Issue #73 Fix missing STL DLL export warnings of Visual Studio according to KB168958.

src/gflags.h.in

@@ -85,6 +85,14 @@
 #include "gflags_declare.h" // IWYU pragma: export
 
 
+// Export/import STL instantiations used as data members of exported classes
+// \sa http://support.microsoft.com/default.aspx?scid=KB;EN-US;168958
+#ifdef GFLAGS_EXTERN_STL
+  GFLAGS_EXTERN_STL template class GFLAGS_DLL_DECL std::allocator<char>;
+  GFLAGS_EXTERN_STL template class GFLAGS_DLL_DECL std::basic_string<char>;
+#endif
+
+
 namespace GFLAGS_NAMESPACE {
 
 

src/gflags_config.h.in

@@ -43,5 +43,15 @@
 #  define GFLAGS_DLL_DEFINE_FLAG
 #endif
 
+// Export/import of STL class instantiations
+// \sa http://support.microsoft.com/default.aspx?scid=KB;EN-US;168958
+#if defined(GFLAGS_SHARED_LIBS) && defined(_MSC_VER) && _MSC_VER >= 1100
+#  ifdef GFLAGS_DLL_EXPORT
+#    define GFLAGS_EXTERN_STL
+#  else
+#    define GFLAGS_EXTERN_STL extern
+#  endif
+#endif
+
 
 #endif // GFLAGS_GFLAGS_CONFIG_H_
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