Fix PR27684 - std::tuple no longer accepts reference to incomplete type in some cases.
Libc++ has to deduce the 'allocator_arg_t' parameter as 'AllocArgT' for the
following constructor:
template <class Alloc> tuple(allocator_arg_t, Alloc const&)
Previously libc++ has tried to support tags derived from 'allocator_arg_t' by
using 'is_base_of<AllocArgT, allocator_arg_t>'. However this breaks whenever a
2-tuple contains a reference to an incomplete type as its first parameter.
See https://llvm.org/bugs/show_bug.cgi?id=27684
llvm-svn: 273334
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: 092386771dbebffbf1d2752cdaee4be577239e9b
diff --git a/include/tuple b/include/tuple
index 73f42a0..c7df34a 100644
--- a/include/tuple
+++ b/include/tuple
@@ -662,7 +662,7 @@
template <class _AllocArgT, class _Alloc, bool _Dummy = true, class = typename enable_if<
__lazy_and<
- is_base_of<allocator_arg_t, _AllocArgT>,
+ is_same<allocator_arg_t, _AllocArgT>,
__lazy_all<__dependent_type<is_default_constructible<_Tp>, _Dummy>...>
>::value
>::type>
diff --git a/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/PR27684_contains_ref_to_incomplete_type.pass.cpp b/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/PR27684_contains_ref_to_incomplete_type.pass.cpp
new file mode 100644
index 0000000..c8b722f
--- /dev/null
+++ b/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/PR27684_contains_ref_to_incomplete_type.pass.cpp
@@ -0,0 +1,51 @@
+//===----------------------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: c++98, c++03
+
+// <tuple>
+
+// template <class... Types> class tuple;
+
+// template <class Alloc> tuple(allocator_arg_t, Alloc const&)
+
+// Libc++ has to deduce the 'allocator_arg_t' parameter for this constructor
+// as 'AllocArgT'. Previously libc++ has tried to support tags derived from
+// 'allocator_arg_t' by using 'is_base_of<AllocArgT, allocator_arg_t>'.
+// However this breaks whenever a 2-tuple contains a reference to an incomplete
+// type as its first parameter. See PR27684.
+
+#include <tuple>
+#include <cassert>
+
+struct IncompleteType;
+extern IncompleteType inc1;
+extern IncompleteType inc2;
+IncompleteType const& cinc1 = inc1;
+IncompleteType const& cinc2 = inc2;
+
+int main() {
+ using IT = IncompleteType;
+ { // try calling tuple(Tp const&...)
+ using Tup = std::tuple<const IT&, const IT&>;
+ Tup t(cinc1, cinc2);
+ assert(&std::get<0>(t) == &inc1);
+ assert(&std::get<1>(t) == &inc2);
+ }
+ { // try calling tuple(Up&&...)
+ using Tup = std::tuple<const IT&, const IT&>;
+ Tup t(inc1, inc2);
+ assert(&std::get<0>(t) == &inc1);
+ assert(&std::get<1>(t) == &inc2);
+ }
+}
+
+struct IncompleteType {};
+IncompleteType inc1;
+IncompleteType inc2;
diff --git a/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/alloc.pass.cpp b/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/alloc.pass.cpp
index c69163d..4da5fc7 100644
--- a/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/alloc.pass.cpp
+++ b/test/std/utilities/tuple/tuple.tuple/tuple.cnstr/alloc.pass.cpp
@@ -7,6 +7,8 @@
//
//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03
+
// <tuple>
// template <class... Types> class tuple;
@@ -14,7 +16,9 @@
// template <class Alloc>
// tuple(allocator_arg_t, const Alloc& a);
-// UNSUPPORTED: c++98, c++03
+// NOTE: this constructor does not currently support tags derived from
+// allocator_arg_t because libc++ has to deduce the parameter as a template
+// argument. See PR27684 (https://llvm.org/bugs/show_bug.cgi?id=27684)
#include <tuple>
#include <cassert>
@@ -42,10 +46,6 @@
std::tuple<> t(std::allocator_arg, A1<int>());
}
{
- DerivedFromAllocArgT tag;
- std::tuple<> t(tag, A1<int>());
- }
- {
std::tuple<int> t(std::allocator_arg, A1<int>());
assert(std::get<0>(t) == 0);
}
@@ -95,21 +95,6 @@
assert(std::get<2>(t) == alloc_last());
}
{
- // Test that allocator construction is selected when the user provides
- // a custom tag type which derives from allocator_arg_t.
- DerivedFromAllocArgT tag;
- alloc_first::allocator_constructed = false;
- alloc_last::allocator_constructed = false;
-
- std::tuple<DefaultOnly, alloc_first, alloc_last> t(tag, A1<int>(5));
-
- assert(std::get<0>(t) == DefaultOnly());
- assert(alloc_first::allocator_constructed);
- assert(std::get<1>(t) == alloc_first());
- assert(alloc_last::allocator_constructed);
- assert(std::get<2>(t) == alloc_last());
- }
- {
// Test that the uses-allocator default constructor does not evaluate
// it's SFINAE when it otherwise shouldn't be selected. Do this by
// using 'NonDefaultConstructible' which will cause a compile error