On Monday 15 April 2024 10:49:43 Martin Storsjö wrote:
> Or just compiling a test C file with the corresponding
> MSVC version and looking at the generated object file to see what symbol
> reference it generated.
So... now I did an experiment with VC4.2 CL.EXE (first version which
generate code for msvcrt.dll) and VC4.1 CL.EXE (last version which
generate code for msvcr40.dll).
Source code:
float __cdecl fdiv(float a, float b) { return a / b; }
Compiled with:
CL.EXE /c /QIfdiv /O2
Both 4.1 and 4.2 versions of CL.EXE generated same obj file which under
objdump -dr looks like:
Disassembly of section .text:
00000000 <_fdiv>:
0: d9 44 24 04 flds 0x4(%esp)
4: 83 3d 00 00 00 00 00 cmpl $0x0,0x0
6: dir32 __adjust_fdiv
b: 75 06 jne 13 <_fdiv+0x13>
d: d8 74 24 08 fdivs 0x8(%esp)
11: eb 09 jmp 1c <_fdiv+0x1c>
13: ff 74 24 08 pushl 0x8(%esp)
17: e8 00 00 00 00 call 1c <_fdiv+0x1c>
18: DISP32 __adj_fdiv_m32
1c: c3 ret
So what does it say about __adjust_fdiv and __adj_fdiv_m32 symbols?
If my understanding is correct then __adjust_fdiv is global variable
and __adj_fdiv_m32 is a function which takes first float argument in x87
ST(0) register, second float argument on the stack and function itself
pops the stack (the second float argument).
Now I checked all versions of msvcrt40.dll libraries which I found
(including OS system versions) and all have symbol name "_adj_fdiv_m32"
in their import tables.
So does it mean that "_adj_fdiv_m32" (and possibly also all other _adj_*
symbols) use stdcall calling convention, and should be defined with
@SIZE suffix in the .def file?
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