Fix compilation error with GCC on OSX (issue #490). (#491)

src/sysinfo.cc

@@ -73,22 +73,14 @@ BENCHMARK_NORETURN void PrintErrorAndDie(Args&&... args) {
 
 #ifdef BENCHMARK_HAS_SYSCTL
 
-#ifdef __GNUC__
-// Suppress the warning generated by the C11 flexible array member below.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wpedantic"
-#endif
-
 /// ValueUnion - A type used to correctly alias the byte-for-byte output of
 /// `sysctl` with the result type it's to be interpreted as.
 struct ValueUnion {
   union DataT {
     uint32_t uint32_value;
     uint64_t uint64_value;
-    // FIXME (Maybe?): This is a C11 flexible array member, and not technically
-    // C++. However, all compilers support it and it allows for correct aliasing
-    // of union members from bytes.
-    char bytes[];
+    // For correct aliasing of union members from bytes.
+    char bytes[8];
   };
   using DataPtr = std::unique_ptr<DataT, decltype(&std::free)>;
 
@@ -137,10 +129,6 @@ struct ValueUnion {
   }
 };
 
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif
-
 ValueUnion GetSysctlImp(std::string const& Name) {
   size_t CurBuffSize = 0;
   if (sysctlbyname(Name.c_str(), nullptr, &CurBuffSize, nullptr, 0) == -1)
@@ -177,7 +165,7 @@ bool GetSysctl(std::string const& Name, std::array<Tp, N>* Out) {
   if (!Buff) return false;
   *Out = Buff.GetAsArray<Tp, N>();
   return true;
-};
+}
 #endif
 
 template <class ArgT>