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flat assembler > Linux > Can Fasm make .o ELF object files?[solved, thanks]

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vivik



Joined: 29 Oct 2016
Posts: 405
I need to make a small object file in assembly, so that I can link it with the rest of my C program. Can Fasm do that?

I actually need that for windows program, for mingw compiler, but it uses ELF format for object files.


Last edited by vivik on 03 Aug 2017, 19:22; edited 1 time in total
Post 03 Aug 2017, 16:10
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Tomasz Grysztar
Assembly Artist


Joined: 16 Jun 2003
Posts: 6862
Location: Kraków, Poland
The ELF object examples are included in the "fasm for Linux" package, so you may have missed them because you work on Windows. They look like:
Code:
; MSGDEMO.ASM ; fasm demonstration of assembling object files ; compile the program using commands like: ; fasm msgdemo.asm msgdemo.o ; fasm writemsg.asm writemsg.o ; ld msgdemo.o writemsg.o -o msgdemo format ELF section '.text' executable public _start _start: extrn writemsg mov esi,msg call writemsg mov eax,1 xor ebx,ebx int 0x80 section '.data' writeable msg db "Elves are coming!",0xA,0
Code:
; WRITEMSG.ASM format ELF section '.text' executable public writemsg writemsg: mov ecx,esi find_end: lodsb or al,al jnz find_end mov edx,esi sub edx,ecx mov eax,4 mov ebx,1 int 0x80 ret
Post 03 Aug 2017, 19:04
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system error



Joined: 01 Sep 2013
Posts: 671
As already stated by TG, you can compile ELF64 in Windows and produce the desired .o object file, exporting via public keywords. However, if you want to make it workable in windows, you should not use any of the Linux-specific services.

Code:
format ELF64 ;just compile it normally public business business: ;the non linux-specific code ret


That's it. You can then use them as GCC's extern in mingw via linking.

Code:
#include <stdio.h> extern void business(void); int main() { business(); return 0; }


Linking (I used TDM-GCC-64 btw)
Code:
gcc -m64 yourcode.c business.o -o yourcode.exe
Post 03 Aug 2017, 19:19
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