CERT C: Rule POS44-C

Do not use signals to terminate threads

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Description

Rule Definition

Do not use signals to terminate threads.¹

Polyspace Implementation

The rule checker checks for Use of signal to kill thread.

Examples

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Use of signal to kill thread

Issue

Use of signal to kill thread occurs when you use an uncaught signal to kill a thread. For instance, you use the POSIX^® function pthread_kill and send the signal SIGTERM to kill a thread.

Risk

Sending a signal kills the entire process instead of just the thread that you intend to kill.

For instance, the pthread_kill specifications state that if the disposition of a signal is to terminate, this action affects the entire process.

Fix

Use other mechanisms that are intended to kill specific threads.

For instance, use the POSIX function pthread_cancel to terminate a specific thread.

Example - Use of pthread_kill to Terminate Threads

#include <signal.h>
#include <pthread.h>

void* func(void *foo) {
  /* Execution of thread */
}
 
int main(void) {
  int result;
  pthread_t thread;
 
  if ((result = pthread_create(&thread, NULL, func, 0)) != 0) {
  }
  if ((result = pthread_kill(thread, SIGTERM)) != 0) { //Noncompliant
  }
 
  /* This point is not reached because the process terminates in pthread_kill() */
 
  return 0;
}

In this example, the pthread_kill function sends the signal SIGTERM to kill a thread. The signal kills the entire process instead of the thread previously created with pthread_create.

Correction — Use pthread_cancel to Terminate Threads

One possible correction is to use the pthread_cancel function. The pthread_cancel terminates a thread specified by its first argument at a specific cancellation point or immediately, depending on the thread's cancellation type.

#include <signal.h>
#include <pthread.h>

void* func(void *foo) {
  /* Execution of thread */
}
 
int main(void) {
  int result;
  pthread_t thread;
 
  if ((result = pthread_create(&thread, NULL, func, 0)) != 0) {
    /* Handle Error */
  }
  if ((result = pthread_cancel(thread)) != 0) {
    /* Handle Error */
  }
 
  /* Continue executing */
 
  return 0;
}

Check Information

Group: Rule 50. POSIX (POS)

Version History

Introduced in R2019a

¹ This software has been created by MathWorks incorporating portions of: the “SEI CERT-C Website,” © 2017 Carnegie Mellon University, the SEI CERT-C++ Web site © 2017 Carnegie Mellon University, ”SEI CERT C Coding Standard – Rules for Developing safe, Reliable and Secure systems – 2016 Edition,” © 2016 Carnegie Mellon University, and “SEI CERT C++ Coding Standard – Rules for Developing safe, Reliable and Secure systems in C++ – 2016 Edition” © 2016 Carnegie Mellon University, with special permission from its Software Engineering Institute.

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