Re: Pre-main construction order in modules

On 31.03.2025 15:32, Bonita Montero wrote:

Am 31.03.2025 um 14:26 schrieb Paavo Helde:
 

An example of pre-C++11 thread-safe Meyer singleton:
>
std::map<std::string, std::string>& GetGlobalMap() {
>
     // No dynamic initialization, so this is safe:
     static std::map<std::string, std::string>* pGlobal = NULL;
>
     // No dynamic initialization, so this is safe as well:
     static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
>
     // Initialize the global static if not yet initialized.
     pthread_mutex_lock(&mutex);
     if (!pGlobal) {
         pGlobal = new std::map<std::string, std::string>();
     }
     pthread_mutex_unlock(&mutex);
     return *pGlobal;
}

 That's rather slow. Double-checked locking as implemented for
all static locals with current runtimes is much more efficient.

Sure. That's why one should not call such a function from inside a million iteration loop. But it would often be possible to call it before the loop and use the returned reference million times inside the loop.