Re: _Countof operator and countof macro (C2y)

[Bruno Haible via Gnulib discussion list]

Paul Eggert wrote:
> I introduced CALLN to Emacs in 2015 and it has proved useful.

OK, since you say it's useful, let's make sure that gnulib's
countof macro supports this case. Done like this:


2025-06-07  Bruno Haible  <br...@clisp.org>

        stdcountof-h: Work around a clang bug.
        Reported by Basil L. Contovounesios <ba...@contovou.net> in
        <https://lists.gnu.org/archive/html/bug-gnulib/2025-06/msg00073.html>.
        * lib/stdcountof.in.h (_gl_verify_is_array): Disable the checking on
        clang.
        * tests/test-stdcountof-h.c (test_func): Add another test case.

diff --git a/lib/stdcountof.in.h b/lib/stdcountof.in.h
index 105cf209a5..683b1c7156 100644
--- a/lib/stdcountof.in.h
+++ b/lib/stdcountof.in.h
@@ -81,7 +81,8 @@ template <typename T> _gl_array_type_test<T> 
_gl_array_type_test_helper(T&);
 # endif
 #else
 /* In C, we can use typeof and __builtin_types_compatible_p.  */
-# if _GL_GNUC_PREREQ (3, 1) || defined __clang__
+/* Work around clang bug <https://github.com/llvm/llvm-project/issues/143284>. 
 */
+# if _GL_GNUC_PREREQ (3, 1) && ! defined __clang__ /* || defined __clang__ */
 #  define _gl_verify_is_array(a) \
     sizeof (struct { unsigned int _gl_verify_error_if_negative : 
__builtin_types_compatible_p (typeof (a), typeof (&*(a))) ? -1 : 1; })
 # else
diff --git a/tests/test-stdcountof-h.c b/tests/test-stdcountof-h.c
index cd7e03f331..5d0a9a6611 100644
--- a/tests/test-stdcountof-h.c
+++ b/tests/test-stdcountof-h.c
@@ -58,6 +58,11 @@ test_func (int parameter[3])
   ASSERT (countof (unbounded) >= 0);
 #endif
 
+  {
+    extern int a, b, c;
+    ASSERT (countof (((int[]) { a, b, c })) == 3);
+  }
+
   /* Check that countof(...) is an expression of type size_t.  */
 #if !defined __cplusplus && HAVE__GENERIC
   ASSERT (_Generic (countof (bounded),          size_t: 1, default: 0));