Example of netcdf file that will signal when used with non-threadsafe hdf5

crash.c

#include <netcdf.h>
#include <assert.h>
#include <stdint.h>
#include <pthread.h>

#define FILENAME "filename.nc"

static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_barrier_t barrier;

static void *opener(void* data) {
    (void) data;
    int err;

    int ncid;
    pthread_mutex_lock(&mutex);
    err = nc_open(FILENAME, NC_NETCDF4 | NC_NOWRITE, &ncid);
    pthread_mutex_unlock(&mutex);
    assert(!err);


    int varid;
    pthread_mutex_lock(&mutex);
    err = nc_inq_varid(ncid, "data", &varid);
    pthread_mutex_unlock(&mutex);
    assert(!err);

    int xtype;
    int ndims;
    // Calling this function whilst also calling some other function gives
    // funnt errors...

    //pthread_mutex_lock(&mutex);
    pthread_barrier_wait(&barrier);
    err = nc_inq_var(ncid, varid, NULL, &xtype, &ndims, NULL, NULL);
    //pthread_mutex_unlock(&mutex);

    assert(!err);

    pthread_mutex_lock(&mutex);
    err = nc_close(ncid);
    pthread_mutex_unlock(&mutex);
    assert(!err);

    return NULL;
}

static void *creator(void *data) {
    (void) data;
    int err;

    int ncid;
    pthread_mutex_lock(&mutex);
    err = nc_create(FILENAME, NC_NETCDF4 | NC_WRITE | NC_CLOBBER, &ncid);
    assert(!err);

    int dimid[2];
    err = nc_def_dim(ncid, "x", 3, &dimid[0]);
    assert(!err);
    err = nc_def_dim(ncid, "y", 4, &dimid[1]);
    assert(!err);

    int varid;
    err = nc_def_var(ncid, "data", NC_INT, 2, dimid, &varid);
    assert(!err);

    err = nc_close(ncid);
    pthread_mutex_unlock(&mutex);
    assert(!err);

    return NULL;
}

#define N 10

int main() {
    pthread_barrier_init(&barrier, NULL, N);

    // nc_initialize(); // Not neccessary, and does not make a difference
    creator(NULL);

    pthread_t t[N];
    for (int i = 0; i < N; i++) {
        pthread_create(&t[i], NULL, opener, NULL);
    }

    for (int i = 0; i < N; i++) {
        void *data;
        pthread_join(t[i], &data);
    }
}