Re: How to manually register a symbol address in dyld?
Re: How to manually register a symbol address in dyld?
- Subject: Re: How to manually register a symbol address in dyld?
- From: Peter O'Gorman <email@hidden>
- Date: Wed, 14 Oct 2009 09:40:38 -0500
On 10/14/2009 08:56 AM, Stéphane Corthésy wrote:
Hello,
On Oct 13, 2009, at 4:30 PM, Peter O'Gorman wrote:
On 10/13/2009 02:55 AM, Stéphane Corthésy wrote:
Hello,
For some reason (that I'll explain later), I need to load a bundle which
contains symbols undefined in application libraries. BUT, though these
symbols are undefined, the actual implementations are present in current
runtime, but under a different symbol. Thus, before loading that bundle
I need to manually tell dyld that symbol 'my_renamed_function' should be
bound to 'my_original_function' already present in system libraries. Or
I need a hook that would allow me to do that while loading the bundle.
I'm working on 10.6. I tried to look at dyld source code, but got
lost :-)
I tried to use NSInstallLinkEditErrorHandlers, but my handler wasn't
invoked.
So, is there a way to do that, and how?
Why do you need to do this? There are very likely alternative ways of
doing what you need e.g.
weak undefined external symbols,
That cannot work. As I wrote, the bundle (already weakly linked) has
symbols that are not available on 10.6 (they were on 10.5), BUT though
the symbols are not exported, the actual functions are available in
10.6, thus I'd like to create a bundle which would augment dyld symbol
table and then load the other bundle with (previously unknown) symbols,
and it would link well.
I am still unsure what you're trying to fix. If I am reading this right,
the bundle is using OS symbols that were global and exported in 10.5,
but have become local symbols in 10.6, and you want it to keep using
them (because you're using a third party plugin and you don't have
access to the source code?).
You could certainly load a library on 10.6 (or use
DYLD_INSERT_LIBRARIES) that provides functions with the names your
plugin uses, goes through the symbol tables looking for the address of
the local-on-10.6 symbols, and calls them. How to do that is documented
in the header files in /usr/include/mach-o and on developer.apple.com.
However, if you have access to the source code for the bundle, then I
suggest fixing it so that it does not require private symbols.
Peter
--
Peter O'Gorman
http://pogma.com
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