Loading message with Pthreads

Question

I want to print a nice loading message with these three fading dots, while the main thread does some heavy IO stuff. This is why I implemented this:

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
#include <stdbool.h>
static bool loadingStop;
static pthread_mutex_t loadingMutex;
void *loadingDots(void *message);
int main() {
 loadingStop = false;
 // MUTEX
 pthread_mutex_init(&loadingMutex, NULL);
 // ATTRIBUTE
 pthread_attr_t attr;
 pthread_attr_init(&attr);
 pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
 // THREAD
 pthread_t loadingThread;
 pthread_create(&loadingThread, &attr, loadingDots, (void *)"Loading (main, does something long)");
 pthread_attr_destroy(&attr);
 // SOMETHING TIME CONSUMING 
 usleep(8000000);
 // PLEASE 'LoadingDots' TO STOP
 pthread_mutex_lock(&loadingMutex);
 loadingStop = true;
 pthread_mutex_unlock(&loadingMutex);
 // WAIT FOR IT TO FINISH
 pthread_join(loadingThread, NULL);
 pthread_mutex_destroy(&loadingMutex);
 printf("This is printed after 'LoadingDots' savely quit.\n");
 return 0;
}
void *loadingDots(void *message)
{
 int c = 0;
 while (1) {
 switch (c) {
 case 0:
 printf("\r%s \r%s", (char *)message, (char*)message);
 break;
 default:
 putchar('.');
 break;
 }
 fflush(stdout);
 usleep(1000000);
 c = (c+1) % 4;
 pthread_mutex_lock(&loadingMutex);
 if (loadingStop) { break; };
 pthread_mutex_unlock(&loadingMutex);
 }
 putchar('\n');
 pthread_exit(NULL);
}

Answer 1

Mostly minor stuff

1. Good use of fflush(stdout); to insure output. Something often missed.

2. Minor: int main() { is not explicitly allowed per the standard. Better to use int main(void) {

3. Minor: Naked physical quantity. Values like height, weight, time, should have units made clear feet vs meter 327ドル.6 million mistake

   // usleep(8000000);
   #define SOME_us_TIME_CONSUMPTION (8000000 /* us */)
   usleep(SOME_us_TIME_CONSUMPTION);
   

4. Minor: Avoid printf() when fputs() will do. Avoid % issue.. BTW did you mean "safely" vs "savely"?

   // printf("This is printed after 'LoadingDots' savely quit.\n");
   fputs("This is printed after 'LoadingDots' savely quit.\n", stdout);
   // or 
   puts("This is printed after 'LoadingDots' savely quit.");
   

5. Long lines: Respect the width for the target audience - in this case code review.

   // pthread_create(&loadingThread, &attr, loadingDots, (void *)"Loading (main, does something long)");
   

6. vs.

   pthread_create(&loadingThread, &attr, loadingDots, 
    (void *)"Loading (main, does something long)");
   

7. Consider auto format. The space between bool loadingStop will likely shrink with auto formatting. Insure code is presentable even after auto formatting.

   // looks OK
   static bool loadingStop;
   static pthread_mutex_t loadingMutex;
   

8. Minor: Not a fan of {} one liners

   // if (loadingStop) { break; };
   if (loadingStop) { 
    break;
   };