GCC: Bad return code before reaching main when fprintf is linked with aarch64-w64-mingw32-g++ executable

[Blackhex]

Issue

When the following C/C++ code:

#include <stdio.h>

int main () {
    FILE *f = fopen ("test.txt", "w");
    fprintf (f, "%d\n", 10);
    return 0;
}

is compiled with aarch64-w64-mingw32-g++ the control flow does not reach main and return code 127 or 123 is returned.

• When the same code is compiled with aarch64-w64-mingw32-gcc, it works fine.
• When fprintf line is removed, it works fine.
• Other functions like printf work fine.
• When object files are produced from this source code first, both with aarch64-w64-mingw32-gcc and aarch64-w64-mingw32-g++ they are identical and when then they are linked with aarch64-w64-mingw32-g++ it fails while with aarch64-w64-mingw32-gcc it works.
• The issue happens only when shared runtime libraries are linked, with -static the binary works fine.
• It seems that the C++ linked binaries are not loading libgcc_s_seh-1.dll correctly while C linked ones does.
• Disassembled EXE produced by aarch64-w64-mingw32-g++ bad-exe.txt and by aarch64-w64-mingw32-gcc good-exe.txt linkers are showing some differences.

[ZacWalk]

Interesting: fprintf itself is part of the C standard library, using it in a C++ program might indirectly trigger the initialization of parts of the C++ standard library. Constructors etc.

@Blackhex it might be worth taking a look at .init_array or the ctors list in the c++ output. Looking at the disam, ctors looks the same for both but a little weird for c++

0000000140008d78 <__CTOR_LIST__>:
   140008d78:	ffffffff 	.inst	0xffffffff ; undefined
   140008d7c:	ffffffff 	.inst	0xffffffff ; undefined`