On Wed, Jan 11, 2017 at 10:53 AM, Nathan Sidwell <nat...@acm.org> wrote:
> On 01/04/2017 12:53 AM, Jason Merrill wrote:
>
>> Hmm, that seems like where the problem is. We shouldn't try to
>> instantiate the inheriting constructor until we've already chosen the
>> base constructor; in the new model the inheriting constructor is just an
>> implementation detail.
>
> Oh what fun. This testcase behaves differently for C++17, C++11
> -fnew-inheriting-ctors and C++11 -fno-new-inheriting-ctors compilation
> modes.
>
> Firstly, unpatched G++ is fine in C++17 mode, because:
> /* In C++17, "If the initializer expression is a prvalue and the
> cv-unqualified version of the source type is the same class as the
> class
> of the destination, the initializer expression is used to initialize
> the
> destination object." Handle that here to avoid doing overload
> resolution. */
> and inside that we have:
>
> /* FIXME P0135 doesn't say how to handle direct initialization from a
> type with a suitable conversion operator. Let's handle it like
> copy-initialization, but allowing explict conversions. */
>
> That conversion lookup short-circuits the subsequent overload resolution
> that would otherwise explode.
>
> Otherwise, with -fnew-inheriting-ctors, you are indeed correct. There needs
> to be a call to strip_inheriting_ctors in deduce_inheriting_ctor.
That doesn't seem quite right; in deducing the inheriting ctor we are
interested in what it actually calls, so we don't want to strip. I
was thinking about changing when we do that deduction: we shouldn't be
calling deduce_inheriting_ctor until we actually know we're calling
this inheriting ctor. I was thinking that would mean removing the
code in fn_type_unification with the comment
/* After doing deduction with the inherited constructor, actually
return an
instantiation of the inheriting constructor. */
and then looking up the inheriting constructor somehow in
build_over_call. But that gets to be a big change.
Something smaller would be moving the call to deduce_inheriting_ctor
to build_over_call; we can get away with that because calling is the
only way to refer to a constructor. What do you think of this
approach?
commit 56586a488a27f2d5b502bd35aaec7225d0fb1d31
Author: Jason Merrill <ja...@redhat.com>
Date: Wed Jan 25 16:52:28 2017 -0500
deduce-late
diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index a78e1a9..99c51f3 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -7581,6 +7581,11 @@ build_over_call (struct z_candidate *cand, int flags,
tsubst_flags_t complain)
joust (cand, w->loser, 1, complain);
}
+ /* OK, we're actually calling this inherited constructor; set its deletedness
+ appropriately. */
+ if (DECL_INHERITED_CTOR (fn))
+ deduce_inheriting_ctor (fn);
+
/* Make =delete work with SFINAE. */
if (DECL_DELETED_FN (fn) && !(complain & tf_error))
return error_mark_node;
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index b7c26a1..03a9730 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -1197,8 +1197,6 @@ add_method (tree type, tree method, tree using_decl)
SET_DECL_INHERITED_CTOR
(fn, ovl_cons (DECL_INHERITED_CTOR (method),
DECL_INHERITED_CTOR (fn)));
- /* Adjust deletedness and such. */
- deduce_inheriting_ctor (fn);
/* And discard the new one. */
return false;
}
diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index 5b366f0..e80b806 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -1855,6 +1855,7 @@ explain_implicit_non_constexpr (tree decl)
void
deduce_inheriting_ctor (tree decl)
{
+ decl = DECL_ORIGIN (decl);
gcc_assert (DECL_INHERITED_CTOR (decl));
tree spec;
bool trivial, constexpr_, deleted;
@@ -1868,6 +1869,13 @@ deduce_inheriting_ctor (tree decl)
deleted = true;
DECL_DELETED_FN (decl) = deleted;
TREE_TYPE (decl) = build_exception_variant (TREE_TYPE (decl), spec);
+
+ tree clone;
+ FOR_EACH_CLONE (clone, decl)
+ {
+ DECL_DELETED_FN (clone) = deleted;
+ TREE_TYPE (clone) = build_exception_variant (TREE_TYPE (clone), spec);
+ }
}
/* Implicitly declare the special function indicated by KIND, as a
@@ -1968,10 +1976,10 @@ implicitly_declare_fn (special_function_kind kind, tree
type,
bool trivial_p = false;
- if (inherited_ctor && TREE_CODE (inherited_ctor) == TEMPLATE_DECL)
+ if (inherited_ctor)
{
- /* For an inheriting constructor template, just copy these flags from
- the inherited constructor template for now. */
+ /* For an inheriting constructor, just copy these flags from the
+ inherited constructor until deduce_inheriting_ctor. */
raises = TYPE_RAISES_EXCEPTIONS (TREE_TYPE (inherited_ctor));
deleted_p = DECL_DELETED_FN (inherited_ctor);
constexpr_p = DECL_DECLARED_CONSTEXPR_P (inherited_ctor);
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 537d107..c96ceed 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -12358,8 +12358,6 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain)
maybe_retrofit_in_chrg (r);
if (DECL_CONSTRUCTOR_P (r))
grok_ctor_properties (ctx, r);
- if (DECL_INHERITED_CTOR (r))
- deduce_inheriting_ctor (r);
/* If this is an instantiation of a member template, clone it.
If it isn't, that'll be handled by
clone_constructors_and_destructors. */
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr78771-new.C
b/gcc/testsuite/g++.dg/cpp0x/pr78771-new.C
new file mode 100644
index 0000000..f489f86
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr78771-new.C
@@ -0,0 +1,28 @@
+// PR c++/78771
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-fnew-inheriting-ctors" }
+
+// ICE instantiating a deleted inherited ctor
+
+struct Base
+{
+ template <typename U> Base (U);
+
+ Base (int);
+};
+
+struct Derived;
+
+struct Middle : Base
+{
+ using Base::Base;
+
+ Middle (Derived);
+};
+
+struct Derived : Middle
+{
+ using Middle::Middle;
+};
+
+Middle::Middle (Derived) : Middle (0) {}
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr78771-old.C
b/gcc/testsuite/g++.dg/cpp0x/pr78771-old.C
new file mode 100644
index 0000000..b723b11
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr78771-old.C
@@ -0,0 +1,28 @@
+// PR c++/78771
+// { dg-do compile { target c++11 } }
+// { dg-additional-options "-fno-new-inheriting-ctors" }
+
+// ICE instantiating a deleted inherited ctor
+
+struct Base
+{
+ template <typename U> Base (U);
+
+ Base (int);
+};
+
+struct Derived;
+
+struct Middle : Base
+{
+ using Base::Base;
+
+ Middle (Derived);
+};
+
+struct Derived : Middle
+{
+ using Middle::Middle;
+};
+
+Middle::Middle (Derived) : Middle (0) {}
diff --git a/gcc/testsuite/g++.dg/cpp1z/pr78771.C
b/gcc/testsuite/g++.dg/cpp1z/pr78771.C
new file mode 100644
index 0000000..9178494
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/pr78771.C
@@ -0,0 +1,27 @@
+// PR c++/78771
+// { dg-options -std=c++1z }
+
+// ICE instantiating a deleted inherited ctor
+
+struct Base
+{
+ template <typename U> Base (U);
+
+ Base (int);
+};
+
+struct Derived;
+
+struct Middle : Base
+{
+ using Base::Base;
+
+ Middle (Derived);
+};
+
+struct Derived : Middle
+{
+ using Middle::Middle;
+};
+
+Middle::Middle (Derived) : Middle (0) {}
