From 754d3329a652ea0f1306e985a6e1bb0245275176 Mon Sep 17 00:00:00 2001
From: Andreas Schuh <aschuh@heartflow.com>
Date: Mon, 15 Oct 2018 00:22:36 -0700
Subject: [PATCH] fix: No extern template declaration for MSVC <12.0

---
 .gitignore      |  1 +
 src/gflags.h.in | 12 ++++++++----
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/.gitignore b/.gitignore
index 321f70e..706f7f8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -2,6 +2,7 @@
 /build/
 /builds/
 /build-*/
+/_build/
 .DS_Store
 CMakeCache.txt
 DartConfiguration.tcl
diff --git a/src/gflags.h.in b/src/gflags.h.in
index b437862..7b218b9 100644
--- a/src/gflags.h.in
+++ b/src/gflags.h.in
@@ -442,10 +442,14 @@ class GFLAGS_DLL_DECL FlagRegisterer {
 };
 
 // Force compiler to not generate code for the given template specialization.
-#define GFLAGS_DECLARE_FLAG_REGISTERER_CTOR(type)                  \
-  extern template GFLAGS_DLL_DECL FlagRegisterer::FlagRegisterer(  \
-      const char* name, const char* help, const char* filename,    \
-      type* current_storage, type* defvalue_storage)
+#if defined(_MSC_VER) && _MSC_VER < 1800 // Visual Studio 2013 version 12.0
+  #define GFLAGS_DECLARE_FLAG_REGISTERER_CTOR(type)
+#else
+  #define GFLAGS_DECLARE_FLAG_REGISTERER_CTOR(type)                  \
+    extern template GFLAGS_DLL_DECL FlagRegisterer::FlagRegisterer(  \
+        const char* name, const char* help, const char* filename,    \
+        type* current_storage, type* defvalue_storage)
+#endif
 
 // Do this for all supported flag types.
 GFLAGS_DECLARE_FLAG_REGISTERER_CTOR(bool);