For some unknown reason, certain functions from advapi32.dll are now
also exported by the kernel32.dll of recent Windows versions. To provide
backward compatibility, -ladvapi32 must occur before -lkernel32 in the
linker command, but this is not the case by default:
Testcase with current packages from Cygwin (10.0.0-1, GCC 11.2.0-1):
$ cat testdll.c
#include <windows.h>
int (*fp)() = CreateProcessAsUserA;
int main() { return 42; }
$ x86_64-w64-mingw32-gcc -o testdll1 testdll.c
$ x86_64-w64-mingw32-gcc -o testdll2 testdll.c -ladvapi32
$ objdump -p testdll1.exe | egrep 'DLL Name|CreateProcessAsUserA'
DLL Name: KERNEL32.dll
82ac 235 CreateProcessAsUserA
DLL Name: msvcrt.dll
$ objdump -p testdll2.exe | egrep 'DLL Name|CreateProcessAsUserA'
DLL Name: ADVAPI32.dll
82d0 1138 CreateProcessAsUserA
DLL Name: KERNEL32.dll
DLL Name: msvcrt.dll
Both work on Win10, but only testdll2 works on Win7.
The root of the problem is that the libgcc rule in the specs contains
another -lkernel32:
$ x86_64-w64-mingw32-gcc -dumpspecs
...
*lib:
... -ladvapi32 -lshell32 -luser32 -lkernel32
...
*libgcc:
... -lmoldname -lmingwex -lmsvcrt -lkernel32
...
This -lkernel32 prepends the -ladvapi32 from the lib rule:
$ x86_64-w64-mingw32-gcc -o testdll1 testdll.c -v
...
/usr/lib/.../11/collect2.exe ... -lkernel32 ... -ladvapi32 ...
-lkernel32 ...
A modified specs file with '... -ladvapi32 -lkernel32' in the libgcc
rule would fix the problem.
I could add a report to gcc bugzilla if desired.
Regards,
Christian
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