[GHC] #9684: Broken build on OS X (incompatible pthread_setname_np API)

12 Oct 2014

      #9684: Broken build on OS X (incompatible pthread_setname_np API)
-------------------------------------+-------------------------------------
       Reporter:  mlen               |                   Owner:
           Type:  bug                |                  Status:  new
       Priority:  normal             |               Milestone:
      Component:  Compiler           |                 Version:  7.9
       Keywords:                     |        Operating System:  MacOS X
  pthread_setname_np                 |         Type of failure:  Building
   Architecture:  Unknown/Multiple   |  GHC failed
     Difficulty:  Unknown            |               Test Case:
     Blocked By:                     |                Blocking:
Related Tickets:                     |  Differential Revisions:
                                     |  674c631ea111233daa929ef63500d75ba0db8858
-------------------------------------+-------------------------------------
 Build is broken on OS X because it is only possible to set thread name for
 the current thread and `pthread_setname_np` accepts a single argument.
 This function appeared in 10.6. If that OS version needs to be supported,
 the best thing that can be done is conditional compilation. A short
 summary of inconsistencies between different *nix systems can be found
 here: http://stackoverflow.com/questions/2369738/can-i-set-the-name-of-a
 -thread-in-pthreads-linux/7989973#7989973

 The error log:
 {{{
 rts/posix/OSThreads.c:138:30:
      error: too many arguments to function call, expected 1, have 2
         pthread_setname_np(*pId, name);
         ~~~~~~~~~~~~~~~~~~       ^~~~

 /usr/include/pthread.h:471:1:
      note: 'pthread_setname_np' declared here
 __OSX_AVAILABLE_STARTING(__MAC_10_6, __IPHONE_3_2)
 ^

 /usr/include/Availability.h:159:50:
      note: expanded from macro '__OSX_AVAILABLE_STARTING'
         #define __OSX_AVAILABLE_STARTING(_osx, _ios)
 __AVAILABILITY_INTERNAL##_osx
                                                      ^

 <scratch space>:65:1:  note: expanded from here
 __AVAILABILITY_INTERNAL__MAC_10_6
 ^

 /usr/include/AvailabilityInternal.h:3912:72:
      note: expanded from macro '__AVAILABILITY_INTERNAL__MAC_10_6'
                 #define __AVAILABILITY_INTERNAL__MAC_10_6
 __attribute__((availability(macosx,introduced=10.6)))
 ^
 1 error generated.
 }}}

 I can see two possible solutions for OS X:
 1. disable setting thread name by conditional compilation.
 2. write some trampoline code to work around the fact that it is only
 possible to set thread name for the current thread.

 The latter would look like this:
 {{{
 struct wrapper {
     char *name;
     void *param;
     void *(*cont)(void *);
 };

 void *trampoline(void *ctx) {
   struct wrapper *params = (struct wrapper *)ctx;
   void *param = params->param;
   void *(*cont)(void *) = params->cont;

 #ifdef MACOSX
   pthread_setname_np(params->name);
 #elif
   pthread_setname_np(pthread_self(), params->name);
 #endif
   free(params);

   return cont(param);
 }

 int
 createOSThread (OSThreadId* pId, char *name,
                 OSThreadProc *startProc, void *param)
 {
   struct wrapper *ctx = malloc(sizeof(struct wrapper));

   ctx->name = name;
   ctx->cont = startProc;
   ctx->param = param;

   int result = pthread_create(pId, NULL, (void *(*)(void *))trampoline,
 &ctx);
   if (!result) {
     pthread_detach(*pId);
   } else {
     free(ctx);
   }
   return result;
 }
 }}}

 It looks very hackish and I think it'd be better to go with (1), since the
 original change was made for debugging purposes.

--
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/9684
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