c: Do not remove _Atomic from array element type for typeof_unqual [PR117781]

[Joseph Myers]

As reported in bug 117781, my fix for bug 112841 broke the case of
typeof_unqual applied to an array of _Atomic elements, which should
not have _Atomic removed since only the element type is atomic, not
the array type.  Fix with logic to ensure that atomic element types
are preserved as such, while other qualifiers (i.e. those that are
semantically rather than only syntactically such in C) are removed.

Bootstrapped with no regressions for x86_64-pc-linux-gnu.

        PR c/117781

gcc/c/
        * c-parser.cc (c_parser_typeof_specifier): Do not remove _Atomic
        from array element type for typeof_unqual.

gcc/testsuite/
        * gcc.dg/c23-typeof-5.c: New test.

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index 48683572d7cd..9a2b19c10a7a 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -4443,9 +4443,19 @@ c_parser_typeof_specifier (c_parser *parser)
   parens.skip_until_found_close (parser);
   if (ret.spec != error_mark_node)
     {
-      if (is_unqual
-         && TYPE_QUALS (strip_array_types (ret.spec)) != TYPE_UNQUALIFIED)
-       ret.spec = TYPE_MAIN_VARIANT (ret.spec);
+      if (is_unqual)
+       {
+         bool is_array = TREE_CODE (ret.spec) == ARRAY_TYPE;
+         int quals = TYPE_QUALS (strip_array_types (ret.spec));
+         if ((is_array ? quals & ~TYPE_QUAL_ATOMIC : quals)
+             != TYPE_UNQUALIFIED)
+           {
+             ret.spec = TYPE_MAIN_VARIANT (ret.spec);
+             if (quals & TYPE_QUAL_ATOMIC && is_array)
+               ret.spec = c_build_qualified_type (ret.spec,
+                                                  TYPE_QUAL_ATOMIC);
+           }
+       }
       if (is_std)
        {
          /* In ISO C terms, _Noreturn is not part of the type of
diff --git a/gcc/testsuite/gcc.dg/c23-typeof-5.c 
b/gcc/testsuite/gcc.dg/c23-typeof-5.c
new file mode 100644
index 000000000000..e8076982822d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c23-typeof-5.c
@@ -0,0 +1,18 @@
+/* Test C23 typeof and typeof_unqual on arrays of atomic elements (bug
+   117781).  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
+
+_Atomic int a[2], b[2][2];
+const _Atomic int c[2], d[2][2];
+
+extern typeof (a) a;
+extern typeof (b) b;
+extern typeof (c) c;
+extern typeof (d) d;
+extern typeof_unqual (a) a;
+extern typeof_unqual (b) b;
+extern typeof_unqual (c) a;
+extern typeof_unqual (d) b;
+extern typeof_unqual (volatile _Atomic int [2]) a;
+extern typeof_unqual (volatile _Atomic int [2][2]) b;

-- 
Joseph S. Myers
josmy...@redhat.com