Start compiling a bit of `-Wshadow`

Summary: Sometimes variable shadowing is fine, sometimes it can cause subtle mistakes.

Reviewed By: yfeldblum

Differential Revision: D3140450

fb-gh-sync-id: acf7195ad65614d4f012bef8ce7dccb3a3038456
fbshipit-source-id: acf7195ad65614d4f012bef8ce7dccb3a3038456

folly/Format.cpp

@@ -214,11 +214,11 @@ void FormatArg::initSlow() {
     }
 
     auto readInt = [&] {
-      auto const b = p;
+      auto const c = p;
       do {
         ++p;
       } while (p != end && *p >= '0' && *p <= '9');
-      return to<int>(StringPiece(b, p));
+      return to<int>(StringPiece(c, p));
     };
 
     if (*p == '*') {
@@ -242,12 +242,12 @@ void FormatArg::initSlow() {
     }
 
     if (*p == '.') {
-      auto b = ++p;
+      auto d = ++p;
       while (p != end && *p >= '0' && *p <= '9') {
         ++p;
       }
-      if (p != b) {
-        precision = to<int>(StringPiece(b, p));
+      if (p != d) {
+        precision = to<int>(StringPiece(d, p));
         if (p != end && *p == '.') {
           trailingDot = true;
           ++p;

folly/SocketAddress.cpp

@@ -36,7 +36,7 @@ namespace {
  * A structure to free a struct addrinfo when it goes out of scope.
  */
 struct ScopedAddrInfo {
-  explicit ScopedAddrInfo(struct addrinfo* info) : info(info) {}
+  explicit ScopedAddrInfo(struct addrinfo* addrinfo) : info(addrinfo) {}
   ~ScopedAddrInfo() {
     freeaddrinfo(info);
   }

folly/detail/RangeSse42.cpp

@@ -115,11 +115,9 @@ size_t qfind_first_byte_of_needles16(const StringPieceLite haystack,
   // Now, we can do aligned loads hereafter...
   size_t i = nextAlignedIndex(haystack.data());
   for (; i < haystack.size(); i+= 16) {
-    auto arr1 = _mm_load_si128(
-        reinterpret_cast<const __m128i*>(haystack.data() + i));
-    auto index = _mm_cmpestri(
-        arr2, needles.size(),
-        arr1, haystack.size() - i, 0);
+    arr1 =
+        _mm_load_si128(reinterpret_cast<const __m128i*>(haystack.data() + i));
+    index = _mm_cmpestri(arr2, needles.size(), arr1, haystack.size() - i, 0);
     if (index < 16) {
       return i + index;
     }
@@ -211,7 +209,7 @@ size_t qfind_first_byte_of_sse42(const StringPieceLite haystack,
 
   size_t i = nextAlignedIndex(haystack.data());
   for (; i < haystack.size(); i += 16) {
-    auto ret = scanHaystackBlock<true>(haystack, needles, i);
+    ret = scanHaystackBlock<true>(haystack, needles, i);
     if (ret != std::string::npos) {
       return ret;
     }