[C PATCH] Fix initialization of flexible array members (PR c/56078)

[Jakub Jelinek]

Hi!

As discussed in the PR, while most of c-typeck.c handles
constructor_max_index == NULL the same as when
tree_int_cst_lt (constructor_max_index, some_index)
returns false, i.e. some_index is within bounds, there is one spot
that handles this incorrectly and one which doesn't consider NULL
constructor_max_index at all.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk?  The 20030305-1.c testcase is now rejected with hard
errors instead of resulting just in warnings and ignored initializers,
but I believe the error is right, initialization of nested flexible array
member is what is happening in the testcase and is invalid.

2013-01-24  Jakub Jelinek  <jakub@redhat.com>

	PR c/56078
	* c-typeck.c (set_nonincremental_init_from_string): If
	constructor_max_index is NULL, treat it as if tree_int_cst_lt
	returned false.
	(process_init_element): Likewise.

	* gcc.dg/pr56078.c: New test.
	* gcc.c-torture/compile/20030305-1.c: Add dg-error lines.

--- gcc/c/c-typeck.c.jj	2013-01-23 16:23:16.000000000 +0100
+++ gcc/c/c-typeck.c	2013-01-24 11:51:10.267238683 +0100
@@ -7574,7 +7574,9 @@ set_nonincremental_init_from_string (tre
   end = p + TREE_STRING_LENGTH (str);
 
   for (purpose = bitsize_zero_node;
-       p < end && !tree_int_cst_lt (constructor_max_index, purpose);
+       p < end
+       && !(constructor_max_index
+	    && tree_int_cst_lt (constructor_max_index, purpose));
        purpose = size_binop (PLUS_EXPR, purpose, bitsize_one_node))
     {
       if (wchar_bytes == 1)
@@ -8106,9 +8108,9 @@ process_init_element (struct c_expr valu
 			      true, braced_init_obstack);
       else if ((TREE_CODE (constructor_type) == ARRAY_TYPE
 	        || TREE_CODE (constructor_type) == VECTOR_TYPE)
-	       && (constructor_max_index == 0
-		   || tree_int_cst_lt (constructor_max_index,
-				       constructor_index)))
+	       && constructor_max_index
+	       && tree_int_cst_lt (constructor_max_index,
+				   constructor_index))
 	process_init_element (pop_init_level (1, braced_init_obstack),
 			      true, braced_init_obstack);
       else
--- gcc/testsuite/gcc.dg/pr56078.c.jj	2013-01-24 12:04:00.727858939 +0100
+++ gcc/testsuite/gcc.dg/pr56078.c	2013-01-24 12:03:10.000000000 +0100
@@ -0,0 +1,25 @@
+/* PR c/56078 */
+/* { dg-do run } */
+/* { dg-options "-std=gnu99" } */
+
+typedef __SIZE_TYPE__ size_t;
+extern int memcmp (const void *, const void *, size_t);
+extern void abort (void);
+
+struct T { int a; char b[]; };
+struct T t1 = { .a = 1, .b = "abcd", .b[0] = '2' };
+struct T t2 = { .a = 1, .b = "2bcd" };
+struct T t3 = { .a = 1, .b[2] = 'a' };
+struct T t4 = { .a = 1, .b = { '\0', '\0', 'a' } };
+struct T t5 = { .a = 1, .b = { [0] = 'a', [1] = 'b', [2] = 'c' } };
+struct T t6 = { .a = 1, .b[2] = 'c', .b[1] = 'x', .b[0] = 'a', .b[1] = 'b' };
+
+int
+main ()
+{
+  if (memcmp (t1.b, t2.b, sizeof ("abcd")) != 0
+      || memcmp (t3.b, t4.b, 3) != 0
+      || memcmp (t5.b, t6.b, 3) != 0)
+    abort ();
+  return 0;
+}
--- gcc/testsuite/gcc.c-torture/compile/20030305-1.c.jj	2008-09-05 12:54:15.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/20030305-1.c	2013-01-24 16:23:01.000000000 +0100
@@ -12,7 +12,7 @@ typedef struct {
 } s2_t;
 
 static s2_t s2_array[]= {
-    { 1, 4 },
-    { 2, 5 },
-    { 3, 6 }
+    { 1, 4 },	/* { dg-error "(initialization of flexible array member|near)" } */
+    { 2, 5 },	/* { dg-error "(initialization of flexible array member|near)" } */
+    { 3, 6 }	/* { dg-error "(initialization of flexible array member|near)" } */
 };

	Jakub