'__atomic_load_8' error on 32 bit machine

[vigneswaran]

Hello,

While trying to compile the 'how-to-receive-a-million-packets' code, I got the following error.

$ ./build.sh 
/tmp/udpreceiver1-4ee1c6.o: In function `main':
udpreceiver1.c:143: undefined reference to `__atomic_load_8'
udpreceiver1.c:144: undefined reference to `__atomic_load_8'
/tmp/udpreceiver1-4ee1c6.o: In function `thread_loop':
udpreceiver1.c:67: undefined reference to `__atomic_fetch_add_8'
udpreceiver1.c:68: undefined reference to `__atomic_fetch_add_8'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

A quick google search revealed that the possible cause is incompatibility with 32 bit OS. So, I did the following changes and it worked fine (however, I am not very sure about any side effects).

--- a/udpreceiver1.c    2015-09-21 12:35:54.002816478 +0530
+++ b/udpreceiver1.c    2015-09-21 17:04:36.236634027 +0530
@@ -18,12 +18,12 @@

 struct state {
    int fd;
-   volatile uint64_t bps;
-   volatile uint64_t pps;
+   volatile uint32_t bps;
+   volatile uint32_t pps;
    struct mmsghdr messages[MAX_MSG];
    char buffers[MAX_MSG][MTU_SIZE];
    struct iovec iovecs[MAX_MSG];
-} __attribute__ ((aligned (64)));
+} __attribute__ ((aligned (32)));

 struct state *state_init(struct state *s) {
    int i;
@@ -121,8 +121,8 @@
        thread_spawn(thread_loop, state);
    }

-   uint64_t last_pps = 0;
-   uint64_t last_bps = 0;
+   uint32_t last_pps = 0;
+   uint32_t last_bps = 0;

    while (1) {
        struct timeval timeout =
@@ -137,7 +137,7 @@
            }
        }

-       uint64_t now_pps = 0, now_bps = 0;
+       uint32_t now_pps = 0, now_bps = 0;
        for (t = 0; t < thread_num; t++) {
            struct state *state = &array_of_states[t];
            now_pps += __atomic_load_n(&state->pps, 0);