https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79345
--- Comment #11 from Richard Biener <rguenth at gcc dot gnu.org> --- Created attachment 40857 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40857&action=edit unreduced testcase for false positive Bootstrap issue #1 (I posted a reasonable workaround): > ./cc1plus -quiet -O2 -Wuninitialized -o /dev/null ~/fixed-value.ii In file included from /space/rguenther/src/svn/trunk/gcc/coretypes.h:365:0, from /space/rguenther/src/svn/trunk/gcc/fixed-value.c:22: /space/rguenther/src/svn/trunk/gcc/wide-int.h: In function ‘void fixed_from_string(fixed_value*, const char*, machine_mode)’: /space/rguenther/src/svn/trunk/gcc/wide-int.h:818:40: warning: ‘*((void*)& w +34359738360)’ may be used uninitialized in this function [-Wmaybe-uninitialized] unsigned HOST_WIDE_INT high = this->get_val ()[len - 1]; ~~~~~~~~~~~~~~~~^ /space/rguenther/src/svn/trunk/gcc/wide-int.h: In function ‘bool fixed_convert_from_real(fixed_value*, machine_mode, const real_value*, bool)’: /space/rguenther/src/svn/trunk/gcc/wide-int.h:818:40: warning: ‘*((void*)& w +34359738360)’ may be used uninitialized in this function [-Wmaybe-uninitialized] unsigned HOST_WIDE_INT high = this->get_val ()[len - 1]; ~~~~~~~~~~~~~~~~^