https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68115
--- Comment #5 from Ian Lance Taylor <ian at airs dot com> --- The HAVE_SYNC_FUNCTIONS test is in libbacktrace/internal.h, and it #define's the functions. You can see that that is happening because the warning is about a macro expansion. It looks like we just need to add some sort of cast to disable the warning in this specific case. For the use when target_subdir is set, my understanding has been that targets will either define the sync builtins directly or provide a version in the support libraries. If that is not the case, then we need to edit libbacktrace/configure.ac to recognize some cases where the sync functions are not available.
