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Define feature-test macro for std::enable_shared_from_this

Message ID 20160804123307.GT4264@redhat.com
State New
Headers show

Commit Message

Jonathan Wakely Aug. 4, 2016, 12:33 p.m. UTC 
On 03/08/16 20:11 +0100, Jonathan Wakely wrote:
>Another feature we already support, so just define the macro.
>
>	* include/bits/shared_ptr_base.h (__cpp_lib_enable_shared_from_this):
>	Define feature-test macro.
>	* testsuite/20_util/enable_shared_from_this/members/reinit.cc: Test
>	for the macro.
>
>Tested x86_64-linux, committed to trunk.

I realised we don't actually implement the whole feature, because we
don't have the new weak_from_this() members (careless of me to forget
the contents of my own proposal!)

This adds them for C++17, or gnu++1*, and only defines the
feature-test macro when those members are present.

Tested powerpc64-linux, committed to trunk.
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Patch

commit 7c1f28db94c3cb1a28dba4efd0c648bc6c6bb329
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Aug 4 13:04:14 2016 +0100

    Define std::enable_shared_from_this::weak_from_this
    
    	* testsuite/20_util/enable_shared_from_this/members/reinit.cc: Use
    	effective target not dg-options. Move check for feature-test macro to:
    	* testsuite/20_util/enable_shared_from_this/members/weak_from_this.cc:
    	New test.

diff --git a/libstdc++-v3/include/bits/shared_ptr.h b/libstdc++-v3/include/bits/shared_ptr.h
index 483c2bc..747b09a 100644
--- a/libstdc++-v3/include/bits/shared_ptr.h
+++ b/libstdc++-v3/include/bits/shared_ptr.h
@@ -586,6 +586,17 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       shared_from_this() const
       { return shared_ptr<const _Tp>(this->_M_weak_this); }
 
+#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+#define __cpp_lib_enable_shared_from_this 201603
+      weak_ptr<_Tp>
+      weak_from_this()
+      { return this->_M_weak_this; }
+
+      weak_ptr<const _Tp>
+      weak_from_this() const
+      { return this->_M_weak_this; }
+#endif
+
     private:
       template<typename _Tp1>
 	void
diff --git a/libstdc++-v3/include/bits/shared_ptr_base.h b/libstdc++-v3/include/bits/shared_ptr_base.h
index 2698ba4..787dc9b 100644
--- a/libstdc++-v3/include/bits/shared_ptr_base.h
+++ b/libstdc++-v3/include/bits/shared_ptr_base.h
@@ -1472,7 +1472,6 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       void
       _M_assign(_Tp* __ptr, const __shared_count<_Lp>& __refcount) noexcept
       {
-#define __cpp_lib_enable_shared_from_this 201603
 	if (use_count() == 0)
 	  {
 	    _M_ptr = __ptr;
@@ -1557,6 +1556,16 @@  _GLIBCXX_BEGIN_NAMESPACE_VERSION
       shared_from_this() const
       { return __shared_ptr<const _Tp, _Lp>(this->_M_weak_this); }
 
+#if __cplusplus > 201402L || !defined(__STRICT_ANSI__) // c++1z or gnu++11
+      __weak_ptr<_Tp, _Lp>
+      weak_from_this()
+      { return this->_M_weak_this; }
+
+      __weak_ptr<const _Tp, _Lp>
+      weak_from_this() const
+      { return this->_M_weak_this; }
+#endif
+
     private:
       template<typename _Tp1>
 	void
diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc
index 1cf9148..3209f87 100644
--- a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/members/reinit.cc
@@ -15,15 +15,11 @@ 
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
-// { dg-options "-std=gnu++11" }
+// { dg-do run { target c++11 } }
 
 #include <memory>
 #include <testsuite_hooks.h>
 
-#if __cpp_lib_enable_shared_from_this < 201603
-# error "__cpp_lib_enable_shared_from_this < 201603"
-#endif
-
 struct X : public std::enable_shared_from_this<X> { };
 
 bool