Suppress more warnings for MSVC

Summary:
Several other warnings that aren't reasonable to disable globally occur in folly headers.

- Wrap the unreachable code warnings in MSVC specific disable blocks to prevent problems for users.
- Use more careful bit twiddling instead of negating unsigned types
- Enable a simpler overload for bool->float conversion than one which attempts float->bool.
- Delete one unneeded undef.

Reviewed By: yfeldblum

Differential Revision: D4891583

fbshipit-source-id: 4d2efda1fe720abcb083bf29b578c065127cda24

folly/Conv.h

@@ -558,7 +558,8 @@ toAppend(Src value, Tgt * result) {
   if (value < 0) {
     result->push_back('-');
     result->append(
-        buffer, uint64ToBufferUnsafe(uint64_t(-uint64_t(value)), buffer));
+        buffer,
+        uint64ToBufferUnsafe(~static_cast<uint64_t>(value) + 1, buffer));
   } else {
     result->append(buffer, uint64ToBufferUnsafe(uint64_t(value), buffer));
   }
@@ -1179,13 +1180,14 @@ parseTo(StringPiece src, Tgt& out) {
 namespace detail {
 
 /**
- * Bool to integral doesn't need any special checks, and this
+ * Bool to integral/float doesn't need any special checks, and this
  * overload means we aren't trying to see if a bool is less than
  * an integer.
  */
 template <class Tgt>
 typename std::enable_if<
-    !std::is_same<Tgt, bool>::value && std::is_integral<Tgt>::value,
+    !std::is_same<Tgt, bool>::value &&
+        (std::is_integral<Tgt>::value || std::is_floating_point<Tgt>::value),
     Expected<Tgt, ConversionCode>>::type
 convertTo(const bool& value) noexcept {
   return static_cast<Tgt>(value ? 1 : 0);

folly/Expected.h

@@ -233,6 +233,11 @@ struct ExpectedStorage {
   Value&& value() && {
     return std::move(value_);
   }
+  // TODO (t17322426): remove when VS2015 support is deprecated
+  // VS2015 static analyzer incorrectly flags these as unreachable in certain
+  // circumstances. VS2017 does not have this problem on the same code.
+  FOLLY_PUSH_WARNING
+  FOLLY_MSVC_DISABLE_WARNING(4702) // unreachable code
   Error& error() & {
     return error_;
   }
@@ -242,6 +247,7 @@ struct ExpectedStorage {
   Error&& error() && {
     return std::move(error_);
   }
+  FOLLY_POP_WARNING
 };
 
 template <class Value, class Error>
@@ -527,6 +533,11 @@ struct ExpectedStorage<Value, Error, StorageType::ePODStruct> {
   Value&& value() && {
     return std::move(value_);
   }
+  // TODO (t17322426): remove when VS2015 support is deprecated
+  // VS2015 static analyzer incorrectly flags these as unreachable in certain
+  // circumstances. VS2017 does not have this problem on the same code.
+  FOLLY_PUSH_WARNING
+  FOLLY_MSVC_DISABLE_WARNING(4702) // unreachable code
   Error& error() & {
     return error_;
   }
@@ -536,6 +547,7 @@ struct ExpectedStorage<Value, Error, StorageType::ePODStruct> {
   Error&& error() && {
     return std::move(error_);
   }
+  FOLLY_POP_WARNING
 };
 
 namespace expected_detail_ExpectedHelper {

folly/Hash.h

@@ -18,6 +18,7 @@
 
 #include <cstdint>
 #include <cstring>
+#include <limits>
 #include <string>
 #include <tuple>
 #include <type_traits>
@@ -365,7 +366,7 @@ template <>
 struct hasher<bool> {
   size_t operator()(bool key) const {
     // Make sure that all the output bits depend on the input.
-    return -static_cast<size_t>(key);
+    return key ? std::numeric_limits<size_t>::max() : 0;
   }
 };
 

folly/portability/Windows.h

@@ -44,11 +44,6 @@
 #undef CAL_GREGORIAN
 #endif
 
-// Defined in winnt.h
-#ifdef DELETE
-#undef DELETE
-#endif
-
 // Defined in the GDI interface.
 #ifdef ERROR
 #undef ERROR