I didn't get this reviewed previously so I'll try again for 4.7 ...

---------- Forwarded message ----------


Here's my attempt to fix PR c++/18016 so that we get a warning from

struct S {
 int i;
 S() : i(i) { }
};

As I said in the audit trail, -Winit-self is broken for C++ (PR
c++/34772) so I made this warn with
-Wuninitialized and not affected by -Winit-self.

Even if -Winit-self wasn't broken I don't think it applies here,
there's no valid reason to initialize a member with itself, if you
really want to leave a member uninitialized then don't use a
mem-initializer in the constructor (which will work at least until
someone fixes PR c++/2972)

cp/ChangeLog:

       PR c++/18016
       * init.c (perform_member_init): Check for self-initialization.


testsuite/ChangeLog:

       PR c++/18016
       * g++.dg/warn/pr18016.C: New.


tested x86_64-linux with no regressions, ok for trunk?
Index: cp/init.c
===================================================================
--- cp/init.c   (revision 174044)
+++ cp/init.c   (working copy)
@@ -501,6 +501,17 @@
   if (decl == error_mark_node)
     return;
 
+  if (warn_uninitialized && init && TREE_CODE (init) == TREE_LIST
+      && TREE_CHAIN (init) == NULL_TREE)
+    {
+      tree val = TREE_VALUE (init);
+      if (TREE_CODE (val) == COMPONENT_REF && TREE_OPERAND (val, 1) == member
+         && TREE_OPERAND (val, 0) == current_class_ref)
+       warning_at (DECL_SOURCE_LOCATION (current_function_decl),
+                   OPT_Wuninitialized, "%qD is initialized with itself",
+                   member);
+    }
+
   if (init == void_type_node)
     {
       /* mem() means value-initialization.  */
Index: testsuite/g++.dg/warn/pr18016.C
===================================================================
--- testsuite/g++.dg/warn/pr18016.C     (revision 0)
+++ testsuite/g++.dg/warn/pr18016.C     (revision 0)
@@ -0,0 +1,11 @@
+/* { dg-do compile } */
+/* { dg-options "-Wuninitialized" } */
+
+class X {
+  int i;
+  X() : i(i) { }   // { dg-warning "initialized with itself" }
+  X(int i) : i(i) { }
+  X(const X& x) : i(x.i) { }
+};
+
+// { dg-prune-output "In constructor" }

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