Compile OpenCV with GCC visibility set to hidden

modules/core/include/opencv2/core/cvdef.h

@@ -73,8 +73,10 @@
 #  define CV_ENABLE_UNROLLED 1
 #endif
 
-#if (defined WIN32 || defined _WIN32 || defined WINCE) && defined CVAPI_EXPORTS
+#if (defined WIN32 || defined _WIN32 || defined WINCE || defined __CYGWIN__) && defined CVAPI_EXPORTS
 #  define CV_EXPORTS __declspec(dllexport)
+#elif defined __GNUC__ && __GNUC__ >= 4
+#  define CV_EXPORTS __attribute__ ((visibility ("default")))
 #else
 #  define CV_EXPORTS
 #endif

modules/core/include/opencv2/core/cvstd.hpp

@@ -174,7 +174,7 @@ public:
   To make it all work, you need to specialize Ptr<>::delete_obj(), like:
 
   \code
-  template<> void Ptr<MyObjectType>::delete_obj() { call_destructor_func(obj); }
+  template<> CV_EXPORTS void Ptr<MyObjectType>::delete_obj() { call_destructor_func(obj); }
   \endcode
 
   \note{if MyObjectType is a C++ class with a destructor, you do not need to specialize delete_obj(),

modules/core/include/opencv2/core/types_c.h

@@ -272,7 +272,11 @@ CV_INLINE double cvRandReal( CvRNG* rng )
 #define IPL_BORDER_REFLECT    2
 #define IPL_BORDER_WRAP       3
 
-typedef struct CV_EXPORTS _IplImage
+typedef struct
+#ifdef __cplusplus
+  CV_EXPORTS
+#endif
+_IplImage
 {
     int  nSize;             /* sizeof(IplImage) */
     int  ID;                /* version (=0)*/
@@ -563,7 +567,11 @@ CV_INLINE int cvIplDepth( int type )
 #define CV_MAX_DIM            32
 #define CV_MAX_DIM_HEAP       1024
 
-typedef struct CV_EXPORTS CvMatND
+typedef struct
+#ifdef __cplusplus
+  CV_EXPORTS
+#endif
+CvMatND
 {
     int type;
     int dims;
@@ -610,7 +618,11 @@ CvMatND;
 
 struct CvSet;
 
-typedef struct CV_EXPORTS CvSparseMat
+typedef struct
+#ifdef __cplusplus
+  CV_EXPORTS
+#endif
+CvSparseMat
 {
     int type;
     int dims;