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Date: Sun, 28 Sep 2008 09:32:39 +0200
From: =?UTF-8?B?VsOhY2xhdiBIYWlzbWFu?= <v DOT haisman AT sh DOT cvut DOT cz>
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To: cygwin AT cygwin DOT com
Subject: Re: crash if fork(2) from another thread
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Hirokazu Yamamoto wrote, On 28.9.2008 4:16:
> # I've post mail, but it didn't show up in
> http://www.nabble.com/Cygwin-f12165.html.
> # Maybe it was not good to attach a file. So try again...
> 
> I'm not familiar with pthread & fork, but I think following code should not
> crash. Is this expected behavior?
> 
> #include <stdio.h>
> #include <stdlib.h>
> #include <pthread.h>
> #include <assert.h>
> 
> void *thread_func(void* args)
> {
>     int ret;
>     pid_t pid;
>     pthread_t thread;
> 
>     puts("thread_func");
> 
>     pid = fork();
> 
>     assert(pid != (pid_t)-1);
> 
>     if (pid != 0) /* parent process */
>     {
>         int status;
> 
>         printf("parent process (child pid = %d)\n", pid);
> 
>         waitpid(pid, &status, 0);
> 
>         puts("parent process end");
>     }
>     else /* child process */
>     {
>         puts("child process"); /* crash here */
I think this is not allowed in here. You can only do async-signal-safe stuff
in the child. IO is AFAIK not in that category. Basically, the only thing you
 can safely do in the child process is to call exec().

>     }
> 
>     return args;
> }
> 
> int main()
> {
>     int ret;
>     pthread_t thread;
> 
>     ret = pthread_create(&thread, NULL, thread_func, NULL);
>     assert(ret == 0);
> 
>     ret = pthread_join(thread, NULL);
>     assert(ret == 0);
> }
> 
> // built with "gcc main.c -o main.exe"
> 
> Thank you.

- --
VH
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