Always pack small_vector

Summary:
The check was overly restrictive, the conditional packing was originally used to limit it to GCC only (as it used the `__attribute__` directly), but that restriction is no longer needed as `FOLLY_PACK_*` will be defined appropriately for whatever platform we are currently on.

This just switches it to unconditionally use the `FOLLY_PACK_*` macros rather than defining it's own `FB_PACK_*` macros.

See https://github.com/facebook/folly/commit/aafd8ff9151615a8de09682d41d1c29966e4c8fe for where the `FB_PACK_*` macros could originally have been removed.

Reviewed By: yfeldblum

Differential Revision: D3373779

fbshipit-source-id: 9e41b0836f8ba12de4f37aba58c51f841be08b41

folly/small_vector.h

@@ -46,20 +46,10 @@
 #include <folly/FormatTraits.h>
 #include <folly/Malloc.h>
 #include <folly/Portability.h>
+#include <folly/SmallLocks.h>
 #include <folly/portability/Constexpr.h>
 #include <folly/portability/Malloc.h>
 
-#if defined(__GNUC__) && (FOLLY_X64 || FOLLY_PPC64)
-# include <folly/SmallLocks.h>
-# define FB_PACK_ATTR FOLLY_PACK_ATTR
-# define FB_PACK_PUSH FOLLY_PACK_PUSH
-# define FB_PACK_POP FOLLY_PACK_POP
-#else
-# define FB_PACK_ATTR
-# define FB_PACK_PUSH
-# define FB_PACK_POP
-#endif
-
 // Ignore shadowing warnings within this file, so includers can use -Wshadow.
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wshadow"
@@ -333,7 +323,7 @@ namespace detail {
 }
 
 //////////////////////////////////////////////////////////////////////
-FB_PACK_PUSH
+FOLLY_PACK_PUSH
 template<class Value,
          std::size_t RequestedMaxInline    = 1,
          class PolicyA                     = void,
@@ -1033,7 +1023,7 @@ private:
     InternalSizeType* getCapacity() {
       return &capacity_;
     }
-  } FB_PACK_ATTR;
+  } FOLLY_PACK_ATTR;
 
   struct HeapPtr {
     // Lower order bit of heap_ is used as flag to indicate whether capacity is
@@ -1045,7 +1035,7 @@ private:
       return static_cast<InternalSizeType*>(
         detail::pointerFlagClear(heap_));
     }
-  } FB_PACK_ATTR;
+  } FOLLY_PACK_ATTR;
 
 #if (FOLLY_X64 || FOLLY_PPC64)
   typedef unsigned char InlineStorageType[sizeof(value_type) * MaxInline];
@@ -1114,9 +1104,9 @@ private:
       auto vp = detail::pointerFlagClear(pdata_.heap_);
       free(vp);
     }
-  } FB_PACK_ATTR u;
-} FB_PACK_ATTR;
-FB_PACK_POP
+  } FOLLY_PACK_ATTR u;
+} FOLLY_PACK_ATTR;
+FOLLY_PACK_POP
 
 //////////////////////////////////////////////////////////////////////
 
@@ -1143,9 +1133,3 @@ struct IndexableTraits<small_vector<T, M, A, B, C>>
 }  // namespace folly
 
 #pragma GCC diagnostic pop
-
-#ifdef FB_PACK_ATTR
-# undef FB_PACK_ATTR
-# undef FB_PACK_PUSH
-# undef FB_PACK_POP
-#endif