Hi,
Hi,
in this ICE on valid, a gcc_assert fires when a GOTO_EXPR is handled by
cxx_eval_constant_expression which is the translation of a "return;" on
a targetm.cxx.cdtor_returns_this target (like ARM):
;; Function constexpr A::A() (null)
;; enabled by -tree-original
{
// predicted unlikely by goto predictor.;
goto <D.4600>;
}
<D.4600>:;
return this;
I think the right way to handle this is marking such special labels with
a LABEL_DECL_CDTOR flag and using it in the returns helper function (we
already use a similar strategy with LABEL_DECL_BREAK and
LABEL_DECL_CONTINUE and the breaks and continues helpers). Then
adjusting the ICEing gcc_assert is trivial. Tested x86_64-linux and
aarch64-linux.
Thanks,
Paolo.
//////////////////////////////////
/cp
2017-09-05 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/81942
* cp-tree.h (LABEL_DECL_CDTOR): Add and document.
* decl.c (start_preparsed_function): Set LABEL_DECL_CDTOR when
creating cdtor_label.
* constexpr.c (returns): Add the case of a constructor/destructor
returning via a LABEL_DECL_CDTOR label.
(cxx_eval_constant_expression, case [GOTO_EXPR]): Likewise.
/testsuite
2017-09-05 Paolo Carlini <paolo.carl...@oracle.com>
PR c++/81942
* g++.dg/cpp1y/constexpr-return3.C: New.
Index: cp/constexpr.c
===================================================================
--- cp/constexpr.c (revision 251700)
+++ cp/constexpr.c (working copy)
@@ -3671,7 +3671,9 @@ static bool
returns (tree *jump_target)
{
return *jump_target
- && TREE_CODE (*jump_target) == RETURN_EXPR;
+ && (TREE_CODE (*jump_target) == RETURN_EXPR
+ || (TREE_CODE (*jump_target) == LABEL_DECL
+ && LABEL_DECL_CDTOR (*jump_target)));
}
static bool
@@ -4554,7 +4556,9 @@ cxx_eval_constant_expression (const constexpr_ctx
case GOTO_EXPR:
*jump_target = TREE_OPERAND (t, 0);
- gcc_assert (breaks (jump_target) || continues (jump_target));
+ gcc_assert (breaks (jump_target) || continues (jump_target)
+ /* Allow for jumping to a cdtor_label. */
+ || returns (jump_target));
break;
case LOOP_EXPR:
Index: cp/cp-tree.h
===================================================================
--- cp/cp-tree.h (revision 251700)
+++ cp/cp-tree.h (working copy)
@@ -456,6 +456,7 @@ extern GTY(()) tree cp_global_trees[CPTI_MAX];
DECL_CONSTRAINT_VAR_P (in a PARM_DECL)
TEMPLATE_DECL_COMPLEX_ALIAS_P (in TEMPLATE_DECL)
DECL_INSTANTIATING_NSDMI_P (in a FIELD_DECL)
+ LABEL_DECL_CDTOR (in LABEL_DECL)
3: DECL_IN_AGGR_P.
4: DECL_C_BIT_FIELD (in a FIELD_DECL)
DECL_ANON_UNION_VAR_P (in a VAR_DECL)
@@ -3833,6 +3834,11 @@ more_aggr_init_expr_args_p (const aggr_init_expr_a
#define LABEL_DECL_CONTINUE(NODE) \
DECL_LANG_FLAG_1 (LABEL_DECL_CHECK (NODE))
+/* Nonzero if NODE is the target for genericization of 'return' stmts
+ in constructors/destructors of targetm.cxx.cdtor_returns_this targets. */
+#define LABEL_DECL_CDTOR(NODE) \
+ DECL_LANG_FLAG_2 (LABEL_DECL_CHECK (NODE))
+
/* True if NODE was declared with auto in its return type, but it has
started compilation and so the return type might have been changed by
return type deduction; its declared return type should be found in
Index: cp/decl.c
===================================================================
--- cp/decl.c (revision 251700)
+++ cp/decl.c (working copy)
@@ -15072,7 +15073,10 @@ start_preparsed_function (tree decl1, tree attrs,
if (DECL_DESTRUCTOR_P (decl1)
|| (DECL_CONSTRUCTOR_P (decl1)
&& targetm.cxx.cdtor_returns_this ()))
- cdtor_label = create_artificial_label (input_location);
+ {
+ cdtor_label = create_artificial_label (input_location);
+ LABEL_DECL_CDTOR (cdtor_label) = true;
+ }
start_fname_decls ();
Index: testsuite/g++.dg/cpp1y/constexpr-return3.C
===================================================================
--- testsuite/g++.dg/cpp1y/constexpr-return3.C (revision 0)
+++ testsuite/g++.dg/cpp1y/constexpr-return3.C (working copy)
@@ -0,0 +1,11 @@
+// PR c++/81942
+// { dg-do compile { target c++14 } }
+
+class A {
+public:
+ constexpr A() {
+ return;
+ }
+};
+
+A mwi;
