[PATCH] Fix incorrect comment about std::auto_ptr

[Jonathan Wakely]

Pedro pointed out this comment isn't true, see LWG 463 for the reason
why (in short, it needs too many user-defined conversions).

        * include/backward/auto_ptr.h (dauto_ptr): Correct comment about
        conversions from auto_ptr<Derived> rvalues to auto_ptr<Base>.
        * testsuite/20_util/auto_ptr/assign_neg.cc: Remove redundant dg-error
        directives that only match notes, not errors.

Tested powerpc64le-linux, committed to trunk.


commit 39d4ba1f2d08632e0f860fa28b3acfe844cd219d
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Wed Oct 19 18:48:01 2016 +0100

    Fix incorrect comment about std::auto_ptr
    
        * include/backward/auto_ptr.h (dauto_ptr): Correct comment about
        conversions from auto_ptr<Derived> rvalues to auto_ptr<Base>.
        * testsuite/20_util/auto_ptr/assign_neg.cc: Remove redundant dg-error
        directives that only match notes, not errors.

diff --git a/libstdc++-v3/include/backward/auto_ptr.h 
b/libstdc++-v3/include/backward/auto_ptr.h
index bfd42d8..4dfc8cc 100644
--- a/libstdc++-v3/include/backward/auto_ptr.h
+++ b/libstdc++-v3/include/backward/auto_ptr.h
@@ -249,13 +249,17 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
       /** 
        *  @brief  Automatic conversions
        *
-       *  These operations convert an %auto_ptr into and from an auto_ptr_ref
-       *  automatically as needed.  This allows constructs such as
+       *  These operations are supposed to convert an %auto_ptr into and from
+       *  an auto_ptr_ref automatically as needed.  This would allow
+       *  constructs such as
        *  @code
        *    auto_ptr<Derived>  func_returning_auto_ptr(.....);
        *    ...
        *    auto_ptr<Base> ptr = func_returning_auto_ptr(.....);
        *  @endcode
+       *
+       *  But it doesn't work, and won't be fixed. For further details see
+       *  http://cplusplus.github.io/LWG/lwg-closed.html#463
        */
       auto_ptr(auto_ptr_ref<element_type> __ref) throw()
       : _M_ptr(__ref._M_ptr) { }
diff --git a/libstdc++-v3/testsuite/20_util/auto_ptr/assign_neg.cc 
b/libstdc++-v3/testsuite/20_util/auto_ptr/assign_neg.cc
index 5e52ec4..22cc49e 100644
--- a/libstdc++-v3/testsuite/20_util/auto_ptr/assign_neg.cc
+++ b/libstdc++-v3/testsuite/20_util/auto_ptr/assign_neg.cc
@@ -47,6 +47,3 @@ main()
   test01();
   return 0;
 }
-// { dg-error "::auto_ptr|no known conversion" "" { target *-*-* } 136 } 
-// { dg-error "note" "" { target *-*-* } 154 }
-// { dg-error "::auto_ptr|no known conversion" "" { target *-*-* } 264 }