https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66424
--- Comment #4 from Zhendong Su <su at cs dot ucdavis.edu> --- (In reply to jos...@codesourcery.com from comment #3) > See C11 6.5.2.2#6 regarding when calls to unprototyped functions involve > undefined behavior. Being able to represent the value is only relevant > where the case is a mismatch of corresponding signed/unsigned types. Joseph, thank you for the clarification. I assume that you were referring to the following passage of C11 6.5.2.2 #6: "If the function is defined with a type that does not include a prototype, and the types of the arguments after promotion are not compatible with those of the parameters after promotion, the behavior is undefined, except for the following cases ... " Since int and long long are incompatible, thus the test case's behavior is undefined. Correct? If I may ask a follow-up question: How GCC treats the test case seems to have changed from 4.9 to 5.1. What might have prompted the change as the 4.9 behavior to me seems more natural and user-friendly (and is also how clang behaves)? Thank you.
