In this testcase, instantiate_decl was trying to look up an
instantiation of a partial specialization using the arguments for the
partial specialization on the primary template, which finds a different
instance of the template. Fixed by reconstructing the arguments to the
primary template.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 18b8f994ee7c8c901a9e16d5442ec13997081d72
Author: Jason Merrill <ja...@redhat.com>
Date: Thu Jan 28 21:41:38 2016 -0500
PR c++/69009
* pt.c (partial_specialization_p, impartial_args): New.
(instantiate_decl): Call impartial_args.
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 0d0e664..27dfdf86 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -20746,6 +20746,36 @@ most_general_template (tree decl)
return decl;
}
+/* True iff the TEMPLATE_DECL tmpl is a partial specialization. */
+
+static bool
+partial_specialization_p (tree tmpl)
+{
+ /* Any specialization has DECL_TEMPLATE_SPECIALIZATION. */
+ if (!DECL_TEMPLATE_SPECIALIZATION (tmpl))
+ return false;
+ tree t = DECL_TI_TEMPLATE (tmpl);
+ /* A specialization that fully specializes one of the containing classes is
+ not a partial specialization. */
+ return (list_length (DECL_TEMPLATE_PARMS (tmpl))
+ == list_length (DECL_TEMPLATE_PARMS (t)));
+}
+
+/* If TMPL is a partial specialization, return the arguments for its primary
+ template. */
+
+static tree
+impartial_args (tree tmpl, tree args)
+{
+ if (!partial_specialization_p (tmpl))
+ return args;
+
+ /* If TMPL is a partial specialization, we need to substitute to get
+ the args for the primary template. */
+ return tsubst_template_args (DECL_TI_ARGS (tmpl), args,
+ tf_warning_or_error, tmpl);
+}
+
/* Return the most specialized of the template partial specializations
which can produce TARGET, a specialization of some class or variable
template. The value returned is actually a TREE_LIST; the TREE_VALUE is
@@ -21570,7 +21600,7 @@ instantiate_decl (tree d, int defer_ok,
return d;
gen_tmpl = most_general_template (tmpl);
- gen_args = DECL_TI_ARGS (d);
+ gen_args = impartial_args (tmpl, DECL_TI_ARGS (d));
if (tmpl != gen_tmpl)
/* We should already have the extra args. */
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ47.C b/gcc/testsuite/g++.dg/cpp1y/var-templ47.C
new file mode 100644
index 0000000..a40ec57
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ47.C
@@ -0,0 +1,19 @@
+// PR c++/69009
+// { dg-do compile { target c++14 } }
+
+using _uchar = char;
+using _size_t = decltype(sizeof(_uchar));
+using size_t = _size_t;
+template <class T, T> struct integral_constant;
+template <bool b> using bool_constant = integral_constant<bool, b>;
+template <class> constexpr auto tuple_size_v = 0;
+template <class T> auto const tuple_size_v<T const volatile> = tuple_size_v<T>;
+template <class T>
+using tuple_size = integral_constant<size_t, tuple_size_v<T>>;
+template <typename Base, typename Deriv>
+using is_base_of = bool_constant<__is_base_of(Base, Deriv)>;
+template <class T, size_t N> void test() {
+ is_base_of<integral_constant<size_t, N>, tuple_size<T>> value(
+ is_base_of<integral_constant<size_t, N>, tuple_size<const volatile T>>);
+}
+void foo() { test<int, 0>; }
