http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52806
--- Comment #4 from Akim Demaille <akim.demaille at gmail dot com> 2012-03-31 14:12:00 UTC --- (In reply to comment #1) > Oh well, changing this would be really trivial, but then people would have to > globally switch-on -std=c++11 (which may not be otherwise appropriate) while > working on removing (as much as possible) explicit zeros from C++98-era code. I don't think this comment makes sense: with what would you want them to replace these 0, since nullptr is not available? I'm having precisely this problem in Bison. I want it to deliver code which compiles without warning on the user side (so I cannot play with Autoconf to check for nullptr support), so I use # ifndef YY_NULL # if 201103L <= __cplusplus # define YY_NULL nullptr # else # define YY_NULL 0 # endif # endif Unfortunately the user *will* have warnings if she passes the warning flag but not -std=c++11. This is even worse for C++03. $ g++-mp-4.7 -std=c++03 -Wzero-as-null-pointer-constant /tmp/foo.cc /tmp/foo.cc:1:11: warning: zero as null pointer constant [-Wzero-as-null-pointer-constant] /tmp/foo.cc:2:11: error: 'nullptr' was not declared in this scope Or, be consistent with the flags that rejected when misused (such as -Wmissing-prototypes that does not apply to C++) and reject that warning when not in std=c++11. The current status introduces non-killable warnings.
