Make defined(_MSC_VER) checks consistent for -Wundef

Summary: Note: also making the `__GNUC__ || __clang__` nearby part in Pretty.h the same so that the header doesn't appear inconsistent, likewise for Hardware.h

Reviewed By: yfeldblum

Differential Revision: D19237732

fbshipit-source-id: bf3270ddf2102ea722be1eb1a557234d264f9af7

folly/CPortability.h

@@ -183,7 +183,7 @@
 #endif
 
 // attribute hidden
-#if _MSC_VER
+#if defined(_MSC_VER)
 #define FOLLY_ATTR_VISIBILITY_HIDDEN
 #elif defined(__GNUC__)
 #define FOLLY_ATTR_VISIBILITY_HIDDEN __attribute__((__visibility__("hidden")))

folly/Function.h

@@ -306,7 +306,7 @@ template <
         !std::is_reference<To>::value || std::is_reference<From>::value>::type>
 using SafeResultOf = decltype(static_cast<To>(std::declval<From>()));
 
-#if _MSC_VER
+#if defined(_MSC_VER)
 //  Need a workaround for MSVC to avoid the inscrutable error:
 //
 //      folly\function.h(...) : fatal error C1001: An internal error has

folly/chrono/Hardware.h

@@ -21,7 +21,7 @@
 #include <chrono>
 #include <cstdint>
 
-#if _MSC_VER
+#if defined(_MSC_VER)
 extern "C" std::uint64_t __rdtsc();
 #pragma intrinsic(__rdtsc)
 #endif
@@ -29,9 +29,9 @@ extern "C" std::uint64_t __rdtsc();
 namespace folly {
 
 inline std::uint64_t hardware_timestamp() {
-#if _MSC_VER
+#if defined(_MSC_VER)
   return __rdtsc();
-#elif __GNUC__ && (__i386__ || FOLLY_X64)
+#elif defined(__GNUC__) && (defined(__i386__) || FOLLY_X64)
   return __builtin_ia32_rdtsc();
 #else
   // use steady_clock::now() as an approximation for the timestamp counter on

folly/lang/Pretty.h

@@ -83,14 +83,14 @@ using pretty_default_tag = std::conditional_t< //
 
 template <typename T>
 static constexpr auto pretty_raw(pretty_tag_msc) {
-#if _MSC_VER
+#if defined(_MSC_VER)
   return pretty_carray_from(__FUNCSIG__);
 #endif
 }
 
 template <typename T>
 static constexpr auto pretty_raw(pretty_tag_gcc) {
-#if __GNUC__ || __clang__
+#if defined(__GNUC__) || defined(__clang__)
   return pretty_carray_from(__PRETTY_FUNCTION__);
 #endif
 }

folly/synchronization/AtomicUtil-inl.h

@@ -126,7 +126,7 @@ constexpr auto is_atomic<std::atomic<Integer>> = true;
 
 #if FOLLY_X64
 
-#if _MSC_VER
+#if defined(_MSC_VER)
 
 template <typename Integer>
 inline bool atomic_fetch_set_x86(