Fixed the compiler errors. The Mac OS X Listboxes are created!... but don't show any items. Let's figure out why.

bleh_darwin.m

@@ -28,11 +28,21 @@ id *_NSObservedObjectKey = (id *) (&NSObservedObjectKey);
 NSUInteger is listed as being in <objc/NSObjCRuntime.h>... which doesn't exist. Rather than relying on undocumented header file locations or explicitly typedef-ing NSUInteger to the (documented) unsigned long, I'll just place things here for maximum safety. I use uintptr_t as that should encompass every possible unsigned long.
 */
 
+uintptr_t objc_msgSend_uintret_noargs(id obj, SEL sel)
+{
+	return (uintptr_t) ((NSUInteger) objc_msgSend(obj, sel));
+}
+
 id _objc_msgSend_uint(id obj, SEL sel, uintptr_t a)
 {
 	return objc_msgSend(obj, sel, (NSUInteger) a);
 }
 
+id objc_msgSend_id_uint(id obj, SEL sel, id a, uintptr_t b)
+{
+	return objc_msgSend(obj, sel, a, (NSUInteger) b);
+}
+
 /*
 same as above, but for NSInteger
 */
@@ -119,7 +129,8 @@ struct xsize objc_msgSend_stret_size_noargs(id obj, SEL sel)
 This is a doozy: it deals with a NSUInteger array needed for this one selector, and converts them all into a uintptr_t array so we can use it from Go. The two arrays are created at runtime with malloc(); only the NSUInteger one is freed here, while Go frees the returned one. It's not optimal.
 */
 
-static SEL getIndexes = sel_getUid("getIndexes:maxCount:inRange:");
+static SEL getIndexes;
+static BOOL getIndexes_init = NO;		/* because we can't initialize it out here */
 
 uintptr_t *NSIndexSetEntries(id indexset, uintptr_t count)
 {
@@ -128,6 +139,10 @@ uintptr_t *NSIndexSetEntries(id indexset, uintptr_t count)
 	uintptr_t i;
 	size_t countsize;
 
+	if (getIndexes_init == NO) {
+		getIndexes = sel_getUid("getIndexes:maxCount:inRange:");
+		getIndexes_init = YES;
+	}
 	countsize = (size_t) count;
 	nsuints = (NSUInteger *) malloc(countsize * sizeof (NSUInteger));
 	/* TODO check return value */

listbox_darwin.go

@@ -2,7 +2,7 @@
 package ui
 
 import (
-	"runtime"
+	"reflect"
 	"unsafe"
 )
 
@@ -15,7 +15,10 @@ PERSONAL TODO - make a post somewhere that does all this in Objective-C itself,
 */
 
 // #cgo LDFLAGS: -lobjc -framework Foundation -framework AppKit
+// #include <stdlib.h>
 // #include "objc_darwin.h"
+// /* cgo doesn't like nil */
+// id nilid = nil;
 import "C"
 
 /*
@@ -89,12 +92,12 @@ func appendListboxArray(array C.id, what string) {
 }
 
 func insertListboxArrayBefore(array C.id, what string, before int) {
-	objc_msgSend_id_uint(array, _insertObjectAtArrangedObjectsIndex,
+	C.objc_msgSend_id_uint(array, _insertObjectAtArrangedObjectsIndex,
-		toListboxItem(what), uintptr(before))
+		toListboxItem(what), C.uintptr_t(before))
 }
 
 func deleteListboxArray(array C.id, index int) {
-	objc_msgSend_id(array, _removeObjectAtArrangedObjectsIndex, uintptr(index))
+	objc_msgSend_uint(array, _removeObjectAtArrangedObjectsIndex, uintptr(index))
 }
 
 func indexListboxArray(array C.id, index int) string {
@@ -133,7 +136,7 @@ func bindListboxArray(tableColumn C.id, array C.id) {
 	C.objc_msgSend_id_id_id_id(tableColumn, _bindToObjectWithKeyPathOptions,
 		tableColumnBinding,
 		array, listboxItemKeyPath,
-		C.id(C.nil))			// no options
+		C.nilid)				// no options
 }
 
 func listboxArray(tableColumn C.id) C.id {
@@ -194,19 +197,19 @@ func makeListbox(parentWindow C.id, alternate bool) C.id {
 	}
 	C.objc_msgSend_bool(listbox, _setAllowsMultipleSelection, multi)
 	C.objc_msgSend_bool(listbox, _setAllowsEmptySelection, C.BOOL(C.YES))
-	C.objc_msgSend_id(listbox, _setHeaderView, C.id(C.nil))
+	C.objc_msgSend_id(listbox, _setHeaderView, C.nilid)
 	// TODO others?
 	windowView := C.objc_msgSend_noargs(parentWindow, _contentView)
 	C.objc_msgSend_id(windowView, _addSubview, listbox)
 	return listbox
 }
 
-func appendListbox(listbox C.id, what string) {
+func appendListbox(listbox C.id, what string, alternate bool) {
 	array := listboxArray(listboxTableColumn(listbox))
 	appendListboxArray(array, what)
 }
 
-func insertListboxBefore(listbox C.id, what string, before int) {
+func insertListboxBefore(listbox C.id, what string, before int, alternate bool) {
 	array := listboxArray(listboxTableColumn(listbox))
 	insertListboxArrayBefore(array, what, before)
 }
@@ -215,24 +218,24 @@ func insertListboxBefore(listbox C.id, what string, before int) {
 // C.NSIndexSetEntries() makes two arrays of size count: one NSUInteger array and one C.uintptr_t array for returning; this makes a third of type []int for using
 // if only NSUInteger was usable (see bleh_darwin.m)
 func selectedListboxIndices(listbox C.id) (list []int) {
-	var cindices []C.uintptr
+	var cindices []C.uintptr_t
 
 	indices := C.objc_msgSend_noargs(listbox, _selectedRowIndexes)
-	count := int(C.objc_msgSend_uintret(indices, _count))
+	count := int(C.objc_msgSend_uintret_noargs(indices, _count))
 	if count == 0 {
-		ret
+		return nil
 	}
 	list = make([]int, count)
 	cidx := C.NSIndexSetEntries(indices, C.uintptr_t(count))
-	defer C.free(cidx)
+	defer C.free(unsafe.Pointer(cidx))
 	pcindices := (*reflect.SliceHeader)(unsafe.Pointer(&cindices))
 	pcindices.Cap = count
 	pcindices.Len = count
-	pcindices.Data = uintptr(cidx)
+	pcindices.Data = uintptr(unsafe.Pointer(cidx))
 	for i := 0; i < count; i++ {
-		indices[i] = int(cidx[i])
+		list[i] = int(cindices[i])
 	}
-	return indices
+	return list
 }
 
 func selectedListboxTexts(listbox C.id) (texts []string) {

objc_darwin.h

@@ -47,6 +47,8 @@ struct xsize {
 
 extern struct xsize objc_msgSend_stret_size_noargs(id obj, SEL sel);
 
+extern uintptr_t objc_msgSend_uintret_noargs(id objc, SEL sel);
+
 extern intptr_t objc_msgSend_intret_noargs(id obj, SEL sel);
 
 #define m1(name, type1) \
@@ -85,12 +87,14 @@ extern id objc_msgSend_int(id obj, SEL sel, intptr_t a);
 m2(id_id, id, id)
 extern id _objc_msgSend_rect_bool(id obj, SEL sel, int64_t x, int64_t y, int64_t w, int64_t h, BOOL b);
 extern id objc_msgSend_id_int(id obj, SEL sel, id a, intptr_t b);
+extern id objc_msgSend_id_uint(id obj, SEL sel, id a, uintptr_t b);
 
 m3(id_id_id, id, id, id)
 m3(sel_id_bool, SEL, id, BOOL)
 
 extern id _objc_msgSend_rect_uint_uint_bool(id obj, SEL sel, int64_t x, int64_t y, int64_t w, int64_t h, uintptr_t b, uintptr_t c, BOOL d);
 m4(id_sel_id_id, id, SEL, id, id)
+m4(id_id_id_id, id, id, id, id)
 
 /* for listbox_darwin.go */
 extern uintptr_t *NSIndexSetEntries(id, uintptr_t);