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* [Bug libstdc++/59768] New: [4.8 Regression] std::thread constructor not handling reference_wrapper correctly
@ 2014-01-11  7:34 Casey at Carter dot net
  2014-01-11 12:58 ` [Bug libstdc++/59768] " redi at gcc dot gnu.org
                   ` (2 more replies)
  0 siblings, 3 replies; 4+ messages in thread
From: Casey at Carter dot net @ 2014-01-11  7:34 UTC (permalink / raw)
  To: gcc-bugs

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59768

            Bug ID: 59768
           Summary: [4.8 Regression] std::thread constructor not handling
                    reference_wrapper correctly
           Product: gcc
           Version: 4.8.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: Casey at Carter dot net

Created attachment 31809
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=31809&action=edit
Minimal test case.

Originally reported in Stackoverflow question
http://stackoverflow.com/questions/21059115/c11-thread-class-how-to-use-a-class-member-function

Construction of a std::thread with a pointer-to-member-function and
reference_wrapper as in this simple program:

#include <functional>
#include <iostream>
#include <thread>

class A {
public:
    void foo(int n) { std::cout << n << std::endl; }
};

int main()
{
    A a;

    std::thread t1(&A::foo, std::ref(a), 100);
    t1.join();
}

incorrectly results in a compilation error:

In file included from /usr/local/include/c++/4.8.2/thread:39:0,
                  from check.cc:2:
/usr/local/include/c++/4.8.2/functional: In instantiation of ‘struct
std::_Bind_simple<std::_Mem_fn<void (A::*)(int)>(std::reference_wrapper<A>,
int)>’:
/usr/local/include/c++/4.8.2/thread:137:47:   required from
‘std::thread::thread(_Callable&&, _Args&& ...) [with _Callable = void
(A::*)(int); _Args = {std::reference_wrapper<A>, int}]’
check.cc:13:42:   required from here
/usr/local/include/c++/4.8.2/functional:1697:61: error：no type named ‘type’ in
‘class std::result_of<std::_Mem_fn<void (A::*)(int)>(std::reference_wrapper<A>,
int)>’
        typedef typename result_of<_Callable(_Args...)>::type result_type;
                                                              ^
/usr/local/include/c++/4.8.2/functional:1727:9: error：no type named ‘type’ in
‘class std::result_of<std::_Mem_fn<void (A::*)(int)>(std::reference_wrapper<A>,
int)>’
          _M_invoke(_Index_tuple<_Indices...>)
          ^

I reduced the original program to:

#include <functional>
#include <thread>

int main() {
  struct A { void foo(int) {} } a;
  std::thread(&A::foo, std::ref(a), 100).join();
}

which still displays the erroneous behavior. Note that std::bind(&A::foo,
std::ref(a), 100) *does* compile correctly, as does a similar program in which
the member function foo has no parameter.

Program is incorrectly compiled by g++ 4.8.2 and 4.8.1, correctly compiles with
4.6.4 and 4.7.3.
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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/28865] Structures with a flexible arrray member have wrong .size
Date: Sat, 11 Jan 2014 08:14:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id(865

--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I disagree.  DECL_SIZE and .size are IMHO correct here at this point, and
component sizes (FIELD_DECL) can't match, because we shouldn't be changing the
type of the decl to some other type just because it got an initializer.  The
bug is IMHO really just in miscounting the size of the padding of the
initializer and thus emitting into the data/rodata etc. section more bytes of
data from what .size/arrays/-fsection-anchors assumes.  Outside of arrays on
non-fsection-anchors target this is just ugly (except where you e.g. put the
structs into named sections and use it as a kind of array say through
beginning/end of the named section), for -fsection-anchors it is of course a
wrong-code (well, wrong-data) bug.


^ permalink raw reply	[flat|nested] 4+ messages in thread
end of thread, other threads:[~2014-01-11 19:08 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-01-11  7:34 [Bug libstdc++/59768] New: [4.8 Regression] std::thread constructor not handling reference_wrapper correctly Casey at Carter dot net
2014-01-11 12:58 ` [Bug libstdc++/59768] " redi at gcc dot gnu.org
2014-01-11 15:36 ` Casey at Carter dot net
2014-01-11 19:08 ` [Bug libstdc++/59768] [DR 2219] " redi at gcc dot gnu.org

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