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#include <threads.h>
#include <stdlib.h>
/* Global key to the thread-specific storage */
tss_t key;
enum { MAX_THREADS = 3 };
/* ... Other functions are unchanged */
void destructor(void *data) {
free(data);
}
int main(void) {
thrd_t thread_id[MAX_THREADS];
/* Create the key before creating the threads */
if (thrd_success != tss_create(&key, destructor)) {
/* Handle error */
}
/* Create threads that would store specific storage */
for (size_t i = 0; i < MAX_THREADS; i++) {
if (thrd_success != thrd_create(&thread_id[i], function, NULL)) {
/* Handle error */
}
}
for (size_t i = 0; i < MAX_THREADS; i++) {
if (thrd_success != thrd_join(thread_id[i], NULL)) {
/* Handle error */
}
}
tss_delete(key);
return 0;
} |
Defect Report #416 states that "the standard does not specify if or when destructors for thread-specific data keys (created with the tss_create function) are invoked." The key observation from WG14 committee discussion concerns the deliberate underspecification of threads to allow the greatest opportunity for implementation on a variety of operating systems. Consequently, it is important to consult the documentation for the specific implementation before adopting this or similar solutions using destructors for thread-specific data keys.
Risk Assessment
Failing to free thread-specific objects results in memory leaks and could result in a denial-of-service attack.
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