http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54025
--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-07-19 11:57:04 UTC --- If we just do the change and nothing else, 20_util/duration/cons/constexpr.cc doesn't compile anymore with this error: /scratch/Gcc/svn-dirs/trunk/libstdc++-v3/testsuite/20_util/duration/cons/constexpr.cc:27:42: required from here /scratch/Gcc/svn-dirs/trunk/libstdc++-v3/testsuite/util/testsuite_common_types.h:698:18: error: uninitialized const '__obj' [-fpermissive] { constexpr _Tp __obj; } ^ In file included from /scratch/Gcc/svn-dirs/trunk/libstdc++-v3/testsuite/20_util/duration/cons/constexpr.cc:21:0: /home/paolo/Gcc/svn-dirs/trunk-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/chrono:220:14: note: 'const struct std::chrono::duration<long int>' has no user-provided default constructor struct duration ^ /home/paolo/Gcc/svn-dirs/trunk-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/chrono:231:12: note: constructor is not user-provided because it is explicitly defaulted in the class body constexpr duration() = default; ^ /home/paolo/Gcc/svn-dirs/trunk-build/x86_64-unknown-linux-gnu/libstdc++-v3/include/chrono:349:6: note: and the implicitly-defined constructor does not initialize 'std::chrono::duration<long int>::rep std::chrono::duration<long int>::__r' rep __r; ^