check_c_source_runs(
    "extern int __attribute__((weak)) foo(); int main() { return &foo == 0 ? 0 : 1; }"
    HAVE_WEAK_ATTRIBUTE)

check_c_source_compiles("
#define WEAK __attribute__((weak))

WEAK int sum(int a, int b)
{
    return a + b;
}

int main(void)
{
    int i = sum(2, 2);

    (void)i;

    return 0;
}" HAVE_WEAK_ATTRIBUTE)