On 23 May 2011 03:07, Jason Merrill wrote:
> On 05/22/2011 05:11 PM, Jonathan Wakely wrote:
>>
>> As I said in the audit trail, -Winit-self is broken for C++ (PR
>> c++/34772)
>
> Not anymore. :)
Aha!
>> 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)
>
> ...at which point we would want it to be controlled by -Winit-self, so let's
> use -Winit-self now.
I still think this warning shouldn't be tied to -Winit-self. That
isn't included in -Wall or -Wextra, and it implies we're saying that a
self-referencing mem-initializer is a GNU extension to silence a
warning, when I think it's always a mistake and never done
intentionally. But I can live with that.
> OK with that change.
Thanks, I've attached what I committed. I only checked
warn_init_self, not both warn_uninitialized && warn_init_self, I think
that's right.
I've also just noticed that my change doesn't catch references which
are initialized with themselves. I won't try to fix that now, but
would that be done by checking for INDIRECT_REF?
I also had some thoughts about making init-self work for class types e.g.
std::string s = s;
Would checking if the copy constructor's parameter is *this be a
simple way to catch that?
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_init_self && 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 -Winit-self" } */
+
+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" }
