https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63610
--- Comment #4 from Volker Braun <vbraun.name at gmail dot com> ---
I got my hands on a gcc 4.9.1 binary build made on OSX 10.9 and this one works.
Diffing the log shows that this is due to different linker flags, my binary
build calls
libtool: link: gcc -std=gnu99 -dynamiclib -Wl,-undefined -Wl,dynamic_lookup -o
.libs/libmpir.11.dylib [...]
whereas the Yosemite-bootstrapped gcc calls
libtool: link: gcc -std=gnu99 -dynamiclib -Wl,-flat_namespace -Wl,-undefined
-Wl,suppress -o .libs/libmpir.11.dylib [...]
Relinking with the previous linker flags fixes the segfault. This is most
likely due to incorrect aclocal.m4 case check
case ${MACOSX_DEPLOYMENT_TARGET-10.0},$host in
10.0,*86*-darwin8*|10.0,*-darwin[[91]]*)
_lt_dar_allow_undefined='${wl}-undefined ${wl}dynamic_lookup' ;;
10.[[012]]*)
_lt_dar_allow_undefined='${wl}-flat_namespace ${wl}-undefined
${wl}suppress' ;;
not taking 10.10 properly into account.
