https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85672
--- Comment #11 from Marc Glisse <glisse at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #8) > My autotools-fu is too weak to come up with anything better but I'd be very > happy if you can suggest something cleaner. For the general case, the autoconf manual suggests having another file and using AH_BOTTOM([#include <post.h>]) to get it included at the end of config.h. However, in the specific case of c++config.h in libstdc++, we are building it manually in include/Makefile.am: sed ... < ${glibcxx_srcdir}/include/bits/c++config > $@ sed ... < ${CONFIG_HEADER} >> $@ echo "" >> $@ echo "#endif // _GLIBCXX_CXX_CONFIG_H" >> $@ If we wanted to, it wouldn't be hard to cat whatever >> $@ after CONFIG_HEADER. Since you have something that works now, there is no need to change it, but we should keep this in mind for next time.