday_r (struct _reent *, struct timeval *__tp, void *__tzp);
#ifdef __LARGE64_FILES
#if defined(__CYGWIN__)
#define stat64 stat
#endif
struct stat64;
extern _off64_t _lseek64_r (struct _reent *, int, _off64_t, int);
extern int _fstat64_r (struct _reent *, int, struct stat64 *);
extern int _open64_r (struct _reent *, const char *, int, int);
extern int _stat64_r (struct _reent *, const char *, struct stat64 *);
/* Don't pollute namespace if not building newlib. */
#if defined (__CYGWIN__) && !defined (_LIBC)
#undef stat64
#endif
#endif
#endif
#ifdef __cplusplus
}
#endif
#endif /* _REENT_H_ */