Re: [PATCH] Make std::enable_shared_from_this cope with ambiguity

[Jonathan Wakely <jwakely at redhat dot com>]

On 19/10/16 21:13 +0100, Jonathan Wakely wrote:
> The standard says we have to enable shared_from_this for types with
> an accessible and unambiguous std::enable_shared_from_this base
> class, and we should be able to do that even if the class also has
> an experimental::enable_shared_from_this base class. Now we can.

This adds some more checks for that case.

Tested x86_64-linux, committed to trunk.


commit ad6e844e7d0a30a5cb53044d6147f291f9d70378
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Thu Oct 20 01:00:16 2016 +0100

    Add more tests for enable_shared_from_this ambiguities
    
    	* testsuite/20_util/enable_shared_from_this/56383.cc: Add tests for
    	additional ambiguous cases.

diff --git a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc
index fb3fa69..9220eaf 100644
--- a/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc
+++ b/libstdc++-v3/testsuite/20_util/enable_shared_from_this/56383.cc
@@ -20,37 +20,66 @@
 #include <memory>
 #include <testsuite_hooks.h>
 
-struct A : std::enable_shared_from_this<A>
+template<typename T>
+bool not_enabled(T& t)
 {
-    void* a() { return shared_from_this().get(); }
-};
+#if __cpp_lib_enable_shared_from_this >= 201603
+  return t.weak_from_this().expired();
+#else
+  try {
+    t.shared_from_this();
+    return false;
+  } catch (const std::bad_weak_ptr&) {
+    return true;
+  }
+#endif
+}
 
-struct B : std::enable_shared_from_this<B>
-{
-};
-
-struct D : A, B
-{
-};
+struct A : std::enable_shared_from_this<A> { };
+struct B : std::enable_shared_from_this<B> { };
+struct D : A, B { };
 
 void test01()
 {
-  bool test = false;
-
   auto d = std::make_shared<D>();
-  try
-  {
-      d->a();
-  }
-  catch (const std::bad_weak_ptr&)
-  {
-    test = true;
-  }
-  VERIFY(test);
+  VERIFY( not_enabled( static_cast<A&>(*d) ) );
+  VERIFY( not_enabled( static_cast<const A&>(*d) ) );
+  VERIFY( not_enabled( static_cast<B&>(*d) ) );
+  VERIFY( not_enabled( static_cast<const B&>(*d) ) );
+}
+
+struct E : std::__enable_shared_from_this<E> { };
+struct F : std::__enable_shared_from_this<F> { };
+struct G : E, F { };
+
+void test02()
+{
+  auto g = std::make_shared<G>();
+  VERIFY( not_enabled( static_cast<E&>(*g) ) );
+  VERIFY( not_enabled( static_cast<const E&>(*g) ) );
+  VERIFY( not_enabled( static_cast<F&>(*g) ) );
+  VERIFY( not_enabled( static_cast<const F&>(*g) ) );
+}
+
+struct H : D, G { };
+
+void test03()
+{
+  auto h = std::make_shared<H>();
+  VERIFY( not_enabled( static_cast<A&>(*h) ) );
+  VERIFY( not_enabled( static_cast<const A&>(*h) ) );
+  VERIFY( not_enabled( static_cast<B&>(*h) ) );
+  VERIFY( not_enabled( static_cast<const B&>(*h) ) );
+  VERIFY( not_enabled( static_cast<E&>(*h) ) );
+  VERIFY( not_enabled( static_cast<const E&>(*h) ) );
+  VERIFY( not_enabled( static_cast<F&>(*h) ) );
+  VERIFY( not_enabled( static_cast<const F&>(*h) ) );
 }
 
 int
 main()
 {
   test01();
+  test02();
+  test03();
 }