[C PATCH] Fix ICE-on-invalid with enum forward declaration (PR c/70851)

[Marek Polacek]

Here, the problem was that we weren't diagnosing invalid code when an array
dimension was of incomplete enum type.  That led to an ICE in gimplifier.

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

2016-05-02  Marek Polacek  <pola...@redhat.com>

        PR c/70851
        * c-decl.c (grokdeclarator): Diagnose when array's size has an
        incomplete type.

        * gcc.dg/enum-incomplete-3.c: New test.

diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index 16e4250..7094efc 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -5799,10 +5799,21 @@ grokdeclarator (const struct c_declarator *declarator,
                  {
                    if (name)
                      error_at (loc, "size of array %qE has non-integer type",
-                               name);
+                               name);
                    else
                      error_at (loc,
-                               "size of unnamed array has non-integer type");
+                               "size of unnamed array has non-integer type");
+                   size = integer_one_node;
+                 }
+               /* This can happen with enum forward declaration.  */
+               else if (!COMPLETE_TYPE_P (TREE_TYPE (size)))
+                 {
+                   if (name)
+                     error_at (loc, "size of array %qE has incomplete type",
+                               name);
+                   else
+                     error_at (loc, "size of unnamed array has incomplete "
+                               "type");
                    size = integer_one_node;
                  }
 
diff --git gcc/testsuite/gcc.dg/enum-incomplete-3.c 
gcc/testsuite/gcc.dg/enum-incomplete-3.c
index e69de29..db1138b 100644
--- gcc/testsuite/gcc.dg/enum-incomplete-3.c
+++ gcc/testsuite/gcc.dg/enum-incomplete-3.c
@@ -0,0 +1,20 @@
+/* PR c/70851 */
+/* { dg-do compile } */
+/* { dg-options "" } */
+
+enum E e; /* { dg-error "storage size" } */
+
+void bar (int [e]); /* { dg-error "size of unnamed array has incomplete type" 
} */
+void bar2 (int [][e]); /* { dg-error "size of unnamed array has incomplete 
type" } */
+
+void
+foo (void)
+{
+  int a1[e]; /* { dg-error "size of array .a1. has incomplete type" } */
+  int a2[e][3]; /* { dg-error "size of array .a2. has incomplete type" } */
+
+  struct S
+  {
+    int a3[e]; /* { dg-error "size of array .a3. has incomplete type" } */
+  };
+}

        Marek