Re: [v3 patch] Fix self-assignment in std::experimental::any

[Jonathan Wakely <jwakely at redhat dot com>]

On 30/07/15 11:00 +0100, Jonathan Wakely wrote:
> When I fixed any's copying of non-trivial types I broke the
> self-assignment case. This adds an explicit check for it.
>
> Thanks to Axel Menzel for noticing the bug.

Similar checks in move-assign and swap members, and a better test.

Tested powerpc64le-linux, committed to trunk.

commit d1f50d92b49bec8849bdfd6ea56fbfd1480c5edf
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Fri Aug 14 10:45:19 2015 +0100

    	* include/experimental/any (any::operator=(const any&)): Move check
    	for self-assignment.
    	(any::operator=(any&&)): Add check for self-assignment.
    	(any::operator=(_ValueType&&)): Constrain template argument.
    	(any::swap(any&)): Add check for self-swap.
    	* testsuite/experimental/any/assign/self.cc: Test move and swap.
    	* testsuite/experimental/any/misc/any_cast_neg.cc: Update dg-error.

diff --git a/libstdc++-v3/include/experimental/any b/libstdc++-v3/include/experimental/any
index fbb70a7..dae82b5 100644
--- a/libstdc++-v3/include/experimental/any
+++ b/libstdc++-v3/include/experimental/any
@@ -175,12 +175,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     /// Copy the state of another object.
     any& operator=(const any& __rhs)
     {
-      if (this == &__rhs)
-	return *this;
-
       if (__rhs.empty())
 	clear();
-      else
+      else if (this != &__rhs)
 	{
 	  if (!empty())
 	    _M_manager(_Op_destroy, this, nullptr);
@@ -200,7 +197,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     {
       if (__rhs.empty())
 	clear();
-      else
+      else if (this != &__rhs)
 	{
 	  if (!empty())
 	    _M_manager(_Op_destroy, this, nullptr);
@@ -213,7 +210,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
     /// Store a copy of @p __rhs as the contained object.
     template<typename _ValueType>
-      any& operator=(_ValueType&& __rhs)
+      enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&>
+      operator=(_ValueType&& __rhs)
       {
 	*this = any(std::forward<_ValueType>(__rhs));
 	return *this;
@@ -233,30 +231,33 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
 
     /// Exchange state with another object.
     void swap(any& __rhs) noexcept
-      {
-	if (empty() && __rhs.empty())
-	  return;
+    {
+      if (empty() && __rhs.empty())
+	return;
 
-	if (!empty() && !__rhs.empty())
-	  {
-	    any __tmp;
-	    _Arg __arg;
-	    __arg._M_any = &__tmp;
-	    __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
-	    __arg._M_any = &__rhs;
-	    _M_manager(_Op_xfer, this, &__arg);
-	    __arg._M_any = this;
-	    __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
-	  }
-	else
-	  {
-	    any* __empty = empty() ? this : &__rhs;
-	    any* __full = empty() ? &__rhs : this;
-	    _Arg __arg;
-	    __arg._M_any = __empty;
-	    __full->_M_manager(_Op_xfer, __full, &__arg);
-	  }
-      }
+      if (!empty() && !__rhs.empty())
+	{
+	  if (this == &__rhs)
+	    return;
+
+	  any __tmp;
+	  _Arg __arg;
+	  __arg._M_any = &__tmp;
+	  __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
+	  __arg._M_any = &__rhs;
+	  _M_manager(_Op_xfer, this, &__arg);
+	  __arg._M_any = this;
+	  __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
+	}
+      else
+	{
+	  any* __empty = empty() ? this : &__rhs;
+	  any* __full = empty() ? &__rhs : this;
+	  _Arg __arg;
+	  __arg._M_any = __empty;
+	  __full->_M_manager(_Op_xfer, __full, &__arg);
+	}
+    }
 
     // observers
 
diff --git a/libstdc++-v3/testsuite/experimental/any/assign/self.cc b/libstdc++-v3/testsuite/experimental/any/assign/self.cc
index 0fb9566..79c6f0f 100644
--- a/libstdc++-v3/testsuite/experimental/any/assign/self.cc
+++ b/libstdc++-v3/testsuite/experimental/any/assign/self.cc
@@ -18,8 +18,17 @@
 // { dg-options "-std=gnu++14" }
 
 #include <experimental/any>
+#include <set>
 #include <testsuite_hooks.h>
 
+std::set<const void*> live_objects;
+
+struct A {
+  A() { live_objects.insert(this); }
+  ~A() { live_objects.erase(this); }
+  A(const A& a) { VERIFY(live_objects.count(&a)); live_objects.insert(this); }
+};
+
 void
 test01()
 {
@@ -29,13 +38,56 @@ test01()
   a = a;
   VERIFY( a.empty() );
 
-  a = 1;
+  a = A{};
   a = a;
   VERIFY( !a.empty() );
+
+  a.clear();
+  VERIFY( live_objects.empty() );
+}
+
+void
+test02()
+{
+  using std::experimental::any;
+
+  struct X {
+    any a;
+  };
+
+  X x;
+  std::swap(x, x); // results in "self-move-assignment" of X::a
+  VERIFY( x.a.empty() );
+
+  x.a = A{};
+  std::swap(x, x); // results in "self-move-assignment" of X::a
+  VERIFY( !x.a.empty() );
+
+  x.a.clear();
+  VERIFY( live_objects.empty() );
+}
+
+void
+test03()
+{
+  using std::experimental::any;
+
+  any a;
+  a.swap(a);
+  VERIFY( a.empty() );
+
+  a = A{};
+  a.swap(a);
+  VERIFY( !a.empty() );
+
+  a.clear();
+  VERIFY( live_objects.empty() );
 }
 
 int
 main()
 {
   test01();
+  test02();
+  test03();
 }
diff --git a/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc b/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc
index b88592a..1d1180c 100644
--- a/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc
+++ b/libstdc++-v3/testsuite/experimental/any/misc/any_cast_neg.cc
@@ -26,5 +26,5 @@ void test01()
   using std::experimental::any_cast;
 
   const any y(1);
-  any_cast<int&>(y); // { dg-error "qualifiers" "" { target { *-*-* } } 359 }
+  any_cast<int&>(y); // { dg-error "qualifiers" "" { target { *-*-* } } 360 }
 }