http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50012
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> 2011-12-19 14:43:05 UTC --- This has been introduced with http://gcc.gnu.org/ml/gcc-patches/2009-06/msg01402.html which has been written as a better way of: http://gcc.gnu.org/ml/gcc-patches/2009-06/msg01393.html Perhaps the older patch is a better way than this one, which, if I understand it right, is that ignoring of the promotion at the -Wsign-compare handling spot? Setting TREE_NO_WARNING, at least until we have a way to say which warnings we want to prohibit and which should be kept, is an ugly hack and shouldn't be taken lightly. While Ian's patch doesn't set TREE_NO_WARNING in this testcase, it just disables the warning if any of the operands is TREE_NO_WARNING and uses this bit for yet another purpose. The TREE_NO_WARNING bit in this case is set by finish_parenthesized_expr: 1504 if (EXPR_P (expr)) 1505 /* This inhibits warnings in c_common_truthvalue_conversion. */ 1506 TREE_NO_WARNING (expr) = 1; So, what was wrong with the first approach? And, perhaps for 4.8 we want to turn TREE_NO_WARNING bit into a bit that just tells us whether that tree in question is in some hash table (see e.g. DECL_HAS_VALUE_EXPR_P etc.) and that hash table would contain details what warnings are we supposed to ignore. This isn't the only problematic spot.
