My recent work on fixing lifetime extension for temporaries bound to
references makes it trivial to add this warning.
Tested x86_64-pc-linux-gnu, applied to trunk.
commit 1db25121594ff9405adeb5bd6892d72679bf2ba1
Author: Jason Merrill <ja...@redhat.com>
Date: Sat Nov 12 20:42:21 2011 -0500
PR c++/986
* call.c (set_up_extended_ref_temp): Warn about references
bound to non-static reference members.
* init.c (perform_member_init): Pass in the member.
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index dd3026d..181d9e8 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -8609,6 +8609,14 @@ set_up_extended_ref_temp (tree decl, tree expr, VEC(tree,gc) **cleanups,
if (TREE_CODE (expr) != TARGET_EXPR)
expr = get_target_expr (expr);
+ if (TREE_CODE (decl) == FIELD_DECL
+ && extra_warnings && !TREE_NO_WARNING (decl))
+ {
+ warning (OPT_Wextra, "a temporary bound to %qD only persists "
+ "until the constructor exits", decl);
+ TREE_NO_WARNING (decl) = true;
+ }
+
/* Recursively extend temps in this initializer. */
TARGET_EXPR_INITIAL (expr)
= extend_ref_init_temps (decl, TARGET_EXPR_INITIAL (expr), cleanups);
diff --git a/gcc/cp/init.c b/gcc/cp/init.c
index 888c151..73f2b67 100644
--- a/gcc/cp/init.c
+++ b/gcc/cp/init.c
@@ -623,7 +623,7 @@ perform_member_init (tree member, tree init)
if (init == error_mark_node)
return;
/* Use 'this' as the decl, as it has the lifetime we want. */
- init = extend_ref_init_temps (current_class_ptr, init, &cleanups);
+ init = extend_ref_init_temps (member, init, &cleanups);
if (TREE_CODE (type) == ARRAY_TYPE
&& TYPE_HAS_NONTRIVIAL_DESTRUCTOR (TREE_TYPE (type)))
init = build_vec_init_expr (type, init, tf_warning_or_error);
diff --git a/gcc/testsuite/g++.dg/warn/ref-temp1.C b/gcc/testsuite/g++.dg/warn/ref-temp1.C
new file mode 100644
index 0000000..26f1ca5
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/ref-temp1.C
@@ -0,0 +1,11 @@
+// PR c++/986
+// { dg-options "-Wall -Wextra" }
+
+struct X { X (int); };
+
+struct Y {
+ Y ();
+ const X &x; // note the ampersand
+};
+
+Y::Y () : x(1) {} // { dg-warning "temporary" }