Set up visibility on OS X. This seems to work...

darwin/GNUmakeinc.mk

@@ -20,8 +20,13 @@ osMFILES = \
 osHFILES = \
 	darwin/uipriv_darwin.h
 
-osCFLAGS = -mmacosx-version-min=10.7 -DMACOSX_DEPLOYMENT_TARGET=10.7
-osLDFLAGS = -mmacosx-version-min=10.7 -lobjc -framework Foundation -framework AppKit
+osCFLAGS = \
+	-D_UI_EXTERN='__attribute__((visibility("default"))) extern' \
+	-fvisibility=hidden \
+	-mmacosx-version-min=10.7 -DMACOSX_DEPLOYMENT_TARGET=10.7
+osLDFLAGS = \
+	-fvisibility=hidden \
+	-mmacosx-version-min=10.7 -lobjc -framework Foundation -framework AppKit
 
 # the gcc flags don't work with Apple's linker
 # fortunately, we don't need any; Apple's linker warns about undefined symbols in -shared builds!

ui_darwin.h

@@ -11,10 +11,10 @@ This file assumes that you have imported <Cocoa/Cocoa.h> and "ui.h" beforehand.
 // The second parameter should come from [RealControlType class].
 // The two scrollView parameters allow placing scrollbars on the new control.
 // The two onDestroy parameters define a function and its parameter to call when the widget is destroyed.
-extern void uiDarwinMakeControl(uiControl *c, Class class, BOOL inScrollView, BOOL scrollViewHasBorder, void (*onDestroy)(void *), void *onDestroyData);
+_UI_EXTERN void uiDarwinMakeControl(uiControl *c, Class class, BOOL inScrollView, BOOL scrollViewHasBorder, void (*onDestroy)(void *), void *onDestroyData);
 
 // You can use this function from within your control implementations to return text strings that can be freed with uiFreeText().
-extern char *uiDarwinNSStringToText(NSString *);
+_UI_EXTERN char *uiDarwinNSStringToText(NSString *);
 
 struct uiSizingSys {
 	// this structure currently left blank