[committed] libstdc++: Fix std::vector::emplace to forward parameter

[Jonathan Wakely]

If the parameter is not lvalue-convertible to bool then the current code
will fail to compile. The parameter should be forwarded to restore the
original value category.

libstdc++-v3/ChangeLog:

        * include/bits/stl_bvector.h (emplace_back, emplace): Forward
        parameter pack to preserve value category.
        * testsuite/23_containers/vector/bool/emplace_rvalue.cc: New
        test.
---
Tested x86_64-linux. Pushed to trunk.

 libstdc++-v3/include/bits/stl_bvector.h       |  4 ++--
 .../vector/bool/emplace_rvalue.cc             | 24 +++++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)
 create mode 100644 
libstdc++-v3/testsuite/23_containers/vector/bool/emplace_rvalue.cc

diff --git a/libstdc++-v3/include/bits/stl_bvector.h 
b/libstdc++-v3/include/bits/stl_bvector.h
index 42261ac5915..70f69b5b5b5 100644
--- a/libstdc++-v3/include/bits/stl_bvector.h
+++ b/libstdc++-v3/include/bits/stl_bvector.h
@@ -1343,7 +1343,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
 #endif
        emplace_back(_Args&&... __args)
        {
-         push_back(bool(__args...));
+         push_back(bool(std::forward<_Args>(__args)...));
 #if __cplusplus > 201402L
          return back();
 #endif
@@ -1353,7 +1353,7 @@ _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
        _GLIBCXX20_CONSTEXPR
        iterator
        emplace(const_iterator __pos, _Args&&... __args)
-       { return insert(__pos, bool(__args...)); }
+       { return insert(__pos, bool(std::forward<_Args>(__args)...)); }
 #endif
 
     protected:
diff --git a/libstdc++-v3/testsuite/23_containers/vector/bool/emplace_rvalue.cc 
b/libstdc++-v3/testsuite/23_containers/vector/bool/emplace_rvalue.cc
new file mode 100644
index 00000000000..5dea2426d60
--- /dev/null
+++ b/libstdc++-v3/testsuite/23_containers/vector/bool/emplace_rvalue.cc
@@ -0,0 +1,24 @@
+// { dg-do compile { target c++11 } }
+
+#include <vector>
+
+struct S
+{
+  explicit operator bool() &&;
+};
+
+void
+test_emplace_back()
+{
+  S s;
+  std::vector<bool> v;
+  v.emplace_back(std::move(s));
+}
+
+void
+test_emplace()
+{
+  S s;
+  std::vector<bool> v;
+  v.emplace(v.begin(), std::move(s));
+}
-- 
2.47.0