Bug#945133: gcc-9: __has_attribute(ifunc) false positive on hurd and kfreebsd

[Fabian Kloetzl <kloetzl@evolbio.mpg.de>]

Package: gcc-9
Version: 9.2.1-17
Severity: normal

Dear Maintainer,

Recently, the build of one of my packages failed on hurd-i386 and
kfreebsd-* due to unsupported ifuncs [1]. However, I had that code guarded
by __has_attribute(ifunc) which, unfortunately, evaluates to 1 on said
platforms. A minimal testcase is attached.

Best,
Fabian

1: https://buildd.debian.org/status/package.php?p=phylonium

#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