[PATCH] PR c++/67054 Allow inheriting constructor with non-default-constructible members

[Leonid Koppel]

This patch addresses PR 67054 (duplicates 62310, 80851). An implicitly-defined 
inheriting constructor was wrongly considered deleted when it would initialize 
a non-default-constructible member, even when a brace-or-equal-initializer was 
present.

The bug only affects deduction of the constructor's deletedness, not the actual 
generation of the constructor, which is why (I hope!) the fix might be so 
simple.

Tested on x86_64-pc-linux-gnu native.

Thanks,
Leo

2017-07-26  Leonid Koppel  <lkop...@uwaterloo.ca>

        PR c++/67054 - Inheriting constructor with non-default-constructible 
members
        * method.c (walk_field_subobs) Consider member initializers (NSDMIs) 
when 
        deducing an inheriting constructor.

diff --git a/gcc/cp/method.c b/gcc/cp/method.c
index cca1b146917..8b07f526473 100644
--- a/gcc/cp/method.c
+++ b/gcc/cp/method.c
@@ -1342,7 +1342,7 @@ walk_field_subobs (tree fields, tree fnname, 
special_function_kind sfk,
          if (bad && deleted_p)
            *deleted_p = true;
        }
-      else if (sfk == sfk_constructor)
+      else if (sfk == sfk_constructor || sfk == sfk_inheriting_constructor)
        {
          bool bad;
 
diff --git a/gcc/testsuite/g++.dg/cpp0x/inh-ctor29.C 
b/gcc/testsuite/g++.dg/cpp0x/inh-ctor29.C
new file mode 100644
index 00000000000..8e31f739d74
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/inh-ctor29.C
@@ -0,0 +1,23 @@
+// PR c++/67054
+// { dg-do compile { target c++11 } }
+
+struct A
+{
+  A(int) {}
+};
+
+struct C
+{
+  C(int) {}
+};
+
+struct B : A
+{
+  using A::A;
+  C c = 42;
+};
+
+int main()
+{
+  B b = 24;
+}