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       pthread_getattr_default_np,  pthread_setattr_default_np,  -  get  or  set  default thread-
       creation attributes


       #define _GNU_SOURCE             /* See feature_test_macros(7) */
       #include <pthread.h>

       int pthread_getattr_default_np(pthread_attr_t *attr);
       int pthread_setattr_default_np(pthread_attr_t *attr);

       Compile and link with -pthread.


       The pthread_setattr_default_np() function sets the default attributes used for creation of
       a new thread—that is, the attributes that are used when pthread_create(3) is called with a
       second argument that is NULL.   The  default  attributes  are  set  using  the  attributes
       supplied  in *attr, a previously initialized thread attributes object.  Note the following
       details about the supplied attributes object:

       *  The attribute settings in the object must be valid.

       *  The stack address attribute must not be set in the object.

       *  Setting the stack size attribute to zero means leave the default stack size unchanged.

       The  pthread_getattr_default_np()  function  initializes  the  thread  attributes   object
       referred to by attr so that it contains the default attributes used for thread creation.


       EINVAL (pthread_setattr_default_np()) One of the attribute settings in attr is invalid, or
              the stack address attribute is set in attr.

       ENOMEM (pthread_setattr_default_np()) Insufficient memory.


       These functions are available in glibc since version 2.18.


       For an explanation of the terms used in this section, see attributes(7).

       │InterfaceAttributeValue   │
       │pthread_getattr_default_np(),  │ Thread safety │ MT-Safe │
       │pthread_setattr_default_np()   │               │         │


       These  functions  are  nonstandard GNU extensions; hence the suffix "_np" (nonportable) in
       their names.


       The program below uses pthread_getattr_default_np() to fetch the  default  thread-creation
       attributes  and then displays various settings from the returned thread attributes object.
       When running the program, we see the following output:

           $ ./a.out
           Stack size:          8388608
           Guard size:          4096
           Scheduling policy:   SCHED_OTHER
           Scheduling priority: 0
           Detach state:        JOINABLE
           Inherit scheduler:   INHERIT

   Program source

       #define _GNU_SOURCE
       #include <pthread.h>
       #include <stdio.h>
       #include <stdlib.h>
       #include <errno.h>

       #define errExitEN(en, msg) \
                               do { errno = en; perror(msg); \
                                    exit(EXIT_FAILURE); } while (0)

       static void
       display_pthread_attr(pthread_attr_t *attr)
           int s;
           size_t stacksize;
           size_t guardsize;
           int policy;
           struct sched_param schedparam;
           int detachstate;
           int inheritsched;

           s = pthread_attr_getstacksize(attr, &stacksize);
           if (s != 0)
               errExitEN(s, "pthread_attr_getstacksize");
           printf("Stack size:          %zd\n", stacksize);

           s = pthread_attr_getguardsize(attr, &guardsize);
           if (s != 0)
               errExitEN(s, "pthread_attr_getguardsize");
           printf("Guard size:          %zd\n", guardsize);

           s = pthread_attr_getschedpolicy(attr, &policy);
           if (s != 0)
               errExitEN(s, "pthread_attr_getschedpolicy");
           printf("Scheduling policy:   %s\n",
                   (policy == SCHED_FIFO) ? "SCHED_FIFO" :
                   (policy == SCHED_RR) ? "SCHED_RR" :
                   (policy == SCHED_OTHER) ? "SCHED_OTHER" : "[unknown]");

           s = pthread_attr_getschedparam(attr, &schedparam);
           if (s != 0)
               errExitEN(s, "pthread_attr_getschedparam");
           printf("Scheduling priority: %d\n", schedparam.sched_priority);

           s = pthread_attr_getdetachstate(attr, &detachstate);
           if (s != 0)
               errExitEN(s, "pthread_attr_getdetachstate");
           printf("Detach state:        %s\n",
                   (detachstate == PTHREAD_CREATE_DETACHED) ? "DETACHED" :
                   (detachstate == PTHREAD_CREATE_JOINABLE) ? "JOINABLE" :

           s = pthread_attr_getinheritsched(attr, &inheritsched);
           if (s != 0)
               errExitEN(s, "pthread_attr_getinheritsched");
           printf("Inherit scheduler:   %s\n",
                   (inheritsched == PTHREAD_INHERIT_SCHED) ? "INHERIT" :
                   (inheritsched == PTHREAD_EXPLICIT_SCHED) ? "EXPLICIT" :

       main(int argc, char *argv[])
           int s;
           pthread_attr_t attr;

           s = pthread_getattr_default_np(&attr);
           if (s != 0)
               errExitEN(s, "pthread_getattr_default_np");




       pthread_attr_getaffinity_np(3), pthread_attr_getdetachstate(3),
       pthread_attr_getguardsize(3), pthread_attr_getinheritsched(3),
       pthread_attr_getschedparam(3), pthread_attr_getschedpolicy(3), pthread_attr_getscope(3),
       pthread_attr_getstack(3), pthread_attr_getstackaddr(3), pthread_attr_getstacksize(3),
       pthread_attr_init(3), pthread_create(3), pthreads(7)


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