Program to create N boring threads that do nothing, for measuring minimal per-thread memory use

threads-memory.c

#include <pthread.h>
#include <stdatomic.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#define NUM_THREADS 500
#define BYTES_PER_THREAD 1024 * 1024  // 1 MB

void *child_main(void *num_threads_ready) {
    /*
    char *data = malloc(BYTES_PER_THREAD);
    if (data == NULL) {
        fputs("failed to allocate memory", stderr);
        exit(1);
    }

    for (int i = 0; i < BYTES_PER_THREAD; i++) {
        data[i] = 0;
    }
    */
    atomic_fetch_add((atomic_uint *)num_threads_ready, 1);
    pause();
    return 0;
}

int main() {
    atomic_uint num_threads_ready;
    atomic_init(&num_threads_ready, 0);
    pthread_t threads[NUM_THREADS];
    fputs("starting threads... ", stderr);
    for (int i = 0; i < NUM_THREADS; i++) {
        if (pthread_create(&threads[i], NULL, child_main, &num_threads_ready)) {
            fputs("failed to create thread\n", stderr);
            exit(1);
        }
    }
    while (atomic_load(&num_threads_ready) < NUM_THREADS) {
        sleep(1);
    }
    fputs("done\npress enter to exit", stderr);
    getchar();
    return 0;
}