Build: Require attribute no_profile_instrument_function for ifunc usage.

Using __attribute__((__no_profile_instrument_function__)) on the ifunc
resolver works around a bug in GCC -fprofile-generate:
it adds profiling code even to ifunc resolvers which can make
the ifunc resolver crash at program startup. This attribute
was not introduced until GCC 7 and Clang 13, so ifunc won't
be used with prior versions of these compilers.

This bug was brought to our attention by:

    https://bugs.gentoo.org/925415

And was reported to upstream GCC by:

    https://gcc.gnu.org/bugzilla/show_bug.cgi?id=11411

1 files changed, 7 insertions, 0 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index b45002d8..3b616b5c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1082,6 +1082,13 @@ if(USE_ATTR_IFUNC STREQUAL "auto")
             #endif
 
             static void func(void) { return; }
+
+            /*
+            * The attribute __no_profile_instrument_function__ is
+            * needed with GCC to prevent improper instrumentation in
+            * the ifunc resolver.
+            */
+            __attribute__((__no_profile_instrument_function__))
             static void (*resolve_func(void)) (void) { return func; }
             void func_ifunc(void)
                     __attribute__((__ifunc__(\"resolve_func\")));