folly/AtomicHashMap-inl.h: avoid -Wsign-compare warning/error (easy)

Summary:
* folly/AtomicHashMap-inl.h (insertInternal): Do not declare
nextMapIdx to be signed ("int"), since we compare it against
variables of unsigned type.  Otherwise, gcc-4.9 would give this
diagnostic:
folly/AtomicHashMap-inl.h:99:18: error: comparison between signed and unsigned integer expressions [-Werror=sign-compare]
complaining about this comparison:
if (nextMapIdx >= kNumSubMaps_ ||

Test Plan:
Run this and note there are fewer errors than before:
fbconfig --platform-all=gcc-4.9-glibc-2.20 -r folly && fbmake dbgo

Reviewed By: philipp@fb.com

Subscribers: folly-diffs@

FB internal diff: D1770683

Tasks: 5941250

Signature: t1:1770683:1420683505:4452c7cb4f14f098be089601be906884036348ed

diff --git a/folly/AtomicHashMap-inl.h b/folly/AtomicHashMap-inl.h
index c4a0f56b8e1d0d1940ea9ace1cd67cb06656c5e9..ad4c33f394ca49eee319514053bda73d205d2dcc 100644 (file)
--- a/folly/AtomicHashMap-inl.h
+++ b/folly/AtomicHashMap-inl.h
@@ -78,7 +78,7 @@ typename AtomicHashMap<KeyT, ValueT, HashFcn, EqualFcn, Allocator>::SimpleRetT
 AtomicHashMap<KeyT, ValueT, HashFcn, EqualFcn, Allocator>::
 insertInternal(key_type key, T&& value) {
  beginInsertInternal:
-  int nextMapIdx = // this maintains our state
+  auto nextMapIdx = // this maintains our state
     numMapsAllocated_.load(std::memory_order_acquire);
   typename SubMap::SimpleRetT ret;
   FOR_EACH_RANGE(i, 0, nextMapIdx) {