As of eeff8cae, lib/stdcountof.in.h uses a bare typeof:
110 /* In C, we can use typeof and __builtin_types_compatible_p. */
111 /* Work around clang bug
<https://github.com/llvm/llvm-project/issues/143284>. */
112 # if _GL_GNUC_PREREQ (3, 1) && ! defined __clang__ /* || defined
__clang__ */
113 # define _gl_verify_is_array(...) \
114 sizeof (struct { unsigned int _gl_verify_error_if_negative :
__builtin_types_compatible_p (typeof (__VA_ARGS__), typeof
(&*(__VA_ARGS__))) ? -1 : 1; })
115 # else
116 /* The compiler does not have the necessary built-ins. */
117 # define _gl_verify_is_array(...) 0
118 # endif
119 #endif
https://gitweb.git.savannah.gnu.org/gitweb/?p=gnulib.git;a=blob;f=lib/stdcountof.in.h;h=1422629bf2838af99f342cd9ed021fa8c6afe1b3;hb=eeff8cae#l114
This breaks compiling gnutls with '-std=c99' (tested on Fedora 43 GCC 15.2.1):
uniwidth/width.c: In function 'uc_width':
uniwidth/width.c:61:19: error: unknown type name 'typeof'; did you
mean '__typeof__'?
61 | if ((uc >> 9) < countof (nonspacing_table_ind))
| ^~~~~~~
Another place suggesting __typeof__ for portability:
https://gcc.gnu.org/onlinedocs/gcc/Typeof.html
What probably made it surface:
https://lists.gnu.org/archive/html/bug-gnulib/2026-03/msg00013.html
