[Bug preprocessor/93419] New: __has_attribute(ifunc) false positive on hurd and kfreebsd

[fabian-gcc at kloetzl dot info]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93419

            Bug ID: 93419
           Summary: __has_attribute(ifunc) false positive on hurd and
                    kfreebsd
           Product: gcc
           Version: 9.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: preprocessor
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fabian-gcc at kloetzl dot info
  Target Milestone: ---

Hi all,

Hereby I am forwarding a bug I filed against Debian [1]. One of my packages
there failed to build on hurd-i386 and kfreebsd-* due to unsupported ifuncs.
However, I had that code guarded by __has_attribute(ifunc) which,
unfortunately, evaluates to 1 on said platforms. A minimal testcase is given
below.

Best,
Fabian

1: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=945133


-----

#include <stdio.h>

int main() {
        return 0;
}

#if __has_attribute(ifunc)

typedef void (fntype)(void);
fntype* fn_select(void) {
        return NULL;
}

void fn(void) __attribute__((ifunc("fn_select")));

#endif