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The C++ Standard, [thread.mutex.class], paragraph 5 [ISO/IEC 14882-2014], states the following:
The behavior of a program is undefined if it destroys a
mutexobject owned by any thread or a thread terminates while owning amutexobject.
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This compliant solution eliminates the race condition by extending the lifetime of the mutex:.
| Code Block | ||||
|---|---|---|---|---|
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#include <mutex>
#include <thread>
const size_t maxThreads = 10;
void do_work(size_t i, std::mutex *pm) {
std::lock_guard<std::mutex> lk(*pm);
// Access data protected by the lock.
}
std::mutex m;
void start_threads() {
std::thread threads[maxThreads];
for (size_t i = 0; i < maxThreads; ++i) {
threads[i] = std::thread(do_work, i, &m);
}
}
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This compliant solution eliminates the race condition by joining the threads before the mutex's destructor is invoked:.
| Code Block | ||||
|---|---|---|---|---|
| ||||
#include <mutex>
#include <thread>
const size_t maxThreads = 10;
void do_work(size_t i, std::mutex *pm) {
std::lock_guard<std::mutex> lk(*pm);
// Access data protected by the lock.
}
void run_threads() {
std::thread threads[maxThreads];
std::mutex m;
for (size_t i = 0; i < maxThreads; ++i) {
threads[i] = std::thread(do_work, i, &m);
}
for (size_t i = 0; i < maxThreads; ++i) {
threads[i].join();
}
} |
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