re PR c/77767 (Side-effect from VLA array parameters lost)

	PR c/77767
	* c-decl.c (grokdeclarator): If *expr is non-NULL, append expression
	to *expr instead of overwriting it.

	* gcc.c-torture/execute/pr77767.c: New test.

From-SVN: r243832

gcc/c/ChangeLog

+2016-12-21  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/77767
+	* c-decl.c (grokdeclarator): If *expr is non-NULL, append expression
+	to *expr instead of overwriting it.
+
 2016-12-20  Richard Biener  <rguenther@suse.de>
 
 	* gimple-parser.c (c_parser_gimple_compound_statement): Improve

gcc/c/c-decl.c

@@ -5580,11 +5580,21 @@ grokdeclarator (const struct c_declarator *declarator,
   if (TREE_CODE (type) == ERROR_MARK)
     return error_mark_node;
   if (expr == NULL)
-    expr = &expr_dummy;
+    {
+      expr = &expr_dummy;
+      expr_dummy = NULL_TREE;
+    }
   if (expr_const_operands == NULL)
     expr_const_operands = &expr_const_operands_dummy;
 
-  *expr = declspecs->expr;
+  if (declspecs->expr)
+    {
+      if (*expr)
+	*expr = build2 (COMPOUND_EXPR, TREE_TYPE (declspecs->expr), *expr,
+			declspecs->expr);
+      else
+	*expr = declspecs->expr;
+    }
   *expr_const_operands = declspecs->expr_const_operands;
 
   if (decl_context == FUNCDEF)

gcc/testsuite/ChangeLog

+2016-12-21  Jakub Jelinek  <jakub@redhat.com>
+
+	PR c/77767
+	* gcc.c-torture/execute/pr77767.c: New test.
+
 2016-12-20  Pat Haugen  <pthaugen@us.ibm.com>
 
 	* gcc.dg/sms-3.c: Add -fno-sched-pressure for powerpc.

gcc/testsuite/gcc.c-torture/execute/pr77767.c

+/* PR c/77767 */
+
+void
+foo (int a, int b[a++], int c, int d[c++])
+{
+  if (a != 2 || c != 2)
+    __builtin_abort ();
+}
+
+int
+main ()
+{
+  int e[10];
+  foo (1, e, 1, e);
+  return 0;
+}