libavformat/rtpproto.c:371: error: Uninitialized Value
  The value read from len was never initialized.

libavformat/rtpproto.c:371:5: 
369.             return AVERROR(EAGAIN);
370.     }
371.     return len;
         ^
372. }
373. 

static int rtp_read(URLContext *h, uint8_t *buf, int size)
{
    RTPContext *s = h->priv_data;
    struct sockaddr_storage from;
    socklen_t from_len;
    int len, n, i;
    struct pollfd p[2] = {{s->rtp_fd, POLLIN, 0}, {s->rtcp_fd, POLLIN, 0}};
    int poll_delay = h->flags & AVIO_FLAG_NONBLOCK ? 0 : 100;
    for(;;) {
        if (ff_check_interrupt(&h->interrupt_callback))
            return AVERROR_EXIT;
        n = poll(p, 2, poll_delay);
        if (n > 0) {
            for (i = 1; i >= 0; i--) {
                if (!(p[i].revents & POLLIN))
                    continue;
                from_len = sizeof(from);
                len = recvfrom(p[i].fd, buf, size, 0,
                                (struct sockaddr *)&from, &from_len);
                if (len < 0) {
                    if (ff_neterrno() == AVERROR(EAGAIN) ||
                        ff_neterrno() == AVERROR(EINTR))
                        continue;
                    return AVERROR(EIO);
                }
                if (rtp_check_source_lists(s, &from))
                    continue;
                return len;
            }
        } else if (n < 0) {
            if (ff_neterrno() == AVERROR(EINTR))
                continue;
            return AVERROR(EIO);
        }
        if (h->flags & AVIO_FLAG_NONBLOCK)
            return AVERROR(EAGAIN);
    }
    return len;
}
['static int rtp_read(URLContext *h, uint8_t *buf, int size)\n{\n    RTPContext *s = h->priv_data;\n    struct sockaddr_storage from;\n    socklen_t from_len;\n    int len, n, i;\n    struct pollfd p[2] = {{s->rtp_fd, POLLIN, 0}, {s->rtcp_fd, POLLIN, 0}};\n    int poll_delay = h->flags & AVIO_FLAG_NONBLOCK ? 0 : 100;\n    for(;;) {\n        if (ff_check_interrupt(&h->interrupt_callback))\n            return AVERROR_EXIT;\n        n = poll(p, 2, poll_delay);\n        if (n > 0) {\n            for (i = 1; i >= 0; i--) {\n                if (!(p[i].revents & POLLIN))\n                    continue;\n                from_len = sizeof(from);\n                len = recvfrom(p[i].fd, buf, size, 0,\n                                (struct sockaddr *)&from, &from_len);\n                if (len < 0) {\n                    if (ff_neterrno() == AVERROR(EAGAIN) ||\n                        ff_neterrno() == AVERROR(EINTR))\n                        continue;\n                    return AVERROR(EIO);\n                }\n                if (rtp_check_source_lists(s, &from))\n                    continue;\n                return len;\n            }\n        } else if (n < 0) {\n            if (ff_neterrno() == AVERROR(EINTR))\n                continue;\n            return AVERROR(EIO);\n        }\n        if (h->flags & AVIO_FLAG_NONBLOCK)\n            return AVERROR(EAGAIN);\n    }\n    return len;\n}']