[Bug c/69507] bogus warning: ISO C does not allow ‘__alignof__ ?=(expression)=?UTF-8?Q?’

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69507

--- Comment #2 from Martin Sebor <msebor at gcc dot gnu.org> ---
The manual says this about -Wpedantic:

  -Wpedantic does not cause warning messages for use of the alternate keywords
whose names begin and end with '__'.

GCC accepts without a warning many extensions in pedantic mode, including
__attribute__((aligned)), __const__, and __inline__, all of which have
corresponding similar features in C, as well as __typeof__ which doesn't:

$ cat z.c && /home/msebor/build/gcc-trunk-git/gcc/xgcc
-B/home/msebor/build/gcc-trunk-git/gcc -S -Wall -Wextra -Wpedantic -std=c11 z.c
__const__ int a __attribute__ ((aligned));
__typeof__ (a) b;
__inline__ void f (void) { }