fix FOLLY_SAFE_CHECK under some gcc versions

Summary: For reasons unknown, some gcc versions disliked the previous code with the constexpr pointer variable, even though most supported compilers and versions accepted it.

Reviewed By: aary, luciang

Differential Revision: D27083528

fbshipit-source-id: b225a3f211a9b51b248cc079cf11e4e25ae30460

folly/lang/SafeAssert.h

@@ -27,14 +27,15 @@
 #define FOLLY_DETAIL_SAFE_CHECK_IMPL(d, p, expr, expr_s, ...)  \
   if ((!d || ::folly::kIsDebug || ::folly::kIsSanitize) &&     \
       !static_cast<bool>(expr)) {                              \
-    static constexpr auto __folly_detail_safe_assert_arg =                     \
-        ::folly::detail::safe_assert_arg{                                      \
+    static constexpr ::folly::detail::safe_assert_arg          \
+        __folly_detail_safe_assert_arg{                        \
             FOLLY_PP_STRINGIZE(expr_s),                        \
             __FILE__,                                          \
             __LINE__,                                          \
             __PRETTY_FUNCTION__,                               \
-            ::folly::detail::safe_assert_msg_types_ptr<decltype(               \
-                ::folly::detail::safe_assert_msg_types_seq_of(__VA_ARGS__))>}; \
+            ::folly::detail::safe_assert_msg_types<decltype(   \
+                ::folly::detail::safe_assert_msg_types_seq_of( \
+                    __VA_ARGS__))>::value.data};               \
     ::folly::detail::safe_assert_terminate<p>(                 \
         __folly_detail_safe_assert_arg, __VA_ARGS__);          \
   }                                                            \
@@ -112,9 +113,6 @@ template <safe_assert_msg_type... A>
 constexpr
     typename safe_assert_msg_types<safe_assert_msg_type_s<A...>>::value_type
         safe_assert_msg_types<safe_assert_msg_type_s<A...>>::value;
-template <typename S>
-static constexpr safe_assert_msg_type const* safe_assert_msg_types_ptr =
-    safe_assert_msg_types<S>::value.data;
 
 struct safe_assert_arg {
   char const* expr;