Dear list,
I've been toying around with some problems in the world of dynamic code
loading... (a vast and mythical place). I understand that there is a
fundamental difference between Mach-O executables and Mach-O dynamic libraries
(beyond the obvious Mach-O filetype header). I assume it has to do with a
concept I've read about known as Position Independent Code, in that Dynamic
Libraries are PIC and executables (assuming that they are the first object to
load and therefore could not have to content for a VM address range) are not.
The question goes something like this:
Given I have a Mach-O executable file that contains a symbol that I wish to be
able to call is there any way to use dlopen or NSBundle load to bring those
symbols into another executable?
I have attempted the following two methods:
NSBundle *applicationBundle = [[NSBundle alloc]
initWithFile:@"path/to/mach-o/executable"];
[applicationBundle load]
The above results in:
2010-01-29 10:07:41.812 LoadPagesDynamically[93324:a0f] Attempt to load
executable of a type that cannot be dynamically loaded for CFBundle 0x1001161b0
<path/to/mach-o/executable> (executable, not loaded)
Also:
void* pages_application = dlopen("path/to/mach-o/executable", RTLD_NOW);
The above results in pages_application == NULL with no errors being reported.
If it is not possible (I suspect not), is it possible to convert executable
object code to a PIC representation to be dynamically loaded?
I imagine that there may be something that I don't know given Apple's history
of binary magic (fat binaries, rosetta etc).
It seems that this is a dark corner of the DYLD system that isn't well
documented as to the technical aspects of why this isn't done.
I've tried to be as detailed as possible, but if you would like more
information as to what I've tried, please let me know.
Thanks,
Richard
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