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PR78991 make __gnu_cxx::__ops constructors explicit

Message ID 20170109110457.GE13348@redhat.com
State New
Headers show

Commit Message

Jonathan Wakely Jan. 9, 2017, 11:04 a.m. UTC 
On 09/01/17 10:47 +0000, Jonathan Wakely wrote:
>On 09/01/17 10:39 +0000, Kyrill Tkachov wrote:

>>Hi Jonathan,

>>

>>On 06/01/17 12:40, Jonathan Wakely wrote:

>>>This solves a problem when using libstdc++ with Clang, due to Clang

>>>more eagerly instantiating constexpr function templates during

>>>argument deduction. G++ has some shortcuts to avoid this problem, but

>>>Clang doesn't, and it's not clear that it's strictly speaking a bug in

>>>Clang or if it's following the standard. By making these constructors

>>>explicit we stop them being considered by overload resolution for

>>>copying these functors, which stops us ending up back in the

>>>std::function SFINAE checks.

>>>

>>>I'm also using _GLIBCXX_MOVE to turn some internal copies into moves,

>>>because otherwise using something like std::function with <algorithm>

>>>results in a number of potentially expensive copies.

>>>

>>>   PR libstdc++/78991

>>>   * include/bits/predefined_ops.h (_Iter_comp_iter, _Iter_comp_val)

>>>   (_Val_comp_iter, _Iter_equals_val, _Iter_pred, _Iter_comp_to_val)

>>>   (_Iter_comp_to_iter, _Iter_negate): Make constructors explicit and

>>>   move function objects.

>>>   (__iter_comp_iter, __iter_comp_val, __val_comp_iter, __pred_iter)

>>>   (__iter_comp_val, __iter_comp_iter, __negate): Move function objects.

>>>   * testsuite/25_algorithms/sort/78991.cc: New test.

>>>

>>>Tested powerpc64le-linux, committed to trunk.

>>>

>>>I'll backport  the 'explicit' constructors (but not the _GLIBCXX_MOVE

>>>changes) to the branches too.

>>>

>>

>>I see this test fail on the GCC 5 branch on arm and aarch64 (error message pasted below).

>>Does the test need a gnu++11 guard or something on the branch?

>

>I thought I'd changed that before committing, I'll fix it.


Committed to gcc-5-branch.
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Patch

commit 366c9e60ffa0536ab87de4e70ec807c2eb5fb66b
Author: Jonathan Wakely <jwakely@redhat.com>
Date:   Mon Jan 9 10:54:44 2017 +0000

    Add missing dg-options to C++14 test
    
    	* testsuite/25_algorithms/sort/78991.cc: Compile with -std=gnu++14.

diff --git a/libstdc++-v3/testsuite/25_algorithms/sort/78991.cc b/libstdc++-v3/testsuite/25_algorithms/sort/78991.cc
index d947538..260878e 100644
--- a/libstdc++-v3/testsuite/25_algorithms/sort/78991.cc
+++ b/libstdc++-v3/testsuite/25_algorithms/sort/78991.cc
@@ -15,6 +15,7 @@ 
 // with this library; see the file COPYING3.  If not see
 // <http://www.gnu.org/licenses/>.
 
+// { dg-options "-std=gnu++14" }
 // { dg-do compile }
 
 // PR 78991