Add __declspec(dllexport) to class Node and class Op if build on Wind… (#296)

* Add __declspec(dllexport) to class Node and class Op if build on Windows, so that it can be referenced in some test code in MXNet

* correct typo

* reuse the macro in c_api.h

* revert changes on base.h

* one more place to revert

* use enclosing extern c block

* revert a change caused by copy

* remove a space

nnvm/include/nnvm/c_api.h

@@ -8,21 +8,15 @@
 #ifndef NNVM_C_API_H_
 #define NNVM_C_API_H_
 
-#ifdef __cplusplus
-#define NNVM_EXTERN_C extern "C"
-#else
-#define NNVM_EXTERN_C
-#endif
-
 /*! \brief NNVM_DLL prefix for windows */
 #ifdef _WIN32
 #ifdef NNVM_EXPORTS
-#define NNVM_DLL NNVM_EXTERN_C __declspec(dllexport)
+#define NNVM_DLL __declspec(dllexport)
 #else
-#define NNVM_DLL NNVM_EXTERN_C __declspec(dllimport)
+#define NNVM_DLL __declspec(dllimport)
 #endif
 #else
-#define NNVM_DLL NNVM_EXTERN_C
+#define NNVM_DLL
 #endif
 
 /*! \brief manually define unsigned int */
@@ -35,6 +29,9 @@ typedef void *SymbolHandle;
 /*! \brief handle to Graph */
 typedef void *GraphHandle;
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 /*!
  * \brief Set the last error message needed by C API
  * \param msg The error message to set.
@@ -384,4 +381,8 @@ NNVM_DLL int NNGraphApplyPasses(GraphHandle src,
                                 const char** pass_names,
                                 GraphHandle *dst);
 
+#ifdef __cplusplus
+} /* end extern "C" */
+#endif
+
 #endif  // NNVM_C_API_H_

nnvm/include/nnvm/node.h

@@ -12,6 +12,7 @@
 #include <unordered_map>
 #include "./base.h"
 #include "./op.h"
+#include "./c_api.h"
 
 namespace nnvm {
 
@@ -94,7 +95,7 @@ struct NodeAttrs {
 /*!
  * \brief Node represents an operation in a computation graph.
  */
-class Node {
+class NNVM_DLL Node {
  public:
   /*! \brief The attributes in the node. */
   NodeAttrs attrs;

nnvm/include/nnvm/op.h

@@ -14,6 +14,7 @@
 #include <limits>
 #include <functional>
 #include "./base.h"
+#include "./c_api.h"
 
 namespace nnvm {
 
@@ -81,7 +82,7 @@ static const uint32_t kVarg = std::numeric_limits<uint32_t>::max();
  * }
  * \endcode
  */
-class Op {
+class NNVM_DLL Op {
  public:
   /*! \brief name of the operator */
   std::string name;