THREAD_SAFE_LOCALE.cpp

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// checking if locale is thread safe
 
 
// determines whether each thread has its own C locale environment
// that's independent of those of all other threads or whether the
// C locale facility is process global (i.e., shared among all
// threads)
 
 
#include <locale.h>         // for LC_ALL, setlocale()
#include <string.h>         // for strcpy()
 
#include "locale_names.h"   // for test_locale_names
#include "thread.h"         // for pthread_t, pthread_create
 
 
static char
thread_locale [3][1024];
 
 
extern "C" {
 
void* thread_routine (void *arg)
{
    const char* const name = setlocale (LC_ALL, 0);
 
    if (name) {
        const unsigned long inx = (unsigned long)arg;
 
        strcpy (thread_locale [inx], name);
    }
 
    return 0;
}
 
}   // extern "C"
 
int main ()
{
    const char* locale_name = setlocale (LC_ALL, "C");
 
    // save the main thread's locale at index 0
    strcpy (thread_locale [0], locale_name);
 
    pthread_t thread [2];
 
    // create one thread and have it save its locale name at index 1
    if (pthread_create (thread + 0, 0, thread_routine, (void*)1))
        return 4;
 
    // find a named locale different from the initial one
    for (unsigned i = 0; i != nlocales; ++i) {
        // set the main thread's locale to one that's different
        // from that of the first thread
        locale_name = setlocale (LC_ALL, test_locale_names [i]);
        if (locale_name && strcmp (locale_name, thread_locale [0]))
            break;
    }
 
    // create another thread and have it save its locale name at index 2
    if (pthread_create (thread + 1, 0, thread_routine, (void*)2)) {
        return 3;
    }
 
    // join both (sub)threads
    if (pthread_join (thread [0], 0) || pthread_join (thread [1], 0))
        return 2;
 
    // return 0 (success) when the (sub)thread's locale is different
    // from the main thread's locale and 1 (failure) when they are
    // the same
    return    0 == strcmp (thread_locale [0], thread_locale [1])
           || 0 == strcmp (thread_locale [0], thread_locale [2]);
}