Update to C++17 and make Config::kControllerIntervalMsecs in… (#791)

Summary:
PyTorch is on C++17 now, so Kineto should be too.

The specific issue was with Config::kControllerIntervalMsecs. This is a static constexpr member - which in pre-C++17 needed a separate namespace definition (i.e. both a declaration `static constexpr chronos::milliseconds kControllerIntervalMsecs` in the class definition and a definition `constexpr chronos::milliseconds Config::kControllerIntervalMsecs`); but after C++17 static constexpr members don't need a separate definition.

Updating to C++17 seems to fix the issue. We could probably remove the `#if __cplusplus < 201703L` handling entirely, but I'm not 100% sure every user of kineto is on C++17

Pull Request resolved: #791

Reviewed By: aaronenyeshi

Differential Revision: D47743393

Pulled By: davidberard98

fbshipit-source-id: a38a8f105344808f239ec3d4da6626b3ffc7c356

libkineto/CMakeLists.txt

@@ -82,17 +82,17 @@ add_custom_target(libkineto_defs.bzl DEPENDS libkineto_defs.bzl)
 add_dependencies(kineto_base libkineto_defs.bzl)
 
 set_target_properties(kineto_base kineto_api PROPERTIES
-      CXX_STANDARD 14
+      CXX_STANDARD 17
       CXX_STANDARD_REQUIRED YES
       CXX_EXTENSIONS NO)
 
 set(KINETO_COMPILE_OPTIONS "-DKINETO_NAMESPACE=libkineto")
 list(APPEND KINETO_COMPILE_OPTIONS "-DFMT_HEADER_ONLY")
 list(APPEND KINETO_COMPILE_OPTIONS "-DENABLE_IPC_FABRIC")
 if(NOT MSVC)
-  list(APPEND KINETO_COMPILE_OPTIONS "-std=c++14")
+  list(APPEND KINETO_COMPILE_OPTIONS "-std=c++17")
 else()
-  list(APPEND KINETO_COMPILE_OPTIONS "/std:c++14")
+  list(APPEND KINETO_COMPILE_OPTIONS "/std:c++17")
   list(APPEND KINETO_COMPILE_OPTIONS "-DWIN32_LEAN_AND_MEAN")
   list(APPEND KINETO_COMPILE_OPTIONS "-DNOGDI")
 endif()

libkineto/src/Config.cpp

@@ -32,7 +32,7 @@ using std::vector;
 
 namespace KINETO_NAMESPACE {
 
-#if __clang__ && __cplusplus < 201703L
+#if __cplusplus < 201703L
 constexpr std::chrono::milliseconds Config::kControllerIntervalMsecs;
 #endif