From: Joseph Myers <josmyers@redhat.com>
Date: Wed, 31 Jan 2024 21:39:53 +0000 (+0000)
Subject: c: Fix ICE for nested enum redefinitions with/without fixed underlying type [PR112571]
X-Git-Tag: basepoints/gcc-15~1470
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d22d1a9346f27db41459738c6eb404f8f0956e6f;p=thirdparty%2Fgcc.git

c: Fix ICE for nested enum redefinitions with/without fixed underlying type [PR112571]

Bug 112571 reports an ICE-on-invalid for cases where an enum is
defined, without a fixed underlying type, inside the enum type
specifier for a definition of that same enum with a fixed underlying
type.

The ultimate cause is attempting to access ENUM_UNDERLYING_TYPE in a
case where it is NULL.  Avoid this by clearing
ENUM_FIXED_UNDERLYING_TYPE_P in thie case of inconsistent definitions.

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

	PR c/112571

gcc/c/
	* c-decl.cc (start_enum): Clear ENUM_FIXED_UNDERLYING_TYPE_P when
	defining without a fixed underlying type an enumeration previously
	declared with a fixed underlying type.

gcc/testsuite/
	* gcc.dg/c23-enum-9.c, gcc.dg/c23-enum-10.c: New tests.
---

diff --git a/gcc/c/c-decl.cc b/gcc/c/c-decl.cc
index 8d18a3e11f46..934e557dc3bb 100644
--- a/gcc/c/c-decl.cc
+++ b/gcc/c/c-decl.cc
@@ -9905,8 +9905,11 @@ start_enum (location_t loc, struct c_enum_contents *the_enum, tree name,
 
   if (ENUM_FIXED_UNDERLYING_TYPE_P (enumtype)
       && fixed_underlying_type == NULL_TREE)
-    error_at (loc, "%<enum%> declared with but defined without "
-	      "fixed underlying type");
+    {
+      error_at (loc, "%<enum%> declared with but defined without "
+		"fixed underlying type");
+      ENUM_FIXED_UNDERLYING_TYPE_P (enumtype) = false;
+    }
 
   the_enum->enum_next_value = integer_zero_node;
   the_enum->enum_type = enumtype;
diff --git a/gcc/testsuite/gcc.dg/c23-enum-10.c b/gcc/testsuite/gcc.dg/c23-enum-10.c
new file mode 100644
index 000000000000..dd5f3453b1f3
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c23-enum-10.c
@@ -0,0 +1,6 @@
+/* PR c/112571.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+enum X : typeof (enum X { A }); /* { dg-error "declared with but defined without fixed underlying type" } */
+/* { dg-error "invalid 'enum' underlying type" "invalid" { target *-*-* } .-1 } */
diff --git a/gcc/testsuite/gcc.dg/c23-enum-9.c b/gcc/testsuite/gcc.dg/c23-enum-9.c
new file mode 100644
index 000000000000..10bb493ca3ce
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/c23-enum-9.c
@@ -0,0 +1,8 @@
+/* PR c/112571.  */
+/* { dg-do compile } */
+/* { dg-options "-std=c23" } */
+
+enum h : typeof (enum h { D }) { D }; /* { dg-error "declared with but defined without fixed underlying type" } */
+/* { dg-error "invalid 'enum' underlying type" "invalid" { target *-*-* } .-1 } */
+/* { dg-error "nested redefinition" "nested" { target *-*-* } .-2 } */
+/* { dg-error "conflicting redefinition" "conflicting" { target *-*-* } .-3 } */