c: After issuing errors about array size, for error-recovery don't make the array VLA [PR93573]

After we report various errors about array size, we set for error-recovery
the size to be 1, but because size_int_const is false, it still means we
pretend the array is a VLA, can emit a second diagnostics in that case etc.
E.g.
$ ./cc1.unpatched -quiet a.c
a.c:1:5: error: size of array ‘f’ has non-integer type
    1 | int f[100.0];
      |     ^
a.c:1:1: warning: variably modified ‘f’ at file scope
    1 | int f[100.0];
      | ^~~
$ ./cc1 -quiet a.c
a.c:1:5: error: size of array ‘f’ has non-integer type
    1 | int f[100.0];
      |     ^

2020-03-28  Jakub Jelinek  <jakub@redhat.com>

	PR c/93573
	* c-decl.c (grokdeclarator): After issuing errors, set size_int_const
	to true after setting size to integer_one_node.

	* gcc.dg/pr93573-1.c: New test.
	* gcc.dg/pr93573-2.c: New test.

gcc/ChangeLog

 2020-03-28  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/93573
+	* c-decl.c (grokdeclarator): After issuing errors, set size_int_const
+	to true after setting size to integer_one_node.
+
 	PR tree-optimization/94329
 	* tree-ssa-reassoc.c (reassociate_bb): When calling reassoc_remove_stmt
 	on the last stmt in a bb, make sure gsi_prev isn't done immediately

gcc/c/c-decl.c

@@ -6416,6 +6416,7 @@ grokdeclarator (const struct c_declarator *declarator,
 		      error_at (loc,
 				"size of unnamed array has non-integer type");
 		    size = integer_one_node;
+		    size_int_const = true;
 		  }
 		/* This can happen with enum forward declaration.  */
 		else if (!COMPLETE_TYPE_P (TREE_TYPE (size)))
@@ -6427,6 +6428,7 @@ grokdeclarator (const struct c_declarator *declarator,
 		      error_at (loc, "size of unnamed array has incomplete "
 				"type");
 		    size = integer_one_node;
+		    size_int_const = true;
 		  }
 
 		size = c_fully_fold (size, false, &size_maybe_const);
@@ -6451,6 +6453,7 @@ grokdeclarator (const struct c_declarator *declarator,
 			else
 			  error_at (loc, "size of unnamed array is negative");
 			size = integer_one_node;
+			size_int_const = true;
 		      }
 		    /* Handle a size folded to an integer constant but
 		       not an integer constant expression.  */

gcc/testsuite/ChangeLog

 2020-03-28  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c/93573
+	* gcc.dg/pr93573-1.c: New test.
+	* gcc.dg/pr93573-2.c: New test.
+
 	PR tree-optimization/94329
 	* gfortran.dg/pr94329.f90: New test.
 

gcc/testsuite/gcc.dg/pr93573-1.c

+/* PR c/93573 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+void bar ();
+
+void
+foo (char a)
+{
+  union C { int d[100.0]; char *e; };	/* { dg-error "has non-integer type" } */
+  bar ((union C) &a);
+}

gcc/testsuite/gcc.dg/pr93573-2.c

+/* PR c/93573 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+int f[100.0];	/* { dg-error "has non-integer type" } */
+                /* { dg-bogus "variably modified .f. at file scope" "" { target *-*-* } .-1 } */