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Re: Continuing Linux Porting issues

On 07/05/2004 at 1:45 PM, email@hidden wrote:

> If I add an _init symbol to each libaray that I'm going to dlopen (so
> I can dlsym it to force the library to initialize itself) it works
> pretty good EXCEPT if I have cross-library dependencies, then I get
> problems with multiply defined _init symbols. ie: if libfoo.dylib
> depends on libbar.dylib then I link libfoo.dylib with -lbar and get a
> multiply defined _init symbol.
>
> I'm currently thinking about putting a unique symbol in each library
> (ie: _init_foo, _init_bar) but this seems like a really nasty way to
> solve the problem. Is there something better? Either a way to get
> around the multiply defined symbols or some existing symbol in each
> library I can lookup?

Yes, this is a really nasty way to solve the problem. It is also
exactly how I chose to solve the problem :) My build system
automatically code generates a file that contains a function whose name
is derived from the name of the dynamic library (e.g., _foo) and
compiles this file into the dynamic library. With this approach, you
shouldn't have to modify your 100 or so libraries, just your build
system.

> Greg Corson wrote:
>
>> The main implementation problem I have is that there is no common
>> symbol in all of my .dylib files to lookup. I really don't want to
>> add code to put, say, an _init and associated #ifdef OSX kind of code
>> into all 100 or so libraries. Is there some symbol guaranteed to be
>> in every library that I could lookup with dlsym? (or some way to add
>> one from the command line during compile/link?)

I'm not aware of a symbol that is available from every library. In
fact, if there was one, you would get multiply defined symbol errors
like you previously mentioned.

>> I tried dumping the libraries with otool and found a few common
>> symbols like ___initialize_Cplusplus, __dyld_func_lookup and the
>> (supposedly) linker defined symbol __mh_dylib_header but dlsym
>> couldn't find any of these (maybe they are not exported?)

I don't believe these symbols are exported. The nm tool is helpful to
determine which symbols are exported from your dynamic library.
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 >Re: Continuing Linux Porting issues (From: email@hidden)



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