I wrote: > * Both clang and gcc seem to be happy with the same spelling of the > function attribute, which is fortunate. However, I seriously doubt > that bare "#ifdef __GNUC__" is going to be good enough. At the very > least there's going to need to be a compiler version test in there, > and we might end up needing to get the configure script involved.
After digging in gcc's release history, it seems they invented "-fsanitize=alignment" in GCC 5, so we can make this work for gcc by writing #if __GNUC__ >= 5 (the likely() macro already uses a similar approach). Can't say if that's close enough for clang too. regards, tom lane