https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109956
--- Comment #3 from Pascal Cuoq <pascal_cuoq at hotmail dot com> --- @Andrew Pinski You don't even need to invoke the fact that this is an extension. GCC could reserve 17 bytes for each variable i of type “int”, and as long as “sizeof i” continued to evaluate to 4 (4 being the value of “sizeof(int)” for x86), no-one would be able to claim that GCC is not generating “correct” assembly code. This ticket is pointing out that the current behavior for initialized FAMs is suboptimal for programs that rely on the GCC extension, just like it would be suboptimal to reserve 17 bytes for each “int” variable for standard C programs (and I would open a ticket for it if I noticed such a behavior). It's not breaking anything and it may be inconvenient to change, and as a ticket that does not affect correctness, it can be ignored indefinitely. It's just a suggestion for smaller binaries that might also end up marginally faster as a result. @Martin Uecker Considering how casually phrased the description of FAMs was in C99 and remained in later standards (see https://stackoverflow.com/q/73497572/139746 for me trying to make sense of some of the relevant words), I doubt that the standard has anything to say about the compiler extension being discussed. But if you have convincing arguments, you could spend a few minutes filing a bug against Clang to tell them that they are making the binaries they generate too small and efficient.
