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[Clang] On GCC, C23 typeof strips noreturn attribute on function pointers #176070
Description
https://godbolt.org/z/e8M18778s
[[gnu::noreturn]]
extern void(*fptr)(void);
int typeof_ext(int i, __typeof(fptr) p) {
p();
return i; // not emitted because p is noreturn
}
int typeof_std(int i, typeof(fptr) p) {
p();
return i; // emitted on GCC C23
}When under C23 and using the standard (not underscored) spelling of typeof, GCC would remove the noreturn attribute from the function pointer type.
From GCC's commit message (gcc-mirror/gcc@fa258f6) this seems to be intentional.
Could be dangerous if someone rely on this behavior and only test with GCC.
Activity
shafik commentedon Jan 15, 2026
CC @AaronBallman
llvmbot commentedon Jan 15, 2026
@llvm/issue-subscribers-clang-frontend
Author: Hsiang-Ying Fu (fuhsnn)
Details
https://godbolt.org/z/e8M18778s ```C [[gnu::noreturn]] extern void(*fptr)(void);int typeof_ext(int i, __typeof(fptr) p) {
p();
return i; // not emitted because p is noreturn
}
int typeof_std(int i, typeof(fptr) p) {
p();
return i; // emitted on GCC C23
}
AaronBallman commentedon Jan 16, 2026
I think this requires more thought; I'm not currently comfortable with the approach GCC took for several reasons. 1) users don't expect a difference between
__typeof__andtypeofso this introduces a fun new footgun for them to reason about, 2) typeof should not be stripping type information; that creates an arms race where we then will find a need fortypeof_but_for_real_this_timein cases where you actually want the real type as the type system sees it.Note, Clang and GCC are already divergent in how we handle noreturn attributes; Clang treats
__attribute__((noreturn))and[[gnu::noreturn]]as being a fundamental part of the type. So you can do things like:typedef void func(void) __attribute__((noreturn));in Clang andfunchas the expected type annotation effects; the same is not true in GCC where they ignore the attribute despite treating it as part of the function type in other scenarios: https://godbolt.org/z/d7xsT5Exq