Diagnose array assignment for C90 (PR 58235)

Diagnose array assignment for C90 (PR 58235)

[Joseph S. Myers]

This patch fixes bug 58235, a corner case with non-lvalue arrays in
C90 where the assignment of a non-lvalue array to an expression with
array type was not diagnosed.  A specific check is added for
assignments to arrays (which are never valid).

Bootstrapped with no regressions on x86_64-unknown-linux-gnu.  Applied
to mainline.

c:
2013-12-02  Joseph Myers  <joseph@codesourcery.com>

	PR c/58235
	* c-typeck.c (build_modify_expr): Diagnose assignment to
	expression with array type.

testsuite:
2013-12-02  Joseph Myers  <joseph@codesourcery.com>

	PR c/58235
	* gcc.dg/c90-array-lval-8.c: New test.

Index: testsuite/gcc.dg/c90-array-lval-8.c
===================================================================
--- testsuite/gcc.dg/c90-array-lval-8.c	(revision 0)
+++ testsuite/gcc.dg/c90-array-lval-8.c	(revision 0)
@@ -0,0 +1,20 @@
+/* Test for non-lvalue arrays: test that they cannot be assigned to
+   array variables.  PR 58235.  */
+/* { dg-do compile } */
+/* { dg-options "-std=iso9899:1990 -pedantic-errors" } */
+
+struct s { char c[1]; } x;
+struct s f (void) { return x; }
+
+void
+g (void)
+{
+  char c[1];
+  c = f ().c; /* { dg-error "array" } */
+}
+
+void
+h (void)
+{
+  char c[1] = f ().c; /* { dg-error "array" } */
+}
Index: c/c-typeck.c
===================================================================
--- c/c-typeck.c	(revision 205585)
+++ c/c-typeck.c	(working copy)
@@ -5205,6 +5205,14 @@ build_modify_expr (location_t location, tree lhs,
   if (TREE_CODE (lhs) == ERROR_MARK || TREE_CODE (rhs) == ERROR_MARK)
     return error_mark_node;
 
+  /* Ensure an error for assigning a non-lvalue array to an array in
+     C90.  */
+  if (TREE_CODE (lhstype) == ARRAY_TYPE)
+    {
+      error_at (location, "assignment to expression with array type");
+      return error_mark_node;
+    }
+
   /* For ObjC properties, defer this check.  */
   if (!objc_is_property_ref (lhs) && !lvalue_or_else (location, lhs, lv_assign))
     return error_mark_node;

-- 
Joseph S. Myers
joseph@codesourcery.com