Bug 78495 is a wrong code bug caused by an invisiref parm. When
building the inherited ctor, we use forward_parm to create a forwarding
reference. That code generation considers the type of the parm to be
'T'. We thus end up with a tree that looks like *&PARM
The subsequent call gets 'CALL_FROM_THUNK' set. We need that set so
code generation doesn't copy pass-by-invisiref objects that are
specified by the C abi (but not specified so by the C++ abi) (POD
structs, commonly).
cp_genericize is used to mutate invisiref parm_decls from T to &T and
bash their uses from PARM to *PARM (with suitable checking of &PARM
turning into plain PARM). However it explicitly skips genericizing the
args of a CALL_FROM_THUNK tree. Thus we end up taking the address of the
reference parm itself.
That appears to be incorrect now we have forward_parm. This patch
deletes that skipping.
ok?
nathan
--
Nathan Sidwell
2017-01-20 Nathan Sidwell <nat...@acm.org>
PR c++/78495 - wrong code inherited ctor and invisi-ref parm
* cp-gimplify.c (cp_generize_r): Don't skip thunks.
PR c++/79495
* g++.dg/cpp1z/inh-ctor38.C: New.
Index: cp/cp-gimplify.c
===================================================================
--- cp/cp-gimplify.c (revision 244596)
+++ cp/cp-gimplify.c (working copy)
@@ -1103,15 +1103,7 @@ cp_genericize_r (tree *stmt_p, int *walk
&& omp_var_to_track (stmt))
omp_cxx_notice_variable (wtd->omp_ctx, stmt);
- /* Don't dereference parms in a thunk, pass the references through. */
- if ((TREE_CODE (stmt) == CALL_EXPR && CALL_FROM_THUNK_P (stmt))
- || (TREE_CODE (stmt) == AGGR_INIT_EXPR && AGGR_INIT_FROM_THUNK_P (stmt)))
- {
- *walk_subtrees = 0;
- return NULL;
- }
-
- /* Otherwise, do dereference invisible reference parms. */
+ /* Dereference invisible reference parms. */
if (wtd->handle_invisiref_parm_p && is_invisiref_parm (stmt))
{
*stmt_p = convert_from_reference (stmt);
Index: testsuite/g++.dg/cpp1z/inh-ctor38.C
===================================================================
--- testsuite/g++.dg/cpp1z/inh-ctor38.C (revision 0)
+++ testsuite/g++.dg/cpp1z/inh-ctor38.C (working copy)
@@ -0,0 +1,31 @@
+// { dg-do run { target c++11 } }
+// PR78495 failed to propagate pass-by-value struct to base ctor.
+
+struct Ptr {
+ void *ptr = 0;
+
+ Ptr() {}
+ Ptr(Ptr const&) = delete;
+ Ptr(Ptr&& other) : ptr (other.ptr) {}
+};
+
+struct Base {
+ Ptr val;
+ Base(Ptr val_) : val(static_cast<Ptr&&>(val_)) {}
+};
+
+struct Derived: Base {
+ using Base::Base;
+};
+
+void *Foo () {
+ Ptr ptr;
+
+ Derived d(static_cast<Ptr&&>(ptr));
+
+ return d.val.ptr;
+}
+
+int main () {
+ return Foo () != 0;
+}
