(c_expand_return): Issue a warning if returning address of non-static

local object.

From-SVN: r6405

diff --git a/gcc/c-typeck.c b/gcc/c-typeck.c
index b952828cbe65b14f5697300dda21cbb2d0a76e85..f2f507d922df30132e9b0d7716cd3aafc8bf0664 100644 (file)
--- a/gcc/c-typeck.c
+++ b/gcc/c-typeck.c
@@ -1,5 +1,5 @@
 /* Build expressions with type checking for C compiler.
-   Copyright (C) 1987, 1988, 1989, 1992, 1993 Free Software Foundation, Inc.
+   Copyright (C) 1987, 88, 91, 92, 93, 1994 Free Software Foundation, Inc.
 
 This file is part of GNU CC.
 
@@ -6202,12 +6202,36 @@ c_expand_return (retval)
       tree t = convert_for_assignment (valtype, retval, "return",
                                       NULL_TREE, NULL_TREE, 0);
       tree res = DECL_RESULT (current_function_decl);
+      tree inner;
 
       if (t == error_mark_node)
        return;
 
-      t = build (MODIFY_EXPR, TREE_TYPE (res),
-                res, convert (TREE_TYPE (res), t));
+      inner = t = convert (TREE_TYPE (res), t);
+
+      /* Strip any conversions, additions, and subtractions, and see if
+        we are returning the address of a local variable.  Warn if so.  */
+      while (TREE_CODE (inner) == NOP_EXPR
+            || TREE_CODE (inner) == NON_LVALUE_EXPR
+            || TREE_CODE (inner) == CONVERT_EXPR
+            || TREE_CODE (inner) == PLUS_EXPR
+            || TREE_CODE (inner) == MINUS_EXPR)
+       inner = TREE_OPERAND (inner, 0);
+
+      if (TREE_CODE (inner) == ADDR_EXPR)
+       {
+         inner = TREE_OPERAND (inner, 0);
+
+         while (TREE_CODE_CLASS (TREE_CODE (inner)) == 'r')
+           inner = TREE_OPERAND (inner, 0);
+
+         if (TREE_CODE (inner) == VAR_DECL
+             && ! TREE_STATIC (inner)
+             && DECL_CONTEXT (inner) == current_function_decl)
+           warning ("function returns address of local variable");
+       }
+
+      t = build (MODIFY_EXPR, TREE_TYPE (res), res, t);
       TREE_SIDE_EFFECTS (t) = 1;
       expand_return (t);
       current_function_returns_value = 1;