Tracing message sends in Objective-C

Update: It turns it there's a much easier, more reliable way to see every Objective-C message send. So ignore the rest of this post and read about NSObjCMessageLoggingEnabled in TN2124.

So now I'm trying to get bindings working when I put my NSCell subclass in a table column. It appears, for the standard NSCell subclasses, that NSTableColumn looks at the subclass's exposed bindings and re-exposes them on itself. However, it's not doing that for my NSCell subclass's bindings.

So, I want to trace the messages that are flying around inside Interface Builder to see if I can figure out how NSTableColumn decides what bindings to expose. Ideally I'd have a little dynamic library with a logging version of objc_msgSend and I could get Interface Builder to run using that. I don't have that (yet). I found this old Usenet post from a NeXT engineer showing how to trace objc_msgSend using GDB. That will be much slower than smashing in a logging version of objc_msgSend, but it's better than nothing.

Of course, the GDB command in that Usenet post is for NEXTSTEP running on Intel. It'll probably work on MacOS X running on Intel, but my Powerbook has a PowerPC processor. Also, Apple introduced a new message-send function in Tiger, so you have to set two breakpoints. These commands work on MacOS X on PowerPC:

b objc_msgSend
comm
silent
printf "%c[%s %s]\n", $r3&&((id)$r3)->isa->info&2?'+':'-', $r3?((id)$r3)->isa->name:"nil", $r4
cont
end
b objc_msgSend_rtp
comm
silent
printf "%c[%s %s]\n", $r3&&((id)$r3)->isa->info&2?'+':'-', $r3?((id)$r3)->isa->name:"nil", $r4
cont
end

Here's some sample output from GDB, tracing the first few messages sent in -[NSObject exposedBindings]:

-[NSTableColumn _bindingAdaptor]
+[NSBinder binderClassesForObject:]
+[NSBinder _allBinderClasses]
+[NSDisplayPatternTitleBinder isUsableWithObject:]
+[NSBox self]
-[NSTableColumn isKindOfClass:]
+[NSWindow self]
-[NSTableColumn isKindOfClass:]
+[NSWindowTemplate self]
-[NSTableColumn isKindOfClass:]
+[NSTableBinder isUsableWithObject:]
+[NSTableView self]
-[NSTableColumn isKindOfClass:]
+[NSObjectParameterBinder isUsableWithObject:]
+[NSObjectParameterBinder binderClassesSuperseded]
+[NSArray array]
+[NSArray allocWithZone:]