From f43ad85eddf708bb1c1d87cd6a1e7e60a9191dd6 Mon Sep 17 00:00:00 2001
From: Ben Noordhuis <info@bnoordhuis.nl>
Date: Thu, 25 Oct 2012 04:26:56 +0200
Subject: [PATCH] include: fix ngx_queue_foreach() macro

Guard against the possibility that the queue is emptied while we're iterating
over it. Simple test case:

  #include "ngx-queue.h"
  #include <assert.h>

  int main(void) {
    ngx_queue_t h;
    ngx_queue_t v[2];
    ngx_queue_t* q;
    unsigned n = 0;
    ngx_queue_init(&h);
    ngx_queue_insert_tail(&h, v + 0);
    ngx_queue_insert_tail(&h, v + 1);
    ngx_queue_foreach(q, &h) {
      ngx_queue_remove(v + 0);
      ngx_queue_remove(v + 1);
      n++;
    }
    assert(n == 1); // *not* 2
    return 0;
  }

Fixes #605.
---
 include/uv-private/ngx-queue.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/uv-private/ngx-queue.h b/include/uv-private/ngx-queue.h
index 6fd0071ff..08fd655a1 100644
--- a/include/uv-private/ngx-queue.h
+++ b/include/uv-private/ngx-queue.h
@@ -101,7 +101,7 @@ struct ngx_queue_s {
 
 #define ngx_queue_foreach(q, h)                                               \
     for ((q) = ngx_queue_head(h);                                             \
-         (q) != ngx_queue_sentinel(h);                                        \
+         (q) != ngx_queue_sentinel(h) && !ngx_queue_empty(h);                 \
          (q) = ngx_queue_next(q))