Fix Folly issues with -Wcovered-switch-default compiler flag

Summary:
When compiled with `-Wcovered-switch-default`, Folly fails to build because it adds `default` to switches which are already exhaustive. For C++ safety, these switches are intentionally including a default, so wrap them in a pragma block to indicate that and locally disable the warning.

Causes -fmodules import issues for upstream library in D30379442.

Still remaining issues with C++ definition: P445339268

Reviewed By: ispeters

Differential Revision: D30397871

fbshipit-source-id: adead9e01d0ba3b21c2e1446150cc6fed0f58602

folly/Conv.h

@@ -117,6 +117,7 @@
 #include <folly/Expected.h>
 #include <folly/FBString.h>
 #include <folly/Likely.h>
+#include <folly/Portability.h>
 #include <folly/Range.h>
 #include <folly/Traits.h>
 #include <folly/Unit.h>
@@ -641,6 +642,8 @@ toAppend(
       1); // max trailing padding zeros
   char buffer[256];
   StringBuilder builder(buffer, sizeof(buffer));
+  FOLLY_PUSH_WARNING
+  FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
   switch (mode) {
     case DoubleToStringConverter::SHORTEST:
       conv.ToShortest(value, &builder);
@@ -657,6 +660,7 @@ toAppend(
       conv.ToPrecision(value, int(numDigits), &builder);
       break;
   }
+  FOLLY_POP_WARNING
   const size_t length = size_t(builder.position());
   builder.Finalize();
   result->append(buffer, length);

folly/FBString.h

@@ -368,6 +368,8 @@ class fbstring_core {
 
   FOLLY_NOINLINE
   void reserve(size_t minCapacity, bool disableSSO = FBSTRING_DISABLE_SSO) {
+    FOLLY_PUSH_WARNING
+    FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
     switch (category()) {
       case Category::isSmall:
         reserveSmall(minCapacity, disableSSO);
@@ -381,6 +383,7 @@ class fbstring_core {
       default:
         folly::assume_unreachable();
     }
+    FOLLY_POP_WARNING
     assert(capacity() >= minCapacity);
   }
 
@@ -408,6 +411,8 @@ class fbstring_core {
   }
 
   size_t capacity() const {
+    FOLLY_PUSH_WARNING
+    FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
     switch (category()) {
       case Category::isSmall:
         return maxSmallSize;
@@ -423,6 +428,7 @@ class fbstring_core {
       default:
         break;
     }
+    FOLLY_POP_WARNING
     return ml_.capacity();
   }
 

folly/Format-inl.h

@@ -28,6 +28,7 @@
 #include <folly/Exception.h>
 #include <folly/FormatTraits.h>
 #include <folly/MapUtil.h>
+#include <folly/Portability.h>
 #include <folly/Traits.h>
 #include <folly/lang/Exception.h>
 #include <folly/lang/ToAscii.h>
@@ -313,6 +314,8 @@ void formatString(StringPiece val, FormatArg& arg, FormatCallback& cb) {
     int padChars = static_cast<int>(arg.width - val.size());
     memset(padBuf, fill, size_t(std::min(padBufSize, padChars)));
 
+    FOLLY_PUSH_WARNING
+    FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
     switch (arg.align) {
       case FormatArg::Align::DEFAULT:
       case FormatArg::Align::LEFT:
@@ -331,6 +334,7 @@ void formatString(StringPiece val, FormatArg& arg, FormatCallback& cb) {
         abort();
         break;
     }
+    FOLLY_POP_WARNING
   }
 
   cb(val);
@@ -439,6 +443,8 @@ class FormatValue<
         sign = '-';
       } else {
         uval = static_cast<UT>(val_);
+        FOLLY_PUSH_WARNING
+        FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
         switch (arg.sign) {
           case FormatArg::Sign::PLUS_OR_MINUS:
             sign = '+';
@@ -453,6 +459,7 @@ class FormatValue<
             sign = '\0';
             break;
         }
+        FOLLY_POP_WARNING
       }
     } else {
       uval = static_cast<UT>(val_);

folly/dynamic-inl.h

@@ -22,6 +22,7 @@
 #include <folly/Conv.h>
 #include <folly/Format.h>
 #include <folly/Likely.h>
+#include <folly/Portability.h>
 #include <folly/detail/Iterators.h>
 #include <folly/lang/Exception.h>
 
@@ -87,11 +88,13 @@ struct hash<::folly::dynamic> {
 } // namespace std
 
 //////////////////////////////////////////////////////////////////////
-
+/* clang-format off */
 // This is a higher-order preprocessor macro to aid going from runtime
 // types to the compile time type system.
+
 #define FB_DYNAMIC_APPLY(type, apply)                                             \
   do {                                                                            \
+    FOLLY_PUSH_WARNING FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")    \
     switch ((type)) {                                                             \
       case NULLT:                                                                 \
         apply(std::nullptr_t);                                                    \
@@ -117,8 +120,9 @@ struct hash<::folly::dynamic> {
       default:                                                                    \
         abort();                                                                  \
     }                                                                             \
+    FOLLY_POP_WARNING                                                             \
   } while (0)
-
+/* clang-format on */
 //////////////////////////////////////////////////////////////////////
 
 namespace folly {
@@ -998,6 +1002,8 @@ FOLLY_DYNAMIC_DEC_TYPEINFO(dynamic::ObjectImpl, dynamic::OBJECT)
 
 template <class T>
 T dynamic::asImpl() const {
+  FOLLY_PUSH_WARNING
+  FOLLY_CLANG_DISABLE_WARNING("-Wcovered-switch-default")
   switch (type()) {
     case INT64:
       return to<T>(*get_nothrow<int64_t>());
@@ -1013,6 +1019,7 @@ T dynamic::asImpl() const {
     default:
       throw_exception<TypeError>("int/double/bool/string", type());
   }
+  FOLLY_POP_WARNING
 }
 
 // Return a T* to our type, or null if we're not that type.