zmq crash, without curve

gistfile1.txt

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server.c
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// invoked as valgrind ./server
#include <zmq.h>

void main(void) {
    void *ctx = zmq_ctx_new();
    void *socket = zmq_socket(ctx, ZMQ_XPUB);
    zmq_bind(socket, "tcp://*:9999");
    while (1) {
        char buf[256];
        zmq_recv(socket, buf, 256, 0);
    }
}
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client.c
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// run as: while ./client; do :; done
#include <zmq.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>

// Magic constant, needs to be sufficient time to get the server processing the
// subscription but then exit before it's done.  This value was narrowed down
// based on the behavior of my computer and with the server running in valgrind
#define DELAY 2800

void main(void) {
    void *ctx = zmq_ctx_new();
    void *socket = zmq_socket(ctx, ZMQ_SUB);
    char *sub = "subscription";
    zmq_connect(socket, "tcp://localhost:9999");
    zmq_setsockopt(socket, ZMQ_SUBSCRIBE, sub, strlen(sub));
    usleep(rand() % DELAY);
}