On 01/17/2018 01:44 PM, Jason Merrill wrote:
This makes sense to me. But I think we'd want also that flag set on
the ck_identity inside the ck_base that direct_reference_binding
creates, so setting it first rather than in an else.
Ah yes, you spotted the bit I failed to mention. (I think we get away
with it because class objects always have sufficient lvalueness, but why
lie?)
nathan
--
Nathan Sidwell
2018-01-18 Nathan Sidwell <nat...@acm.org>
PR c++/83160
* cp-tree.h (mark_use): Declare.
* expr.c (mark_use): Make extern.
* call.c (direct_reference_binding): Set inner conv's
rvaluedness_matches_p, if it is an identity.
(convert_like_real): Mark lvalue or rvalue use for identity as
rvaledness_matches_p demands.
PR c++/83160
* g++.dg/cpp0x/pr83160.C: New.
Index: cp/call.c
===================================================================
--- cp/call.c (revision 256841)
+++ cp/call.c (working copy)
@@ -102,7 +102,8 @@ struct conversion {
being bound to an lvalue expression or an rvalue reference is
being bound to an rvalue expression. If KIND is ck_rvalue,
true when we are treating an lvalue as an rvalue (12.8p33). If
- KIND is ck_base, always false. */
+ KIND is ck_base, always false. If ck_identity, we will be
+ binding a reference directly. */
BOOL_BITFIELD rvaluedness_matches_p: 1;
BOOL_BITFIELD check_narrowing: 1;
/* The type of the expression resulting from the conversion. */
@@ -1476,6 +1477,10 @@ direct_reference_binding (tree type, con
t = TREE_TYPE (type);
+ if (conv->kind == ck_identity)
+ /* Mark the identity conv as to not decay to rvalue. */
+ conv->rvaluedness_matches_p = true;
+
/* [over.ics.rank]
When a parameter of reference type binds directly
@@ -1501,6 +1506,7 @@ direct_reference_binding (tree type, con
That way, convert_like knows not to generate a temporary. */
conv->need_temporary_p = false;
}
+
return build_conv (ck_ref_bind, type, conv);
}
@@ -6800,7 +6806,9 @@ convert_like_real (conversion *convs, tr
else
gcc_unreachable ();
}
- expr = mark_rvalue_use (expr);
+ expr = mark_use (expr, /*rvalue_p=*/!convs->rvaluedness_matches_p,
+ /*read_p=*/true, UNKNOWN_LOCATION,
+ /*reject_builtin=*/true);
if (type_unknown_p (expr))
expr = instantiate_type (totype, expr, complain);
Index: cp/cp-tree.h
===================================================================
--- cp/cp-tree.h (revision 256841)
+++ cp/cp-tree.h (working copy)
@@ -6328,6 +6328,9 @@ extern tree create_try_catch_expr
/* in expr.c */
extern tree cplus_expand_constant (tree);
+extern tree mark_use (tree expr, bool rvalue_p, bool read_p,
+ location_t = UNKNOWN_LOCATION,
+ bool reject_builtin = true);
extern tree mark_rvalue_use (tree,
location_t = UNKNOWN_LOCATION,
bool reject_builtin = true);
Index: cp/expr.c
===================================================================
--- cp/expr.c (revision 256841)
+++ cp/expr.c (working copy)
@@ -89,7 +89,7 @@ cplus_expand_constant (tree cst)
/* We've seen an actual use of EXPR. Possibly replace an outer variable
reference inside with its constant value or a lambda capture. */
-static tree
+tree
mark_use (tree expr, bool rvalue_p, bool read_p,
location_t loc /* = UNKNOWN_LOCATION */,
bool reject_builtin /* = true */)
Index: testsuite/g++.dg/cpp0x/pr83160.C
===================================================================
--- testsuite/g++.dg/cpp0x/pr83160.C (revision 0)
+++ testsuite/g++.dg/cpp0x/pr83160.C (working copy)
@@ -0,0 +1,33 @@
+// { dg-do run { target c++11 } }
+// PR c++/83160 failed to capture as lvalue
+
+int main ()
+{
+ const int a = 0;
+
+ if (![&a] (const int *p)
+ {
+ const int &b = a;
+ // We should bind to the outer a
+ return &b == p;
+ } (&a))
+ return 1;
+
+ if (![&] (const int *p)
+ {
+ const int &b = a;
+ // We should bind to the outer a
+ return &b == p;
+ } (&a))
+ return 2;
+
+ if ([=] (const int *p)
+ {
+ const int &b = a;
+ // We should bind to the captured instance
+ return &b == p;
+ }(&a))
+ return 3;
+
+ return 0;
+}
