Can an OMF file generated by Windows tools be linked into a GCC assembly in linux?

Question

I am porting a Windows VC++ application to Linux that links to an assembler module currently produced by MASM. After changing its Windows ABI assumptions to Linux ABI, I would like to again assemble the module on MASM to OMF (in Windows), then directly input that object file into the GCC build (in Linux). This would greatly simplify maintenance over time and guarantee an identical assembly under both operating systems. The alternative is porting the assembler code to YASM/NASM and its complications. The assembler code is entirely leaf routines (no calls), with no macros, no Unicode data and scant integer/real data; it includes 32-bit and a 64-bit assembler versions. Barring endian issues, does it really matter whose tool chain generates the OMF representation for this module?

Answer 1

I tested out it out using a simple test case and it worked fine when linked using the GNU linker under Linux. So you probably don't need to do anything special.

Here's the assembly file I tested it with:

_TEXT   SEGMENT USE32
    PUBLIC  foo
foo:
    mov eax, 1234
    ret
_TEXT   ENDS

    END

And here's the C program:

#include <stdio.h>

extern int foo();

int
main() {
        printf("%d\n", foo());
        return 0;
}

I assembled the first file on Windows using MASM, copied the resulting .OBJ file to a Linux machine (Debian x86_64) and compiled/linked it with the following command:

gcc -m32 main.c foo.obj

Running the generated executable (a.out) produced the expected output: 1234. I also tested the equivalent 64-bit case and it worked as well.

Unless you're dependent on PECOFF-specific section (segment) ordering or other PECOFF-specific features it looks like you shouldn't have any problems, at least far the object file format goes. Note it's possible that the version of the GNU linker installed on your Linux machine wasn't built with support for PECOFF. In that case you may need to build your own version from source.