Re: How to tell whether an executable supports GC?
Re: How to tell whether an executable supports GC?
- Subject: Re: How to tell whether an executable supports GC?
- From: "Chris Suter" <email@hidden>
- Date: Fri, 8 Aug 2008 15:18:26 +1000
On Fri, Aug 8, 2008 at 2:48 PM, André Pang <email@hidden> wrote:
> Hi all, is there a reasonably easy way to programmatically determine
> whether a particular executable on-disk supports garbage collection? Cocoa
> methods aren't necessary; all C functions are welcome. Poking around in an
> executable's Mach-O headers is fine too, but I'm not sure what to look for.
>
> My usage scenario is that we're intending to ship an experimental GC
> version of our app to some customers, but we have a lot of plugins for our
> app, and they won't work under the GC version unless they're compiled
> GC-supported. I'd like to display a sheet in the regular, non-GC version of
> the app that tells the user which plugins aren't GC-supported, so I can't
> simply attempt to preflight the bundle and see if that fails, since the
> preflight check would be running on the non-GC version. Any hints?
>
You want to look at the __image_info section in the __OBJC segment:
struct objc_image_info {
uint32_t version; // initially 0
uint32_t flags;
};
#define OBJC_IMAGE_SUPPORTS_GC 2
#define OBJC_IMAGE_GC_ONLY 4
Have a look at the linker source code in MachOReaderDylib.hpp. You'll have
to check what needs to be swapped.
I don't know if there's an easier way of figuring it out.
-- Chris
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