TheRock/compiler/amd-llvm/lld/test/COFF/gnu-weak.test

RUN: lld-link -lldmingw %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe
RUN: lld-link -lld-allow-duplicate-weak %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe
RUN: not lld-link %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe 2>&1 | FileCheck %s --check-prefix=DEFAULT-ERROR

DEFAULT-ERROR: error: duplicate symbol: weakfunc


GNU ld can handle several definitions of the same weak symbol, and
unless there is a strong definition of it, it just picks the first
weak definition encountered.

(LLD extends this, to prefer an actual concrete definition of it,
over a definition in the form of absolute null.)

For each of the weak definitions, GNU tools produce a regular symbol
named .weak.<weaksymbol>.<othersymbol>, where the other symbol name is
another symbol defined close by.

The bundled object files can be produced from test code that looks like
this:

$ cat gnu-weak.c
void weakfunc(void) __attribute__((weak));
void otherfunc(void);

__attribute__((weak)) void weakfunc() {
}

int main(int argc, char* argv[]) {
    otherfunc();
    weakfunc();
    return 0;
}
void mainCRTStartup(void) {
    main(0, (char**)0);
}
void __main(void) {
}

$ cat gnu-weak2.c
void weakfunc(void) __attribute__((weak));

__attribute__((weak)) void weakfunc() {
}

void otherfunc(void) {
}

$ x86_64-w64-mingw32-gcc -c -O2 gnu-weak.c
$ x86_64-w64-mingw32-gcc -c -O2 gnu-weak2.c

$ x86_64-w64-mingw32-nm gnu-weak.o | grep weakfunc
0000000000000000 T .weak.weakfunc.main
                 w weakfunc
$ x86_64-w64-mingw32-nm gnu-weak2.o | grep weakfunc
0000000000000000 T .weak.weakfunc.otherfunc
                 w weakfunc