C PATCH for c/71426 (ICE with bogus parameter)

[Marek Polacek]

cc1 crashed on the following invalid code, because it tripped this assert.
The reason why b->nested was false for the FUNCTION_DECL 'x' was that when
doing pushdecl, we found an incompatible duplicate, so pushdecl just bound
'x' to FUNCTION_DECL 'x', replacing the old binding, without the TREE_PUBLIC
test that sets 'nested'.

At first I thought about removing the assert but in the end I decided to add
|| seen_error -- for invalid code we might do the same as for ERROR_MARK.

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

2016-06-07  Marek Polacek  <polacek@redhat.com>

	PR c/71426
	* c-decl.c (get_parm_info): Don't crash on an assert on invalid
	code.

	* gcc.dg/noncompile/pr71426.c: New test.

diff --git gcc/c/c-decl.c gcc/c/c-decl.c
index d79802e..8ceb8ba 100644
--- gcc/c/c-decl.c
+++ gcc/c/c-decl.c
@@ -7054,9 +7054,9 @@ get_parm_info (bool ellipsis, tree expr)
 	  break;
 
 	case FUNCTION_DECL:
-	  /*  FUNCTION_DECLs appear when there is an implicit function
-	      declaration in the parameter list.  */
-	  gcc_assert (b->nested);
+	  /* FUNCTION_DECLs appear when there is an implicit function
+	     declaration in the parameter list.  */
+	  gcc_assert (b->nested || seen_error ());
 	  goto set_shadowed;
 
 	case CONST_DECL:
diff --git gcc/testsuite/gcc.dg/noncompile/pr71426.c gcc/testsuite/gcc.dg/noncompile/pr71426.c
index e69de29..874e189 100644
--- gcc/testsuite/gcc.dg/noncompile/pr71426.c
+++ gcc/testsuite/gcc.dg/noncompile/pr71426.c
@@ -0,0 +1,5 @@
+/* PR c/71426 */
+/* { dg-do compile } */
+/* { dg-options "-w" } */
+
+int f (int x[x - x ()]); /* { dg-error "undeclared" } */

	Marek