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Re: [PATCH] PR c++/66735 lambda capture by reference
On 01/04/2017 12:36 AM, Jason Merrill wrote:
On 01/03/2017 08:57 AM, Nathan Sidwell wrote:
+ type = auto_node;
+ if (by_reference_p)
+ type = build_reference_type (type);
+ by_reference_p = false;
^^^ here
+ if (!is_this && by_reference_p)
+ type = build_reference_type (type);
This looks like it will call build_reference_type twice in the explicit
init case, producing a reference to reference.
Note the clearing of by_reference_p just above in this case, but I admit
that's confusing. Anyway, it's rendered moot by this patch which addresses:
if (DECLTYPE_FOR_LAMBDA_CAPTURE (t))
type = lambda_capture_field_type (type,
- DECLTYPE_FOR_INIT_CAPTURE (t));
+ DECLTYPE_FOR_INIT_CAPTURE (t),
+ /*by_reference_p=*/false);
Always passing false seems unlikely to be correct.
I wondered about that, but obviously failed to come up with a testcase
to expose it. This patch adds such a case, and exposes the need to add
another flag to DECLTYPE to indicate reference capture -- rather than
wrap the dependent capture in a reference type itself, as was previously
the case.
ok?
nathan
--
Nathan Sidwell
2017-01-04 Nathan Sidwell <nathan@acm.org>
cp/
PR c++/66735
* cp-tree.h (DECLTYPE_FOR_REF_CAPTURE): New.
(lambda_capture_field_type): Update prototype.
* lambda.c (lambda_capture_field_type): Add is_reference parm.
Add referenceness here.
(add_capture): Adjust lambda_capture_field_type call, refactor
error checking.
* pt.c (tsubst): Adjust lambda_capture_field_type call.
testsuite/
PR c++/66735
* g++.dg/cpp1y/pr66735.C: New.
Index: cp/cp-tree.h
===================================================================
--- cp/cp-tree.h (revision 244054)
+++ cp/cp-tree.h (working copy)
@@ -181,6 +181,7 @@ operator == (const cp_expr &lhs, tree rh
BIND_EXPR_BODY_BLOCK (in BIND_EXPR)
DECL_NON_TRIVIALLY_INITIALIZED_P (in VAR_DECL)
CALL_EXPR_ORDERED_ARGS (in CALL_EXPR, AGGR_INIT_EXPR)
+ DECLTYPE_FOR_REF_CAPTURE (in DECLTYPE_TYPE)
4: TREE_HAS_CONSTRUCTOR (in INDIRECT_REF, SAVE_EXPR, CONSTRUCTOR,
CALL_EXPR, or FIELD_DECL).
IDENTIFIER_TYPENAME_P (in IDENTIFIER_NODE)
@@ -4103,6 +4104,8 @@ more_aggr_init_expr_args_p (const aggr_i
TREE_LANG_FLAG_1 (DECLTYPE_TYPE_CHECK (NODE))
#define DECLTYPE_FOR_LAMBDA_PROXY(NODE) \
TREE_LANG_FLAG_2 (DECLTYPE_TYPE_CHECK (NODE))
+#define DECLTYPE_FOR_REF_CAPTURE(NODE) \
+ TREE_LANG_FLAG_3 (DECLTYPE_TYPE_CHECK (NODE))
/* Nonzero for VAR_DECL and FUNCTION_DECL node means that `extern' was
specified in its declaration. This can also be set for an
@@ -6528,7 +6531,7 @@ extern tree finish_trait_expr (enum cp
extern tree build_lambda_expr (void);
extern tree build_lambda_object (tree);
extern tree begin_lambda_type (tree);
-extern tree lambda_capture_field_type (tree, bool);
+extern tree lambda_capture_field_type (tree, bool, bool);
extern tree lambda_return_type (tree);
extern tree lambda_proxy_type (tree);
extern tree lambda_function (tree);
Index: cp/lambda.c
===================================================================
--- cp/lambda.c (revision 244054)
+++ cp/lambda.c (working copy)
@@ -211,29 +211,45 @@ lambda_function (tree lambda)
}
/* Returns the type to use for the FIELD_DECL corresponding to the
- capture of EXPR.
- The caller should add REFERENCE_TYPE for capture by reference. */
+ capture of EXPR. EXPLICIT_INIT_P indicates whether this is a
+ C++14 init capture, and BY_REFERENCE_P indicates whether we're
+ capturing by reference. */
tree
-lambda_capture_field_type (tree expr, bool explicit_init_p)
+lambda_capture_field_type (tree expr, bool explicit_init_p,
+ bool by_reference_p)
{
tree type;
bool is_this = is_this_parameter (tree_strip_nop_conversions (expr));
+
if (!is_this && type_dependent_expression_p (expr))
{
type = cxx_make_type (DECLTYPE_TYPE);
DECLTYPE_TYPE_EXPR (type) = expr;
DECLTYPE_FOR_LAMBDA_CAPTURE (type) = true;
DECLTYPE_FOR_INIT_CAPTURE (type) = explicit_init_p;
+ DECLTYPE_FOR_REF_CAPTURE (type) = by_reference_p;
SET_TYPE_STRUCTURAL_EQUALITY (type);
}
else if (!is_this && explicit_init_p)
{
- type = make_auto ();
- type = do_auto_deduction (type, expr, type);
+ tree auto_node = make_auto ();
+
+ type = auto_node;
+ if (by_reference_p)
+ /* Add the reference now, so deduction doesn't lose
+ outermost CV qualifiers of EXPR. */
+ type = build_reference_type (type);
+ type = do_auto_deduction (type, expr, auto_node);
}
else
- type = non_reference (unlowered_expr_type (expr));
+ {
+ type = non_reference (unlowered_expr_type (expr));
+
+ if (!is_this && by_reference_p)
+ type = build_reference_type (type);
+ }
+
return type;
}
@@ -504,9 +520,11 @@ add_capture (tree lambda, tree id, tree
}
else
{
- type = lambda_capture_field_type (initializer, explicit_init_p);
+ type = lambda_capture_field_type (initializer, explicit_init_p,
+ by_reference_p);
if (type == error_mark_node)
return error_mark_node;
+
if (id == this_identifier && !by_reference_p)
{
gcc_assert (POINTER_TYPE_P (type));
@@ -514,17 +532,19 @@ add_capture (tree lambda, tree id, tree
initializer = cp_build_indirect_ref (initializer, RO_NULL,
tf_warning_or_error);
}
- if (id != this_identifier && by_reference_p)
+
+ if (dependent_type_p (type))
+ ;
+ else if (id != this_identifier && by_reference_p)
{
- type = build_reference_type (type);
- if (!dependent_type_p (type) && !lvalue_p (initializer))
+ if (!lvalue_p (initializer))
error ("cannot capture %qE by reference", initializer);
}
else
{
/* Capture by copy requires a complete type. */
type = complete_type (type);
- if (!dependent_type_p (type) && !COMPLETE_TYPE_P (type))
+ if (!COMPLETE_TYPE_P (type))
{
error ("capture by copy of incomplete type %qT", type);
cxx_incomplete_type_inform (type);
Index: cp/pt.c
===================================================================
--- cp/pt.c (revision 244054)
+++ cp/pt.c (working copy)
@@ -13988,7 +13988,8 @@ tsubst (tree t, tree args, tsubst_flags_
if (DECLTYPE_FOR_LAMBDA_CAPTURE (t))
type = lambda_capture_field_type (type,
- DECLTYPE_FOR_INIT_CAPTURE (t));
+ DECLTYPE_FOR_INIT_CAPTURE (t),
+ DECLTYPE_FOR_REF_CAPTURE (t));
else if (DECLTYPE_FOR_LAMBDA_PROXY (t))
type = lambda_proxy_type (type);
else
Index: testsuite/g++.dg/cpp1y/pr66735.C
===================================================================
--- testsuite/g++.dg/cpp1y/pr66735.C (revision 0)
+++ testsuite/g++.dg/cpp1y/pr66735.C (working copy)
@@ -0,0 +1,22 @@
+// { dg-do compile { target c++14 } }
+
+// PR c++/66735, lost constness on reference capture
+
+template <typename T> void Foo ()
+{
+ T const x = 5;
+
+ auto l = [&rx = x]() {};
+
+ l ();
+}
+
+void Baz ()
+{
+ int const x = 5;
+ auto l = [&rx = x]() {};
+
+
+ l ();
+ Foo<int> ();
+}