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Re: CYGWIN 1.5.9-1 - Is vprintf() not thread safe?
- From: "John William" <jw2357 at hotmail dot com>
- To: cygwin at cygwin dot com
- Date: Sun, 23 May 2004 04:41:56 +0000
- Subject: Re: CYGWIN 1.5.9-1 - Is vprintf() not thread safe?
- Bcc:
<snip>
How about posting a simple test case. If you do so, I'll try and take a
look.
--
Brian Ford
Senior Realtime Software Engineer
VITAL - Visual Simulation Systems
FlightSafety International
the best safety device in any aircraft is a well-trained pilot...
#include <stdarg.h>
#include <pthread.h>
pthread_mutex_t printf_mutex;
void *thread_exec();
void myprintf(char *,...);
main()
{
pthread_t id1,id2;
char *s1="11111";
char *s2="22222";
pthread_mutex_init(&printf_mutex,NULL);
pthread_create(&id1,0,thread_exec,(void *)s1);
pthread_create(&id2,0,thread_exec,(void *)s2);
pthread_join(id1,NULL);
pthread_join(id2,NULL);}
void *thread_exec(string)
char *string;
{
int i;
for (i=0;i<10;i++)
myprintf("%s (%d)\n",string,i);
pthread_exit(NULL);
}
void myprintf(char *msg,...)
{
va_list arg;
/* pthread_mutex_lock(&printf_mutex);*/
va_start(arg, msg);
vprintf(msg, arg);
va_end(arg);
/* pthread_mutex_unlock(&printf_mutex);*/
}
When run, I get:
$ gcc t.c ; ./a.exe
11111 (0)
11111 (1)
11111 (2)
11111 (3)
11111 (4)
11111 (5)
11111 (6)11111 (6)
22222 (6)22
22222 (2)
( 22222 (3)
122222 (4))
22222 (5)11111 (8)
22222 (6)11111 (9)
22222 (7)
22222 (8)
22222 (9)
With the mutexes uncommented, I get:
$ gcc t.c ; ./a.exe
22222 (0)
22222 (1)
22222 (2)
22222 (3)
22222 (4)
22222 (5)
11111 (0)
22222 (6)
11111 (1)
22222 (7)
11111 (2)
22222 (8)
11111 (3)
22222 (9)
11111 (4)
11111 (5)
11111 (6)
11111 (7)
11111 (8)
11111 (9)
which is as expected.
For this simple test case, I was not able to get vprintf() to crash, but it
does on my more complicated application (lots of parameters passed to
vprintf()). I'm pretty sure it's not a bug in my application as putting in
the mutex locking around the vprintf() stops the crashes.
Thanks again for your help.
- John
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