https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105499
Andrew Pinski <pinskia at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Keywords|diagnostic |documentation --- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> --- __extension__ disables all compatibility warnings. This is by design really as headers sometimes needs to be written using C code and need to turn off these warnings. The documentation should mention that though like it does for -Wc90-c99-compat , -Wc99-c11-compat and -Wc11-c2x-compat . https://gcc.gnu.org/onlinedocs/gcc-12.2.0/gcc/Warning-Options.html#index-Wc_002b_002b-compat