线程终止
以下内容翻译的是：
http://man7.org/linux/man-pages/man3/pthread_create.3.html
The new thread terminates in one of the following ways:
* It calls pthread_exit(3), specifying an exit status value that is
available to another thread in the same process that calls
pthread_join(3).
* It returns from start_routine(). This is equivalent to calling
pthread_exit(3) with the value supplied in the return statement.
* It is canceled (see pthread_cancel(3)).
* Any of the threads in the process calls exit(3), or the main thread
performs a return from main(). This causes the termination of all
threads in the process.
片段。 线程中断有以下几种方式：
线程中调用thread exit函数，该函数调用需要指定一个退出状态，如果有其他线程 thread join这个线程的话，这个状态值有用。
线程函数返回。这种方式等同于thread exit，exit的状态值等同于返回值。
调用thread cancel, 请求取消了这个线程。
在程序中任何地方、任何线程中调用了exit方法退出，包括在主线程main方法返回都将 中断所有线程。
请求取消线程
可以通过pthread_cancel函数请求取消线程。pthread_cancel函数会发送一个cancel请求给被取消线程。
另一个相关函数
pthread_testcancel
void pthread_testcancel(void);
请求投递pending状态的cancel请求。如果请求队列中有cancel请求的话，该函数请求将cancel请求投递给被取消线程。如果请求队列中没有cancel请求， 调用该函数无影响。
另外，该函数将在线程中创建一个取消点（Cancellation points），这样的话，如果一个线程除了其他执行代码之外没有取消点（Cancellation points），将响应cancel请求。
被取消线程是否会响应pthread_cancel的cancel请求取决于被取消线程的两个控制属性（可撤销属性）：state、type。state表示线程的可撤销状态，type表示线程的可撤销类型。
state可以是enabled (新创建的线程默认为enabled，表示可撤销)或者disabled。
不管state设置为enabled 还是disabled，都是调用pthread_cancel向线程发起cancel请求，如果disabled，发起的cancel请求将会保留在请求队列中，直到enabled可撤销状态state。
type可以是asynchronous或者deferred (新创建的线程默认为deferred)。如果type设置为asynchronous，表示取消操作是异步的，取消操作可能在任何时候被取消，通常会立即取消，但系统并不保证会立即取消，值得注意的是系统有时候还不保证最后就一定能取消成功。如果type设置为deferred，取消操作将延迟到被取消线程下次调用一个可以作为取消点（Cancellation points）的函数的时候。
可以作为取消点（Cancellation points）的函数列表：
参考http://man7.org/linux/man-pages/man7/pthreads.7.html
Cancellation points
POSIX.1 specifies that certain functions must, and certain other
functions may, be cancellation points. If a thread is cancelable,
its cancelability type is deferred, and a cancellation request is
pending for the thread, then the thread is canceled when it calls a
function that is a cancellation point.
The following functions are required to be cancellation points by
POSIX.1-2001 and/or POSIX.1-2008:
accept()
aio_suspend()
clock_nanosleep()
close()
connect()
creat()
fcntl() F_SETLKW
fdatasync()
fsync()
getmsg()
getpmsg()
lockf() F_LOCK
mq_receive()
mq_send()
mq_timedreceive()
mq_timedsend()
msgrcv()
msgsnd()
msync()
nanosleep()
open()
openat() [Added in POSIX.1-2008]
pause()
poll()
pread()
pselect()
pthread_cond_timedwait()
pthread_cond_wait()
pthread_join()
pthread_testcancel()
putmsg()
putpmsg()
pwrite()
read()
readv()
recv()
recvfrom()
recvmsg()
select()
sem_timedwait()
sem_wait()
send()
sendmsg()
sendto()
sigpause() [POSIX.1-2001 only (moves to "may" list in POSIX.1-2008)]
sigsuspend()
sigtimedwait()
sigwait()
sigwaitinfo()
sleep()
system()
tcdrain()
usleep() [POSIX.1-2001 only (function removed in POSIX.1-2008)]
wait()
waitid()
waitpid()
write()
writev()
The following functions may be cancellation points according to
POSIX.1-2001 and/or POSIX.1-2008:
access()
asctime()
asctime_r()
catclose()
catgets()
catopen()
chmod() [Added in POSIX.1-2008]
chown() [Added in POSIX.1-2008]
closedir()
closelog()
ctermid()
ctime()
ctime_r()
dbm_close()
dbm_delete()
dbm_fetch()
dbm_nextkey()
dbm_open()
dbm_store()
dlclose()
dlopen()
dprintf() [Added in POSIX.1-2008]
endgrent()
endhostent()
endnetent()
endprotoent()
endpwent()
endservent()
endutxent()
faccessat() [Added in POSIX.1-2008]
fchmod() [Added in POSIX.1-2008]
fchmodat() [Added in POSIX.1-2008]
fchown() [Added in POSIX.1-2008]
fchownat() [Added in POSIX.1-2008]
fclose()
fcntl() (for any value of cmd argument)
fflush()
fgetc()
fgetpos()
fgets()
fgetwc()
fgetws()
fmtmsg()
fopen()
fpathconf()
fprintf()
fputc()
fputs()
fputwc()
fputws()
fread()
freopen()
fscanf()
fseek()
fseeko()
fsetpos()
fstat()
fstatat() [Added in POSIX.1-2008]
ftell()
ftello()
ftw()
futimens() [Added in POSIX.1-2008]
fwprintf()
fwrite()
fwscanf()
getaddrinfo()
getc()
getc_unlocked()
getchar()
getchar_unlocked()
getcwd()
getdate()
getdelim() [Added in POSIX.1-2008]
getgrent()
getgrgid()
getgrgid_r()
getgrnam()
getgrnam_r()
gethostbyaddr() [SUSv3 only (function removed in POSIX.1-2008)]
gethostbyname() [SUSv3 only (function removed in POSIX.1-2008)]
gethostent()
gethostid()
gethostname()
getline() [Added in POSIX.1-2008]
getlogin()
getlogin_r()
getnameinfo()
getnetbyaddr()
getnetbyname()
getnetent()
getopt() (if opterr is nonzero)
getprotobyname()
getprotobynumber()
getprotoent()
getpwent()
getpwnam()
getpwnam_r()
getpwuid()
getpwuid_r()
gets()
getservbyname()
getservbyport()
getservent()
getutxent()
getutxid()
getutxline()
getwc()
getwchar()
getwd() [SUSv3 only (function removed in POSIX.1-2008)]
glob()
iconv_close()
iconv_open()
ioctl()
link()
linkat() [Added in POSIX.1-2008]
lio_listio() [Added in POSIX.1-2008]
localtime()
localtime_r()
lockf() [Added in POSIX.1-2008]
lseek()
lstat()
mkdir() [Added in POSIX.1-2008]
mkdirat() [Added in POSIX.1-2008]
mkdtemp() [Added in POSIX.1-2008]
mkfifo() [Added in POSIX.1-2008]
mkfifoat() [Added in POSIX.1-2008]
mknod() [Added in POSIX.1-2008]
mknodat() [Added in POSIX.1-2008]
mkstemp()
mktime()
nftw()
opendir()
openlog()
pathconf()
pclose()
perror()
popen()
posix_fadvise()
posix_fallocate()
posix_madvise()
posix_openpt()
posix_spawn()
posix_spawnp()
posix_trace_clear()
posix_trace_close()
posix_trace_create()
posix_trace_create_withlog()
posix_trace_eventtypelist_getnext_id()
posix_trace_eventtypelist_rewind()
posix_trace_flush()
posix_trace_get_attr()
posix_trace_get_filter()
posix_trace_get_status()
posix_trace_getnext_event()
posix_trace_open()
posix_trace_rewind()
posix_trace_set_filter()
posix_trace_shutdown()
posix_trace_timedgetnext_event()
posix_typed_mem_open()
printf()
psiginfo() [Added in POSIX.1-2008]
psignal() [Added in POSIX.1-2008]
pthread_rwlock_rdlock()
pthread_rwlock_timedrdlock()
pthread_rwlock_timedwrlock()
pthread_rwlock_wrlock()
putc()
putc_unlocked()
putchar()
putchar_unlocked()
puts()
pututxline()
putwc()
putwchar()
readdir()
readdir_r()
readlink() [Added in POSIX.1-2008]
readlinkat() [Added in POSIX.1-2008]
remove()
rename()
renameat() [Added in POSIX.1-2008]
rewind()
rewinddir()
scandir() [Added in POSIX.1-2008]
scanf()
seekdir()
semop()
setgrent()
sethostent()
setnetent()
setprotoent()
setpwent()
setservent()
setutxent()
sigpause() [Added in POSIX.1-2008]
stat()
strerror()
strerror_r()
strftime()
symlink()
symlinkat() [Added in POSIX.1-2008]
sync()
syslog()
tmpfile()
tmpnam()
ttyname()
ttyname_r()
tzset()
ungetc()
ungetwc()
unlink()
unlinkat() [Added in POSIX.1-2008]
utime() [Added in POSIX.1-2008]
utimensat() [Added in POSIX.1-2008]
utimes() [Added in POSIX.1-2008]
vdprintf() [Added in POSIX.1-2008]
vfprintf()
vfwprintf()
vprintf()
vwprintf()
wcsftime()
wordexp()
wprintf()
wscanf()
An implementation may also mark other functions not specified in the
standard as cancellation points. In particular, an implementation is
likely to mark any nonstandard function that may block as a cancella‐
tion point. (This includes most functions that can touch files.)
这两个属性可分别通过pthread_setcancelstate和pthread_setcanceltype函数设置。
int oldstate;
pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
printf("pre cancel state %d\n", oldstate);
如果设置为PTHREAD_CANCEL_ENABLE，表示enabled，如果设置为PTHREAD_CANCEL_DISABLE，表示disabled。
int oldtype;
pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype);
printf("pre cancel type %d\n", oldtype);
如果设置为PTHREAD_CANCEL_DEFERRED，表示deferred ，如果设置为PTHREAD_CANCEL_ASYNCHRONOUS，表示asynchronous。
线程的这两个控制属性（可撤销属性）：state、type默认分别为：PTHREAD_CANCEL_ENABLE、PTHREAD_CANCEL_DEFERRED。
第一种情况：通过pthread_exit函数终止线程执行。
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
int *exitStatus = NULL;
int count = 0;
void* run_up(void *arg)
{
printf("&exitStatus: %d, exitStatus: %d, *exitStatus: %d, &*exitStatus: %d\n", &exitStatus, exitStatus, *exitStatus, &*exitStatus);
pthread_exit((void *) exitStatus);
//pthread_exit(NULL);
//const char *s = "Thread funtion finished!";
//pthread_exit((void *) s);
//return (void *) exitStatus;
//return NULL;
//return (void *) "Thread funtion finished!";
}
int main()
{
exitStatus = (int *) malloc(sizeof(int));
*exitStatus = 8;
pthread_t pthread1, pthread2;
pthread_create(&pthread1,
NULL,
run_up,
(void *) 0);
int *p_status = (int *) malloc(sizeof(int));
int **status = &p_status;
pthread_join(pthread1, (void **) status);
printf("&p_status: %d, p_status: %d, *p_status: %d, &*p_status: %d\n", &p_status, p_status, *p_status, &*p_status);
printf("&status: %d, status: %d, *status: %d, &*status: %d, **status: %d, &**status: %d\n", &status, status, *status, &*status, **status, &**status);
printf("final count: %d\n", count);
return 0;
}
include_pthread = /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/include lib_pthread = /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib OUTPUT = ../Debug/ objs = $(OUTPUT)*.o make: make-std make-nostd: clean g++ -c pthread_exit_test2.cpp -o ../Debug/pthread_exit_test2.o # -L$(lib_pthread) 指定lib库文件的位置：-L/cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib # 如果没有指定lib库文件的位置：-L$(lib_pthread)，需要将lib库文件拷贝到可以查找到的目录下。我这里是cygwin # 环境: $ cp -rf /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib/libpthreadGC2.a /cygdrive/d/sbin/lib # 这样就可以不指定lib库文件的位置： # g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -lpthreadGC2 g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -L$(lib_pthread) -lpthreadGC2 # g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -lpthreadGC2 make-std: clean g++ -c pthread_exit_test2.cpp -o ../Debug/pthread_exit_test2.o g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -lpthread clean: rm -Rf ./*.bak rm -Rf ./*.o rm -Rf ./*.exe rm -Rf ../Debug/*
pthread使用的是win版本：pthreads-w32-2-8-0-release，Pre-built中包含支持linux的pthread库：libpthreadGC2.a、libpthreadGCE2.a
将Pre-built中包含支持linux的pthread库拷贝到cygwin下：/cygdrive/d/sbin/lib
$ cp -rf /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib/libpthreadGC2.a /cygdrive/d/sbin/lib/
make
$ make -f pthread_exit_test2.Makefile make
运行
$ ./pthread_exit_test2.exe
运行结果
&exitStatus: 4210712, exitStatus: 536937064, *exitStatus: 8, &*exitStatus: 536937064 &p_status: 2272376, p_status: 536937064, *p_status: 8, &*p_status: 536937064 &status: 2272372, status: 2272376, *status: 536937064, &*status: 2272376, **status: 8, &**status: 536937064
这个结果是正常的。
第二种情况：线程函数返回。
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
int *exitStatus = NULL;
void* run_up(void *arg)
{
printf("&exitStatus: %d, exitStatus: %d, *exitStatus: %d, &*exitStatus: %d\n", &exitStatus, exitStatus, *exitStatus, &*exitStatus);
return (void *) exitStatus;
//return NULL;
//return (void *) "Thread funtion finished!";
}
int main()
{
exitStatus = (int *) malloc(sizeof(int));
*exitStatus = 8;
pthread_t pthread1, pthread2;
pthread_create(&pthread1,
NULL,
run_up,
(void *) 0);
int *p_status = (int *) malloc(sizeof(int));
int **status = &p_status;
pthread_join(pthread1, (void **) status);
printf("&p_status: %d, p_status: %d, *p_status: %d, &*p_status: %d\n", &p_status, p_status, *p_status, &*p_status);
printf("&status: %d, status: %d, *status: %d, &*status: %d, **status: %d, &**status: %d\n", &status, status, *status, &*status, **status, &**status);
return 0;
}
第三种情况：通过pthread_cancel函数取消线程执行。
线程的可撤销type属性为deferred的例子：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <sys/types.h>
int *exitStatus = NULL;
void* run_up(void *arg)
{
pid_t pid = getpid();
// pid_t tid = gettid(); // Glibc does not provide a wrapper for this system call; call it using syscall(2).
pthread_t tid = pthread_self();
int i = 0;
//int oldstate;
//int oldtype;
printf("pid: %ld, tid: %ld\n", pid, tid);
printf("&exitStatus: %d, exitStatus: %d, *exitStatus: %d, &*exitStatus: %d\n", &exitStatus, exitStatus, *exitStatus, &*exitStatus);
//pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
//printf("pre cancel state %d\n", oldstate);
//pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype);
//printf("pre cancel type %d\n", oldtype);
while(1)
{
i++;
sleep(1);
pthread_testcancel();
}
return (void *) exitStatus;
}
int main()
{
exitStatus = (int *) malloc(sizeof(int));
*exitStatus = 8;
pthread_t pthread1, pthread2;
int result = pthread_create(&pthread1,
NULL,
run_up,
(void *) 0);
if (result)
{
printf("error: pthread_create, errno: %d\n", result);
}
printf("pthread: %ld\n", pthread1);
printf("try to cancel thread %ld\n", pthread1);
pthread_cancel(pthread1);
int *p_status = (int *) malloc(sizeof(int));
int **status = &p_status;
result = pthread_join(pthread1, (void **) status);
if (result)
{
printf("error: pthread_join, errno: %d\n", result);
}
if (p_status == NULL)
{
printf("p_status is null\n");
}
else if (p_status == PTHREAD_CANCELED)
{
printf("thread %ld canceled.\n", pthread1);
}
else
{
printf("&p_status: %d, p_status: %d, *p_status: %d, &*p_status: %d\n", &p_status, p_status, *p_status, &*p_status);
printf("&status: %d, status: %d, *status: %d, &*status: %d, **status: %d, &**status: %d\n", &status, status, *status, &*status, **status, &**status);
}
return 0;
}
这里要注意的是，线程执行函数run_up中while循环中的sleep(1);pthread_testcancel();函数调用，这两个都是可以作为取消点（Cancellation points）的函数。有这种函数调用，在向线程发起cancel请求后，线程在收到该请求后会延迟到这种函数调用的时候取消线程执行。
线程的可撤销type属性为asynchronous的例子：
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <sys/types.h>
int *exitStatus = NULL;
void* run_up(void *arg)
{
pid_t pid = getpid();
// pid_t tid = gettid(); // Glibc does not provide a wrapper for this system call; call it using syscall(2).
pthread_t tid = pthread_self();
int i = 0;
//int oldstate;
int oldtype;
printf("pid: %ld, tid: %ld\n", pid, tid);
printf("&exitStatus: %d, exitStatus: %d, *exitStatus: %d, &*exitStatus: %d\n", &exitStatus, exitStatus, *exitStatus, &*exitStatus);
//pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, &oldstate);
//printf("pre cancel state %d\n", oldstate);
//pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, &oldtype);
//printf("pre cancel type %d\n", oldtype);
pthread_setcanceltype(PTHREAD_CANCEL_ASYNCHRONOUS, &oldtype);
printf("pre cancel type %d\n", oldtype);
while(1)
{
i++;
}
return (void *) exitStatus;
}
int main()
{
exitStatus = (int *) malloc(sizeof(int));
*exitStatus = 8;
pthread_t pthread1, pthread2;
int result = pthread_create(&pthread1,
NULL,
run_up,
(void *) 0);
if (result)
{
printf("error: pthread_create, errno: %d\n", result);
}
printf("pthread: %ld\n", pthread1);
printf("try to cancel thread %ld\n", pthread1);
pthread_cancel(pthread1);
int *p_status = (int *) malloc(sizeof(int));
int **status = &p_status;
result = pthread_join(pthread1, (void **) status);
if (result)
{
printf("error: pthread_join, errno: %d\n", result);
}
if (p_status == NULL)
{
printf("p_status is null\n");
}
else if (p_status == PTHREAD_CANCELED)
{
printf("thread %ld canceled.\n", pthread1);
}
else
{
printf("&p_status: %d, p_status: %d, *p_status: %d, &*p_status: %d\n", &p_status, p_status, *p_status, &*p_status);
printf("&status: %d, status: %d, *status: %d, &*status: %d, **status: %d, &**status: %d\n", &status, status, *status, &*status, **status, &**status);
}
return 0;
}
这里要注意的是，线程执行函数run_up中while循环中并没有sleep(1);pthread_testcancel();这样的函数调用（可以作为取消点（Cancellation points）的函数）。通常被取消线程是可以取消执行的，但有时候最后也不能保证线程取消成功。
为了保证线程最后可以被取消成功，可以像上面的例子那样尝试调用一个可以作为取消点（Cancellation points）的函数。如像上面那样在循环里边调用sleep(1);pthread_testcancel();
或者在发起cancel请求的时候多尝试几次：
pthread_cancel(pthread1);
int tryt = 0;
while (tryt < 100)
{
pthread_cancel(pthread1);
sleep(0.1);
tryt++;
}
pthread w32版本线程终止（pthread_exit）后通过pthread_join获取线程终止返回值的问题
pthread w32版本线程终止（pthread_exit）后的返回值的问题。
通过pthread_exit终止线程的执行，pthread_join等待线程终止返回的值在pthread w32版本和标准pthread不一样。
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <pthread.h>
int *exitStatus = NULL;
int count = 0;
void* run_up(void *arg)
{
printf("&exitStatus: %d, exitStatus: %d, *exitStatus: %d, &*exitStatus: %d\n", &exitStatus, exitStatus, *exitStatus, &*exitStatus);
pthread_exit((void *) exitStatus);
//pthread_exit(NULL);
//const char *s = "Thread funtion finished!";
//pthread_exit((void *) s);
//return (void *) exitStatus;
//return NULL;
//return (void *) "Thread funtion finished!";
}
int main()
{
exitStatus = (int *) malloc(sizeof(int));
*exitStatus = 8;
pthread_t pthread1, pthread2;
pthread_create(&pthread1,
NULL,
run_up,
(void *) 0);
int *p_status = (int *) malloc(sizeof(int));
int **status = &p_status;
pthread_join(pthread1, (void **) status);
printf("&p_status: %d, p_status: %d, *p_status: %d, &*p_status: %d\n", &p_status, p_status, *p_status, &*p_status);
printf("&status: %d, status: %d, *status: %d, &*status: %d, **status: %d, &**status: %d\n", &status, status, *status, &*status, **status, &**status);
printf("final count: %d\n", count);
return 0;
}
include_pthread = /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/include lib_pthread = /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib OUTPUT = ../Debug/ objs = $(OUTPUT)*.o make: make-std make-nostd: clean g++ -c pthread_exit_test2.cpp -o ../Debug/pthread_exit_test2.o # -L$(lib_pthread) 指定lib库文件的位置：-L/cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib # 如果没有指定lib库文件的位置：-L$(lib_pthread)，需要将lib库文件拷贝到可以查找到的目录下。我这里是cygwin # 环境: $ cp -rf /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib/libpthreadGC2.a /cygdrive/d/sbin/lib # 这样就可以不指定lib库文件的位置： # g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -lpthreadGC2 g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -L$(lib_pthread) -lpthreadGC2 # g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -lpthreadGC2 make-std: clean g++ -c pthread_exit_test2.cpp -o ../Debug/pthread_exit_test2.o g++ $(objs) -o $(OUTPUT)pthread_exit_test2 -lpthread clean: rm -Rf ./*.bak rm -Rf ./*.o rm -Rf ./*.exe rm -Rf ../Debug/*
pthread使用的是win版本：pthreads-w32-2-8-0-release，Pre-built中包含支持linux的pthread库：libpthreadGC2.a、libpthreadGCE2.a
将Pre-built中包含支持linux的pthread库拷贝到cygwin下：/cygdrive/d/sbin/lib
$ cp -rf /cygdrive/d/usr/lib/pthreads-w32-2-8-0-release/Pre-built.2/lib/libpthreadGC2.a /cygdrive/d/sbin/lib/
make
$ make -f pthread_exit_test2.Makefile make
运行
$ ./pthread_exit_test2.exe
运行结果
&exitStatus: 4210712, exitStatus: 536937064, *exitStatus: 8, &*exitStatus: 536937064 &p_status: 2272376, p_status: 536937064, *p_status: 8, &*p_status: 536937064 &status: 2272372, status: 2272376, *status: 536937064, &*status: 2272376, **status: 8, &**status: 536937064
这个结果是正常的。
但奇怪的是，如果pthread使用的是win版本：pthreads-w32-2-8-0-release
make
$ make -f pthread_exit_test2.Makefile make-nostd
运行
$ ./pthread_exit_test2.exe
运行结果
运行输出：
&p_status: 2272376, p_status: 536937080, *p_status: 0, &*p_status: 536937080 &exitStatus: 4210712, exitStatus: 536937064, *exitStatus: 8, &*exitStatus: 536937064 &status: 2272372, status: 2272376, *status: 536937080, &*status: 2272376, **status: 0, &**status: 536937080
这个结果就不正常了，和预期结果不一致。
有时候还没打印出exitStatus的值：
&p_status: 2272376, p_status: 536937080, *p_status: 0, &*p_status: 536937080 &status: 2272372, status: 2272376, *status: 536937080, &*status: 2272376, **status: 0, &**status: 536937080
这个就奇怪了。
这个问题后来看了下，发现pthread_join函数调用失败，返回错误：error: errno: 3
根据errno.h中的定义：
#define ESRCH 3 /* No such process */
No thread with the ID thread could be found.
意思是没找到这个线程？
所以这里pthread_join调用后并没有获取到线程终止后的返回值，并没有将线程终止后的返回值拷贝到pthread_join的第二个参数。
只是我在线程函数中可以打印出线程id， 而且和printf("pthread: %ld\n", pthread1);打印出来的值是一致的，而且线程函数也执行了，怎么就找不到这个线程呢？
pid_t pid = getpid();
// pid_t tid = gettid(); // Glibc does not provide a wrapper for this system call; call it using syscall(2).
pthread_t tid = pthread_self();
printf("pid: %ld, tid: %ld\n", pid, tid);
那么这个pthread_join调用失败具体是什么原因？
关于线程执行返回值，线程执行终止返回有4中方式，可以通过pthread_join函数得到线程终止时的返回值，前提是对应的线程是joinable的（线程可以是joinable或者detached的）。参考文章：https://lobin.iteye.com/blog/2040285