in the Java binding mark all internal functions as hidden

src/runtime/java/jni_utils.h

@@ -1,31 +1,44 @@
 #ifndef JNI_UTILS
 #define JNI_UTILS
 
+#if defined(_MSC_VER)
+
+#define JPGF_INTERNAL_DECL
+#define JPGF_INTERNAL
+
+#else
+
+#define JPGF_INTERNAL_DECL  __attribute__ ((visibility ("hidden")))
+#define JPGF_INTERNAL       __attribute__ ((visibility ("hidden")))
+
+#endif
+
+
 #define l2p(x) ((void*) (intptr_t) (x))
 #define p2l(x) ((jlong) (intptr_t) (x))
 
-jstring
+JPGF_INTERNAL_DECL jstring
 gu2j_string(JNIEnv *env, GuString s);
 
-jstring
+JPGF_INTERNAL_DECL jstring
 gu2j_string_buf(JNIEnv *env, GuStringBuf* sbuf);
 
-GuString
+JPGF_INTERNAL_DECL GuString
 j2gu_string(JNIEnv *env, jstring s, GuPool* pool);
 
-size_t
+JPGF_INTERNAL_DECL size_t
 gu2j_string_offset(GuString s, size_t offset);
 
-size_t
+JPGF_INTERNAL_DECL size_t
 j2gu_string_offset(GuString s, size_t joffset);
 
-void*
+JPGF_INTERNAL_DECL void*
 get_ref(JNIEnv *env, jobject self);
 
-void
+JPGF_INTERNAL_DECL void
 throw_jstring_exception(JNIEnv *env, const char* class_name, jstring msg);
 
-void
+JPGF_INTERNAL_DECL void
 throw_string_exception(JNIEnv *env, const char* class_name, const char* msg);
 
 #endif