Hi,
On 06/12/2013 07:46 PM, Jason Merrill wrote:
On 06/12/2013 01:37 PM, Paolo Carlini wrote:
Rewording: as the one line comment says, I only call non_reference at
the outset when I know that either we'll end up producing the normal
unused-variable warning or nothing at all.
Oh, I see. But that's a rather subtle difference; better to have
'type' mean something consistent and leave the unused-but-set code
checking TREE_TYPE (decl).
Yeah. Earlier today I had something similar in my tree. I'm finishing
testing the below then.
Thanks,
Paolo.
Index: cp/decl.c
===================================================================
--- cp/decl.c (revision 200012)
+++ cp/decl.c (working copy)
@@ -622,17 +622,20 @@ poplevel (int keep, int reverse, int functionbody)
push_local_binding where the list of decls returned by
getdecls is built. */
decl = TREE_CODE (d) == TREE_LIST ? TREE_VALUE (d) : d;
+ // See through references for improved -Wunused-variable (PR 38958).
+ tree type = non_reference (TREE_TYPE (decl));
if (VAR_P (decl)
&& (! TREE_USED (decl) || !DECL_READ_P (decl))
&& ! DECL_IN_SYSTEM_HEADER (decl)
&& DECL_NAME (decl) && ! DECL_ARTIFICIAL (decl)
- && TREE_TYPE (decl) != error_mark_node
- && (!CLASS_TYPE_P (TREE_TYPE (decl))
- || !TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (decl))))
+ && type != error_mark_node
+ && (!CLASS_TYPE_P (type)
+ || !TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type)))
{
if (! TREE_USED (decl))
warning (OPT_Wunused_variable, "unused variable %q+D", decl);
else if (DECL_CONTEXT (decl) == current_function_decl
+ // For -Wunused-but-set-variable leave references alone.
&& TREE_CODE (TREE_TYPE (decl)) != REFERENCE_TYPE
&& errorcount == unused_but_set_errorcount)
{
Index: testsuite/g++.dg/warn/Wunused-var-20.C
===================================================================
--- testsuite/g++.dg/warn/Wunused-var-20.C (revision 0)
+++ testsuite/g++.dg/warn/Wunused-var-20.C (working copy)
@@ -0,0 +1,19 @@
+// PR c++/38958
+// { dg-options "-Wunused" }
+
+volatile int g;
+
+struct Lock
+{
+ ~Lock() { g = 0; }
+};
+
+Lock AcquireLock() { return Lock(); }
+
+int main()
+{
+ const Lock& lock = AcquireLock();
+ g = 1;
+ g = 2;
+ g = 3;
+}
