[Libvir] Turn on compiler buffer checks

Since testing the latest Fedora RPMs I've hit a number of buffer overflow issues which were caught by the extra compiler checks Fedora turns on. It would be much better if we caught these before release, so the attached patch modifies the configure script so that the following options are always turned on if the compiler supports them: -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -fstack-protector --param=ssp-buffer-size=4 -fasynchronous-unwind-tables Since all our production builds use these flags & the patch only enables them if the compiler has support I don't see any issue with having them turned on by default. In addition I altered the existing configure compiler flag checks so that every compiler flag we turned on is explicitly checked to see if supported by the current compiler rather than doing a crude $CC=gcc heuristic which doesn't take account of differing gcc version numbers. If we wanted super-extra paranoia we could also turn on -fstack-protector-all possibly only with --enable-compiler-warnings=maximum since it adds more non-trivial performance overhead Regards, Dan. -- |=- Red Hat, Engineering, Emerging Technologies, Boston. +1 978 392 2496 -=| |=- Perl modules: http://search.cpan.org/~danberr/ -=| |=- Projects: http://freshmeat.net/~danielpb/ -=| |=- GnuPG: 7D3B9505 F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 -=|