C PATCH to enhance array bounds diagnostics (PR c/69262)

diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index 915376d..1644478 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -5951,6 +5951,18 @@  grokdeclarator (const struct c_declarator *declarator,
 	      {
 		error_at (loc, "array type has incomplete element type %qT",
 			  type);
+		/* See if we can be more helpful.  */
+		if (TREE_CODE (type) == ARRAY_TYPE)
+		  {
+		    if (name)
+		      inform (loc, "declaration of %qE as multidimensional "
+			      "array must have bounds for all dimensions "
+			      "except the first", name);
+		    else
+		      inform (loc, "declaration of multidimensional array "
+			      "must have bounds for all dimensions except "
+			      "the first");
+		  }
 		type = error_mark_node;
 	      }
 	    else
diff --git gcc/testsuite/gcc.dg/array-15.c gcc/testsuite/gcc.dg/array-15.c
index e69de29..a002f68 100644
--- gcc/testsuite/gcc.dg/array-15.c
+++ gcc/testsuite/gcc.dg/array-15.c
@@ -0,0 +1,52 @@ 
+/* PR c/69262 */
+/* { dg-do compile } */
+/* { dg-options "-std=c11 -pedantic-errors" } */
+
+struct S
+{
+  int a[1][][2]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-message "declaration of .a. as multidimensional array must have bounds" "" { target *-*-* } 7 } */
+};
+
+struct R
+{
+  int i;
+  int a[][]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-message "declaration of .a. as multidimensional array must have bounds" "" { target *-*-* } 14 } */
+};
+
+typedef int T[];
+typedef int U[][]; /* { dg-error "array type has incomplete element type" } */
+/* { dg-message "declaration of .U. as multidimensional array must have bounds" "" { target *-*-* } 19 } */
+
+int x[][]; /* { dg-error "array type has incomplete element type" } */
+/* { dg-message "declaration of .x. as multidimensional array must have bounds" "" { target *-*-* } 22 } */
+
+struct N;
+
+void
+fn1 (int z[][]) /* { dg-error "array type has incomplete element type" } */
+/* { dg-message "declaration of .z. as multidimensional array must have bounds" "" { target *-*-* } 28 } */
+{
+  int a[1][][2]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-message "declaration of .a. as multidimensional array must have bounds" "" { target *-*-* } 31 } */
+  /* OK */
+  int b[3][2][1];
+  int c[1][2][3][]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-message "declaration of .c. as multidimensional array must have bounds" "" { target *-*-* } 35 } */
+  T d[1]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-message "declaration of .d. as multidimensional array must have bounds" "" { target *-*-* } 37 } */
+  T e[]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-message "declaration of .e. as multidimensional array must have bounds" "" { target *-*-* } 39 } */
+
+  /* This array has incomplete element type, but is not multidimensional.  */
+  struct N f[1]; /* { dg-error "array type has incomplete element type" } */
+  /* { dg-bogus "declaration of .f. as multidimensional array must have bounds" "" { target *-*-* } 43 } */
+}
+
+void fn2 (int [][]); /* { dg-error "array type has incomplete element type" } */
+/* { dg-message "declaration of multidimensional array must have bounds" "" { target *-*-* } 47 } */
+/* OK */
+void fn3 (int [][*]);
+void fn4 (T []); /* { dg-error "array type has incomplete element type" } */
+/* { dg-message "declaration of multidimensional array must have bounds" "" { target *-*-* } 51 } */