https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69310
--- Comment #12 from Jack Howarth <howarth.at.gcc at gmail dot com> --- I can confirm that the following change allows current gcc trunk to bootstrap on x86_64-apple-darwin15. Index: libstdc++-v3/config/os/bsd/darwin/os_defines.h =================================================================== --- libstdc++-v3/config/os/bsd/darwin/os_defines.h (revision 232606) +++ libstdc++-v3/config/os/bsd/darwin/os_defines.h (working copy) @@ -47,4 +47,7 @@ #define _GLIBCXX_USE_NANOSLEEP 1 #define _GLIBCXX_USE_SCHED_YIELD 1 +// No support for referencing weak symbols without a definition. +#define _GLIBCXX_USE_WEAK_REF 0 + #endif
