man pthread_detach
pthread_t
類型定義： typedef unsigned long int pthread_t; //come from /usr/include/bits/pthread.h
用途：pthread_t用于聲明線程ID。 sizeof (pthread_t) =4;
linux線程執(zhí)行和windows不同，pthread有兩種狀態(tài)joinable狀態(tài)和unjoinable狀態(tài)
一個(gè)線程默認(rèn)的狀態(tài)是joinable，如果線程是joinable狀態(tài)，當(dāng)線程函數(shù)自己返回退出時(shí)或pthread_exit時(shí)都不會(huì)釋放線程所占用堆棧和線程描述符（總計(jì)8K多）。只有當(dāng)你調(diào)用了pthread_join之后這些資源才會(huì)被釋放。
若是unjoinable狀態(tài)的線程，這些資源在線程函數(shù)退出時(shí)或pthread_exit時(shí)自動(dòng)會(huì)被釋放。
unjoinable屬性可以在pthread_create時(shí)指定，或在線程創(chuàng)建后在線程中pthread_detach自己, 如：pthread_detach(pthread_self())，將狀態(tài)改為unjoinable狀態(tài)，確保資源的釋放。如果線程狀態(tài)為 joinable,需要在之后適時(shí)調(diào)用pthread_join.
pthread_self()函數(shù)用來(lái)獲取當(dāng)前調(diào)用該函數(shù)的線程的線程ID
NAME
pthread_self - get the calling thread ID
SYNOPSIS
#include <pthread.h>
pthread_t pthread_self(void);
DESCRIPTION
The pthread_self() function shall return the thread ID of the calling thread.
RETURN VALUE
Refer to the DESCRIPTION.
ERRORS
No errors are defined.
The pthread_self() function shall not return an error code of [EINTR].
The following sections are informative.
/*example：test.c*/
#include<pthread.h>
#include<stdio.h>
#include<unistd.h>
void print_message( void *ptr );
int main( int argc, char *argv[] )
{
pthread_t thread_id;
while( 1 )
{
pthread_create( &thread_id, NULL, (void *)print_message, (void *)NULL );// 一個(gè)線程默認(rèn)的狀態(tài)是joinable
}
return 0;
}
void print_message( void *ptr )
{
pthread_detach(pthread_self());//pthread_detach(pthread_self())，將狀態(tài)改為unjoinable狀態(tài)，確保資源的釋放
static int g;
printf("%d\n", g++);
pthread_exit(0) ;//pthread_exit時(shí)自動(dòng)會(huì)被釋放
}