In this case, when we see the explicit template arguments for test and
go to substitute them into the type of sfinae_base::test, we were
recording that we wanted to check access to sfinae_base::make in the
context of is_printable, but then by the time we got around to checking
it we had pushed into the context of sfinae_base which doesn't have the
right to see make by way of is_printable. Fixed by discarding any
deferred access checks from explicit template argument substitution,
because we'll get the same access checks when we substitute in all the
template arguments in instantiate_template, and those will have the
right access path.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit a194a47d7bc3bbdc362ba78cbb30fc493b9a3fdb
Author: Jason Merrill <ja...@redhat.com>
Date: Tue Feb 5 14:01:41 2013 -0500
PR c++/56208
* pt.c (fn_type_unification): Discard any access checks from
substituting explicit args.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 7430289..aa127ed 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -14989,6 +14989,12 @@ fn_type_unification (tree fn,
if (fntype == error_mark_node)
goto fail;
+ /* Throw away these access checks; we'll see them again in
+ instantiate_template and they might have the wrong
+ access path at this point. */
+ pop_deferring_access_checks ();
+ push_deferring_access_checks (dk_deferred);
+
/* Place the explicitly specified arguments in TARGS. */
for (i = NUM_TMPL_ARGS (explicit_targs); i--;)
TREE_VEC_ELT (targs, i) = TREE_VEC_ELT (explicit_targs, i);
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae43.C b/gcc/testsuite/g++.dg/cpp0x/sfinae43.C
new file mode 100644
index 0000000..22efe65
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae43.C
@@ -0,0 +1,31 @@
+// PR c++/56208
+// { dg-options -std=c++11 }
+
+struct ostream {
+ ostream& operator<<(int);
+};
+
+struct sfinae_base {
+
+ typedef char one;
+ typedef char (&two)[2];
+
+ template<class T>
+ static T make();
+
+ template<unsigned> struct ok { typedef int type; };
+
+ template<class U, class T>
+ static one test(decltype((make<U>() << make<T>()), 0));
+
+ template<class, class>
+ static two test(...);
+};
+
+template<class T>
+struct is_printable : private sfinae_base
+{
+ enum { value = sizeof(test<ostream&, T>(0)) == sizeof(one) };
+};
+
+typedef int ok[is_printable<int>::value ? 1 : -1];