Programming

Hello!
First of all, sorry for my English, I'm not a native English speaker.

I know, that printf() function uses write() function. "man cancellation" says that write() function is a cancellation point. But when I call pthread_cancel() for my thread, which calls printf() in infinite cycle, it doesn't cancel! It means there are no cancellation points in printf(). But how is it possible? write() is a cancellation point, printf() uses write() and there are no cancellation points in printf()... I'm confused...

Could anybody please explain to me what the matter is?

P.S. The system is Solaris 10.

The write() call for printf is deferred - meaning it doesn't happen until the buffer printf is using becomes full or is flushed.

But what you are saying means that the thread is not cancellable. Not that printf does not call write().

See man pthread_setcancelstate()

Here's my program (lite version ):

Code:

#include <stdio.h>
#include <pthread.h>

#define STR	"Windows must die\n"
#define TIMEOUT	2

void* start(void* p) {
  int i = 0;  

  pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);	  // line_D
	
  for (i = 0;; ++i) {
    //write(1, STR, strlen(STR)); // line_A
    //pthread_testcancel();   // line_B   
    printf("%s", STR);   // line_C
  }
	
  return NULL;
}

int main() {
  int loc = 0;
  pthread_t thread;

  setvbuf(stdout, NULL, _IONBF, 0);
  pthread_create(&thread, NULL, start, NULL);
  sleep(TIMEOUT);
  pthread_cancel(thread);
  pthread_exit(0);
  return 0;
}

If I comment line_C and line_B and uncomment (I'm not sure that this word is exist, but I hope you forgive me, if I'm wrong ) line_A, it works fine (terminates in 2 seconds). And I understand why it does.
If I comment line_A and uncomment line_B and line_C, it works fine too.
But I can't understand, why it doesn't work when I comment line_A and line_B and uncomment line_C!
I added line_D after your reply, but it doesn't change anything.
Maybe, I have to specify some compilation keys? I compile the program by using "gcc prog_name.c" command.

try compiling like so :
gcc prog_name.c -lpthread

Doesn't work too. In modern versions all the lpthread and lthread functions are included into libc, and lpthread and lthread are only the filters for libc. So it isn't necessary to compile programs with -lpthread.