BUGFIX memory leak

Since pthread_once() is called only once in a process, also the destructor
in pthread_key_create() is the same for all threads. But we use dynamic
memory for threads and static memory for the main thread. Therefore, we
have to check in destructor (and we cannot use standard free()) for freeing
static memory if someone will use pthread_exit() in main().

Fixes #15

src/common.c

@@ -44,29 +44,25 @@ static pthread_key_t ly_errno_key;
 LY_ERR ly_errno_main = LY_SUCCESS;
 #endif
 
+static void
+ly_errno_free(void *ptr)
+{
+    /* in __linux__ we use static memory in the main thread,
+     * so this check is for programs terminating the main()
+     * function by pthread_exit() :)
+     */
+    if (ptr != &ly_errno_main) {
+        free(ptr);
+    }
+}
+
 static void
 ly_errno_createkey(void)
 {
     int r;
-    void (*destr) (void *);
-
-#ifdef __linux__
-    if (getpid() == syscall(SYS_gettid)) {
-        /* main thread - use global variable instead of thread-specific variable.
-         * This is mainly for valgrind, because in case of the main thread the
-         * destructor registered by pthread_key_create() is not called since
-         * the main thread is terminated rather by return or exit than by
-         * pthread_exit(). */
-        destr = NULL;
-    } else {
-#else
-        {
-#endif /* __linux__ */
-        destr = free;
-    }
 
     /* initiate */
-    while ((r = pthread_key_create(&ly_errno_key, destr)) == EAGAIN);
+    while ((r = pthread_key_create(&ly_errno_key, ly_errno_free)) == EAGAIN);
     pthread_setspecific(ly_errno_key, NULL);
 }