On 30/09/2024 22:26, Nathan Chancellor wrote: > Hi Javier, > > On Mon, Sep 30, 2024 at 06:50:14PM +0200, Javier Carrasco wrote: >> But if that wasn't the case, and since you can't use sizeof(<type>), >> should it be marked with __maybe_unused / __attribute__((unused)) even >> though it's known in advance that it won't be used, or at least that its >> use will be to get its size? > > Correct. > >> Is it then just to silence the warning, or does it have other >> implications? Thanks again! > > Yes, the use of the unused attribute would just be to silence the > warning; the variable would still not be emitted in the final binary. > clang's behavior matches GCC's (aside from the special warning): > > https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-unused-variable-attribute > > If the variable needed to be emitted in the object file, > __attribute__((used)) would need to be used, which explicitly has code > generation implications: > > https://gcc.gnu.org/onlinedocs/gcc/Common-Variable-Attributes.html#index-used-variable-attribute > > A contrived example: > > https://godbolt.org/z/oGGbqK98o > > Cheers, > Nathan Thanks a lot for spoon-feeding it to me :) Best regards, Javier Carrasco
