diff --git a/src/haiku.cpp b/src/haiku.cpp
index e55b0b13..6ede53d9 100644
--- a/src/haiku.cpp
+++ b/src/haiku.cpp
@@ -17,8 +17,12 @@
     You should have received a copy of the GNU General Public License
     along with Grafx2; if not, see <http://www.gnu.org/licenses/>
 */
-#include "struct.h"
-
+/** @file haiku.cpp
+ * Definition of Haiku specific functions.
+ *
+ * Haiku API is C++, so this is C++ code exporting as C symbols
+ * to be called by GrafX2 C code.
+ */
 #ifdef __HAIKU__
 #include <Clipboard.h>
 #include <Entry.h>
@@ -26,8 +30,7 @@
 
 #include <string.h>
 
-extern "C" qword haiku_get_free_space(char* path);
-extern "C" char* haiku_get_clipboard();
+#include "haiku.h"
 
 qword haiku_get_free_space(char* path)
 {
@@ -38,6 +41,9 @@ qword haiku_get_free_space(char* path)
 	return (qword) disk.Capacity();	
 }
 
+/**
+ * @return NULL or a string that should be free()'d by the caller
+ */
 char* haiku_get_clipboard()
 {
 	if (be_clipboard->Lock())
diff --git a/src/haiku.h b/src/haiku.h
index 781e2b86..c23fb940 100644
--- a/src/haiku.h
+++ b/src/haiku.h
@@ -1,15 +1,21 @@
-#include "struct.h"
-
-/*
+/** @file haiku.h
+ * Declarations of HAIKU specific functions.
+ *
  * Haiku specific code was moved here, because the API is C++.
  * It can't be compiled in the usual C files.
- * So we provide a C wrapper to the functons we need.
+ * So we provide a C wrapper to the functions we need.
  */
-
 #ifndef __HAIKU_H
 #define __HAIKU_H
+#include "struct.h"
 
+#ifdef __cplusplus
+extern "C" {
+#endif
 qword haiku_get_free_space(char* path);
 char* haiku_get_clipboard();
+#ifdef __cplusplus
+}
+#endif
 
 #endif
diff --git a/tools/Doxyfile b/tools/Doxyfile
index e0b39c66..1d2ea574 100644
--- a/tools/Doxyfile
+++ b/tools/Doxyfile
@@ -1974,7 +1974,7 @@ INCLUDE_FILE_PATTERNS  =
 # recursively expanded use the := operator instead of the = operator.
 # This tag requires that the tag ENABLE_PREPROCESSING is set to YES.
 
-PREDEFINED             = __attribute__(x)=
+PREDEFINED             = __attribute__(x)= __HAIKU__
 
 # If the MACRO_EXPANSION and EXPAND_ONLY_PREDEF tags are set to YES then this
 # tag can be used to specify a list of macro names that should be expanded. The