https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118375
Peter Damianov <peter0x44 at disroot dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |peter0x44 at disroot dot org --- Comment #4 from Peter Damianov <peter0x44 at disroot dot org> --- Also related, when investigating PR80042 I ran in to this case: #include <math.h> void f(void) { sincos(0, nullptr, nullptr); } which emits: <source>: In function 'f': <source>:4:5: error: implicit declaration of function 'sincos' [-Wimplicit-function-declaration] 4 | sincos(0, nullptr, nullptr); | ^~~~~~ <source>:2:1: note: include '<math.h>' or provide a declaration of 'sincos' 1 | #include <math.h> +++ |+#include <math.h> 2 | void f(void) <source>:4:5: warning: incompatible implicit declaration of built-in function 'sincos' [-Wbuiltin-declaration-mismatch] 4 | sincos(0, nullptr, nullptr); | ^~~~~~ <source>:4:5: note: include '<math.h>' or provide a declaration of 'sincos' Compiler returned: 1 for -std=gnuXX Of course this is much less common, but still misleading.