[gcc r15-5598] c: Fix typeof_unqual handling of qualified array types [PR112841]

[Joseph Myers via Gcc-cvs]

https://gcc.gnu.org/g:84a335eb4f9641a471184d86900609dd97215218

commit r15-5598-g84a335eb4f9641a471184d86900609dd97215218
Author: Joseph Myers <josmy...@redhat.com>
Date:   Fri Nov 22 20:33:10 2024 +0000

    c: Fix typeof_unqual handling of qualified array types [PR112841]
    
    As reported in bug 112841, typeof_unqual fails to remove qualifiers
    from qualified array types.  In C23 (unlike in previous standard
    versions), array types are considered to have the qualifiers of the
    element type, so typeof_unqual should remove such qualifiers (and an
    example in the standard shows that is as intended).  Fix this by
    calling strip_array_types when checking for the presence of
    qualifiers.  (The reason we check for qualifiers rather than just
    using TYPE_MAIN_VARIANT unconditionally is to avoid, as a quality of
    implementation matter, unnecessarily losing typedef information in the
    case where the type is already unqualified.)
    
    Bootstrapped with no regressions for x86_64-pc-linux-gnu.
    
            PR c/112841
    
    gcc/c/
            * c-parser.cc (c_parser_typeof_specifier): Call strip_array_types
            when checking for type qualifiers for typeof_unqual.
    
    gcc/testsuite/
            * gcc.dg/c23-typeof-4.c: New test.

Diff:
---
 gcc/c/c-parser.cc                   |  3 ++-
 gcc/testsuite/gcc.dg/c23-typeof-4.c | 10 ++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/gcc/c/c-parser.cc b/gcc/c/c-parser.cc
index f3ed61047477..44d344fcd32a 100644
--- a/gcc/c/c-parser.cc
+++ b/gcc/c/c-parser.cc
@@ -4444,7 +4444,8 @@ c_parser_typeof_specifier (c_parser *parser)
   parens.skip_until_found_close (parser);
   if (ret.spec != error_mark_node)
     {
-      if (is_unqual && TYPE_QUALS (ret.spec) != TYPE_UNQUALIFIED)
+      if (is_unqual
+         && TYPE_QUALS (strip_array_types (ret.spec)) != TYPE_UNQUALIFIED)
        ret.spec = TYPE_MAIN_VARIANT (ret.spec);
       if (is_std)
        {
diff --git a/gcc/testsuite/gcc.dg/c23-typeof-4.c 
b/gcc/testsuite/gcc.dg/c23-typeof-4.c
new file mode 100644
index 000000000000..471d08293414
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c23-typeof-4.c
@@ -0,0 +1,10 @@
+/* Test C23 typeof and typeof_unqual on qualified arrays (bug 112841).  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23 -pedantic-errors" } */
+
+const int a[] = { 1, 2, 3 };
+int b[3];
+extern typeof (a) a;
+extern typeof (const int [3]) a;
+extern typeof_unqual (a) b;
+extern typeof_unqual (const int [3]) b;