I'm trying to write a simple assembly program that does not rely on an I/O, and assemble into a 32-bit native Windows executable (that is using mingw toolchain not cygwin). Here's what I have (I haven't written any assembly in decades, so this may not be correct, that's fine, I am trying to (re)learn). The program tests some register and then jumps to a location given by the register eax
section .text
global _main
_main:
mov eax, 0x00401000
cmp eax, 0
jz .L1
inc eax
jmp .L2
.L1:
add eax, 2
.L2:
jmp eax
Assemble using nasm:
nasm.exe -f win32 -g -o test_branch.o test_branch.asm
I am running 64bit cygwin but am using the 32bit cross linker
i686-w64-mingw32-ld.exe -o test_branch.exe -mi386pe test_branch.o
(tried both with and without -mi386pe) Unfortunately, this is still linking with 64 bit DLLs, not with the 32 bit DLLs as the following run of gdb shows:
$ gdb test_branch.exe
GNU gdb (GDB) (Cygwin 8.3.1-1) 8.3.1
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Reading symbols from test_branch.exe...
(No debugging symbols found in test_branch.exe)
(gdb) r
Starting program: test_branch.exe
warning: `/cygdrive/c/WINDOWS/SYSTEM32/ntdll.dll': Shared library architecture i386:x86-64 is not compatible with target architecture i386.
warning: `/cygdrive/c/WINDOWS/System32/wow64.dll': Shared library architecture i386:x86-64 is not compatible with target architecture i386.
warning: `/cygdrive/c/WINDOWS/System32/wow64win.dll': Shared library architecture i386:x86-64 is not compatible with target architecture i386.
warning: dll path for "WOW64_IMAGE_SECTION" can not be evaluated
warning: Could not load shared library symbols for WOW64_IMAGE_SECTION.
Do you need "set solib-search-path" or "set sysroot"?
warning: dll path for "WOW64_IMAGE_SECTION" can not be evaluated
warning: Could not load shared library symbols for WOW64_IMAGE_SECTION.
Do you need "set solib-search-path" or "set sysroot"?
warning: dll path for "WOW64_IMAGE_SECTION" can not be evaluated
warning: Could not load shared library symbols for WOW64_IMAGE_SECTION.
Do you need "set solib-search-path" or "set sysroot"?
warning: `/cygdrive/c/WINDOWS/System32/wow64cpu.dll': Shared library architecture i386:x86-64 is not compatible with target architecture i386.
[New Thread 30828.0x7d8c]
Thread 1 received signal SIGSEGV, Segmentation fault.
0x7783cfa0 in ?? ()
(gdb)
So I guess my question is 1. how do i convince the linker to use the 32 bit DLLs and 2. Assuming I don't have them, which ones will I need to download (would rather know the full list ahead of time rather than discover missing dll's at runtime). I have looked at compile 32bit code from cygwin64 but I didn't get any insights. 3. Why does gdb say there are no debugging symbols even though i used the -g option in nasm?
