------- Comment #3 from redi at gcc dot gnu dot org 2010-06-11 11:37 ------- 'y' and 'C' are both promoted to int and 'y' is not a constant, so the resulting value cannot be proven to fit in a char, so it's a narrowing conversion.
If you make 'y' a const int then the value y+C is a constant and can be proven not to narrow. The fact that the optimiser knows y=42 is irrelevant, the language specifies that y is not a constant, and whether the code is valid or not has to be independent of optimisations such as value propagation. I think gcc is correct here. -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44500
