[PATCH] c: Fix up error-recovery on non-empty VLA initializers [PR109409]

[Jakub Jelinek <jakub@redhat.com>]

Hi!

On the following testcase we ICE, because after we emit the
variable-sized object may not be initialized except with an empty initializer
error we don't really reset the initializer to error_mark_node and then at
-Wformat checking time we ICE on seeing STRING_CST initializer for a VLA.

The following patch just arranges for error_mark_node to be returned after
the error diagnostics.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2023-04-14  Jakub Jelinek  <jakub@redhat.com>

	PR c/109409
	* c-parser.cc (c_parser_initializer): Move diagnostics about
	initialization of variable sized object with non-empty initializer
	after c_parser_expr_no_commas call and ret.set_error (); after it.

	* gcc.dg/pr109409.c: New test.

--- gcc/c/c-parser.cc.jj	2023-02-18 12:38:30.759025693 +0100
+++ gcc/c/c-parser.cc	2023-04-13 13:09:13.287373656 +0200
@@ -5677,11 +5677,14 @@ c_parser_initializer (c_parser *parser,
     {
       struct c_expr ret;
       location_t loc = c_parser_peek_token (parser)->location;
-      if (decl != error_mark_node && C_DECL_VARIABLE_SIZE (decl))
-	error_at (loc,
-		  "variable-sized object may not be initialized except "
-		  "with an empty initializer");
       ret = c_parser_expr_no_commas (parser, NULL);
+      if (decl != error_mark_node && C_DECL_VARIABLE_SIZE (decl))
+	{
+	  error_at (loc,
+		    "variable-sized object may not be initialized except "
+		    "with an empty initializer");
+	  ret.set_error ();
+	}
       /* This is handled mostly by gimplify.cc, but we have to deal with
 	 not warning about int x = x; as it is a GCC extension to turn off
 	 this warning but only if warn_init_self is zero.  */
--- gcc/testsuite/gcc.dg/pr109409.c.jj	2023-04-13 13:31:52.865765576 +0200
+++ gcc/testsuite/gcc.dg/pr109409.c	2023-04-13 13:13:26.994714440 +0200
@@ -0,0 +1,10 @@
+/* PR c/109409 */
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+void
+foo (int n)
+{
+  const char c[n] = "1";	/* { dg-error "variable-sized object may not be initialized except with an empty initializer" } */
+  __builtin_printf (c);
+}

	Jakub