In C, it is undefined to shift an N-bit value by N.  This fixes the
problem in find_batch() for the case where i == 0.

Found by Coverity.

Reported-at: 
https://scan3.coverity.com/reports.htm#v16889/p10449/fileInstanceId=14763098&defectInstanceId=4304031&mergedDefectId=68209
Signed-off-by: Ben Pfaff <b...@ovn.org>
---
 tests/test-cmap.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tests/test-cmap.c b/tests/test-cmap.c
index e159a164f315..2c6fa89eb775 100644
--- a/tests/test-cmap.c
+++ b/tests/test-cmap.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009, 2010, 2013, 2014, 2016 Nicira, Inc.
+ * Copyright (c) 2008, 2009, 2010, 2013, 2014, 2016, 2017 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -412,7 +412,6 @@ find_batch(const struct cmap *cmap, const int value)
 {
     size_t i, ret;
     const size_t end = MIN(n_batch, n_elems - value);
-    unsigned long map = ~0;
     uint32_t hashes[N_BATCH_MAX];
     const struct cmap_node *nodes[N_BATCH_MAX];
 
@@ -431,7 +430,7 @@ find_batch(const struct cmap *cmap, const int value)
 
     ret = i;
 
-    map >>= BITMAP_ULONG_BITS - i; /* Clear excess bits. */
+    unsigned long map = i ? ~0UL >> (BITMAP_ULONG_BITS - i) : 0;
     map = cmap_find_batch(cmap, map, hashes, nodes);
 
     ULLONG_FOR_EACH_1(i, map) {
-- 
2.10.2

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