SEI CERT C++ Coding Standard

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changes.mady.by.user David Keaton

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changes.mady.by.user David Keaton

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Comment: Changed variable names to be less confusing and updated references.

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Code Block
bgColor#ffcccc
langc
#include <mutex>
#include <thread>

const size_t max_threads = 10;

void do_work(size_t i, std::mutex *lockppm)
{
  std::lock_guard<std::mutex> guard(*lockppm);

  // Access data protected by the lock.
}

void start_threads(void)
{
  std::thread threads[max_threads];
  std::mutex lockm;

  for (size_t i = 0; i < max_threads; ++i) {
    threads[i] = std::thread(do_work, i, &lockm);
  }
}

Compliant Solution

This compliant solution eliminates the race condition by extending the lifetime of the lock:

Code Block
bgColor#ccccff
langc
#include <mutex>
#include <thread>

const size_t max_threads = 10;

void do_work(size_t i, std::mutex *lockppm)
{
  std::lock_guard<std::mutex> guard(*lockppm);

  // Access data protected by the lock.
}

std::mutex lockm;

void start_threads(void)
{
  std::thread threads[max_threads];

  for (size_t i = 0; i < max_threads; ++i) {
    threads[i] = std::thread(do_work, i, &lockm);
  }
}

Compliant Solution

This compliant solution eliminates the race condition by joining the threads before the lockmutex's destructor is invoked:

Code Block
bgColor#ccccff
langc
#include <mutex>
#include <thread>

const size_t max_threads = 10;

void do_work(size_t i, std::mutex *lockppm)
{
  std::lock_guard<std::mutex> guard(*lockppm);

  // Access data protected by the lock.
}
void run_threads(void)
{
  std::thread threads[max_threads];
  std::mutex lockm;

  for (size_t i = 0; i < max_threads; ++i) {
    threads[i] = std::thread(do_work, i, &lockm);
  }

  for (size_t i = 0; i < max_threads; ++i) {
    threads[i].join();
  }
}

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Tool

Version

Checker

Description

 

 

Fortify SCA

5.0 

Can detect violations of this rule with CERT C Rule Pack

 
   Parasoft C/C++test9.5BD-RES-FREE, BD-RES-INVFREE 

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

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MITRE CWECWE-667, Improper Locking

Bibliography

[ISO/IEC 9899:201114882-2014]7.26.4.1, "The mtx_destroy Function[thread.mutex] "Mutual exclusion"

 

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