[clang][clang-cl][x86]In Windows 32-bit, the program generated using assembly language cannot run properly.

[romanholidaypancakes]

1. test.cpp

#include "stdio.h"
#include <windows.h>


int main() {
    printf("hello world");
    MessageBoxW(0, 0, L"hello world", 0);
    return 0;
}

2. generate assembly

clang-cl -m32 test.cpp /clang:-S

3. generating programs from assembler file

clang-cl user32.lib -m32 test.asm -o test32.exe

4. When running test32.exe, it crashes upon calling MessageBoxW, indicating a failure to properly relocate imported functions. However, the same command runs successfully on the 64-bit version of the program.

[alvinhochun]

The generated assembly is

	call	dword ptr [__imp__MessageBoxW@16]

When compiling from the source to binary directly, this is the disassembly:

007d103f ff1510417e00    call    dword ptr [test62010+0x14110 (007e4110)]

When compiling from the assembly, this is what I got instead:

00b8103f e8cc300100      call    test62010_b+0x14110 (00b94110)

Looks like LLVM may be doing something odd with Intel asm syntax: https://godbolt.org/z/YWvrn75YG

[romanholidaypancakes]

https://godbolt.org/z/PP8W9W3W7

• 32

_main:                                  # @main
        push    ebp
        mov     ebp, esp
        sub     esp, 16
        xor     eax, eax
        lea     eax, ["??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"]
        mov     dword ptr [esp], 0
        mov     dword ptr [esp + 4], 0
        mov     dword ptr [esp + 8], eax
        mov     dword ptr [esp + 12], 0
        call    dword ptr [__imp__MessageBoxW@16]
        sub     esp, 16
        xor     eax, eax
        add     esp, 16
        pop     ebp
        ret
"??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@":

• 64

main:                                   # @main
        sub     rsp, 40
        xor     eax, eax
        mov     edx, eax
        lea     r8, [rip + "??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@"]
        xor     r9d, r9d
        mov     rcx, rdx
        call    qword ptr [rip + __imp_MessageBoxW]
        xor     eax, eax
        add     rsp, 40
        ret
"??_C@_1BI@HHJHKLLN@?$AAh?$AAe?$AAl?$AAl?$AAo?$AA?5?$AAw?$AAo?$AAr?$AAl?$AAd?$AA?$AA@":

64 will use rip relocation

[romanholidaypancakes]

the assembly generated by gcc can be compiled and run normally

	.file	"test.cpp"
	.intel_syntax noprefix
	.text
	.def	___main;	.scl	2;	.type	32;	.endef
	.section .rdata,"dr"
LC0:
	.ascii "hello world\0"
	.align 2
LC1:
	.ascii "h\0e\0l\0l\0o\0 \0w\0o\0r\0l\0d\0\0\0"
	.text
	.globl	_main
	.def	_main;	.scl	2;	.type	32;	.endef
_main:
LFB516:
	.cfi_startproc
	lea	ecx, [esp+4]
	.cfi_def_cfa 1, 0
	and	esp, -16
	push	DWORD PTR [ecx-4]
	push	ebp
	.cfi_escape 0x10,0x5,0x2,0x75,0
	mov	ebp, esp
	push	ecx
	.cfi_escape 0xf,0x3,0x75,0x7c,0x6
	sub	esp, 20
	call	___main
	mov	DWORD PTR [esp], OFFSET FLAT:LC0
	call	_printf
	mov	DWORD PTR [esp+12], 0
	mov	DWORD PTR [esp+8], OFFSET FLAT:LC1
	mov	DWORD PTR [esp+4], 0
	mov	DWORD PTR [esp], 0
	mov	eax, DWORD PTR __imp__MessageBoxW@16
	call	eax
	sub	esp, 16
	mov	eax, 0
	mov	ecx, DWORD PTR [ebp-4]
	.cfi_def_cfa 1, 0
	leave
	.cfi_restore 5
	lea	esp, [ecx-4]
	.cfi_def_cfa 4, 4
	ret
	.cfi_endproc
LFE516:
	.ident	"GCC: (i686-win32-dwarf-rev0, Built by MinGW-W64 project) 8.1.0"
	.def	_printf;	.scl	2;	.type	32;	.endef

[llvmbot]

@llvm/issue-subscribers-backend-x86

[alvinhochun]

https://reviews.llvm.org/D149579

[alvinhochun]

Should be fixed in trunk.