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Date: Fri, 31 Oct 2003 11:01:55 +0100
From: manuela <manuelachessa AT tiscali DOT it>
Subject: Possible bug about thread and semaphore
X-Sender: manuelachessa AT pop DOT tiscali DOT it (Unverified)
To: cygwin AT cygwin DOT com
Message-id: <6.0.0.22.2.20031031105004.02468040@pop.tiscali.it>
MIME-version: 1.0
Content-type: text/plain; charset=us-ascii; format=flowed

Hi,
I have a problem with this code with the last version of Cygwin
(I run ipc-daemon2.exe). The program crashes after scanf ( I tested it also
with fgets) if thread timer posted sem2 at least once.
The same code works properly on Linux Suse 7.2 with gcc v. 3.3.1 and Red Hat
with gcc v. 2.9.6.

Is it my fault or Cygwin's fault?

Bye
Manuela

Here follows my code:


#include <stdio.h>
#include <string.h>

#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <time.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdlib.h>

#define DIMBUFFER 20

void send_buffer(char *a);
void * sender(void * arg);
void * timer(void * arg);


sem_t sem1;
sem_t sem2;
char buffer[DIMBUFFER];

void * sender(void * arg)
{
	while(true)
	{
	
		sem_wait(&sem2);
		sem_wait(&sem1);
		send_buffer(buffer);
		buffer[0]='\0';
		sem_post(&sem1);
		
	}
}

void * timer(void * arg)
{
	while(true)
	{
		sleep(5);
		printf("Event\n");
		sem_post(&sem2);
	}
}


int main(int argc, char *argv[])
{
	char string[DIMBUFFER];
	
	buffer[0]='\0';
	int ret;
	pthread_t id;
	pthread_t id2;

	ret = sem_init(&sem1,0,1);
	if(ret<0)
	{
		printf("error");
		exit(1);
	}

	ret = sem_init(&sem2,0,0);
	if(ret<0)
	{
		printf("error");
		exit(1);
	}

	int ret1= pthread_create(&id,NULL,sender,0);
	int ret2= pthread_create(&id2,NULL,timer,0);
	
	
	while(strcmp(string,"*"))
	{
		
		printf("inserisci stringa\n");
		scanf("%s",string);
	

		sem_wait(&sem1);


		strcpy(buffer,string);
		sem_post(&sem1);
		sem_post(&sem2);
		
	}
	return 0;
}

void send_buffer(char *a)
{
	if(strlen(a))
		printf("%s\n",a);
	else
		printf("NULL\n");

}


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