[Bug libstdc++/52681] New: [C++11] Using std::thread without -pthread crashes without warning

[Bug libstdc++/52681] New: [C++11] Using std::thread without -pthread crashes without warning

[mkline at cs dot wisc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

             Bug #: 52681
           Summary: [C++11] Using std::thread without -pthread crashes
                    without warning
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: mkline@cs.wisc.edu


Without -pthread, the constructor of std::thread always throws
std::system_error. While this was apparently the resolution to bug 42198,
simply throwing an error with the code 'operation_not_permitted' is rather
mystifying to someone who isn't aware of the problem in the first place.

Would it be possible to offer a more descriptive error, preferably at compile
time?

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Severity|minor                       |enhancement

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-03-23 12:31:38 UTC ---
The problem is that not all targets need -pthread, or some which do need it
spell it differently, and not all platforms define _REENTRANT when the option
is used, so there's no reliable way to do what you're asking for.

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[mkline at cs dot wisc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

--- Comment #2 from Matt Kline <mkline at cs dot wisc.edu> 2012-03-23 13:16:23 UTC ---
Would it be possible to at least make the exception that is being thrown more
descriptive? I had guessed that some kind of compile-time warning might be
impossible, but my main concern is that the exception that gets thrown offers
little insight on what the problem might be.

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2012-03-23 13:29:38 UTC ---
Probably, something in the docs could be also useful.

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |ASSIGNED
   Last reconfirmed|                            |2012-04-18
         AssignedTo|unassigned at gcc dot       |redi at gcc dot gnu.org
                   |gnu.org                     |
     Ever Confirmed|0                           |1

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-04-18 10:05:43 UTC ---
We could fix this just by overloading __throw_system_error to take a string:

 __throw_system_error(int(errc::operation_not_permitted),
                      "Enable multithreading support to use std::thread");

then passing that to the std::system_error constructor.

That would give something like:

terminate called after throwing an instance of 'std::system_error'
  what():  Enable multithreading support to use std::thread: Operation not
permitted
Aborted (core dumped)

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[mkline at cs dot wisc.edu]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

--- Comment #5 from Matt Kline <mkline at cs dot wisc.edu> 2012-04-18 14:04:37 UTC ---
That, if feasible, would be perfect.

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-04-18 14:16:20 UTC ---
Entirely feasible, and probably safe enough for the 4.6 and 4.7 branches too.

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-08-12 18:57:58 UTC ---
Author: redi
Date: Sun Aug 12 18:57:53 2012
New Revision: 190330

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=190330
Log:
    PR libstdc++/52681
    * src/c++11/thread.cc (thread::_M_start_thread): Improve error text
    when threads are not enabled.

Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/src/c++11/thread.cc

[Bug libstdc++/52681] [C++11] Using std::thread without -pthread crashes without warning

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52681

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|---                         |4.8.0

--- Comment #8 from Jonathan Wakely <redi at gcc dot gnu.org> 2012-08-12 19:02:45 UTC ---
fixed for 4.8