Re: Shared libraries on IRIX

[Andrej Borsenkow <borsenkow.msk@sni.de>]

On Mon, 10 Feb 1997, Peter Stephenson wrote:

> I hadn't been able to get shared libraries to work on IRIX and I
> think the following, from the dlopen(3) manual, was the problem.
> 
>      Objects loaded by a single invocation of dlopen may import symbols from
>      one another or from any object loaded automatically during program
>      startup, but objects loaded by one dlopen invocation may not directly
>      reference symbols from objects loaded by a different dlopen invocation.
>      Those symbols may, however, be referenced indirectly using dlsym.
>

Yes; this is exactly what happens on my system (Sinix-N 5.42). dlopen()
has a flag (RTLD_GLOBAL) which should make symbols from one module
available for other dlopen() calls. zsh calls dlopen() with RTLD_GLOBAL,
but alas! it forces it to be 0 if not defined.
(Speaking about my system - RTLD_GLOBAL is supported in the next version
first :-(
 
> This fits in with my experiences: problems happen when the zle module
> is loaded, which depends on another module, comp1.  The latter loads
> all right but zle starts acting strangely straight away (the address
> for the init routine is not sensible) and the shell crashes on entry
> to zleread().
> 

Well, I get errors right away - it complaints about no being able to
resolve some symbol from comp1.

> Looking at the code in the light of this, it will make things very
> hard for zle add-on modules even if zle were loaded in one go.  I
> suspect that (for IRIX and perhaps others) it's going to be necessary
> to have zle hard-wired, at least until it's possible to restrict
> modules to a pre-defined set of hooks into zle.
> 

Probably, configure has to check, if RTLD_GLOBAL is defined (is it on
IRIX?). Is there a system, which does _not_ need RTLD_GLOBAL to export
symbols between dlopen() calls?

> Anyway, I added comp1 and zle to modules-bltin by hand and everything
> else seems fine with dynamic loading.  This should therefore become
> the default for IRIX, even with --dynamic; I couldn't see code for it
> in configure.in, though.
> 

What would be fine, is the ability to statically link modules in zsh main
distribution, but still retain dynamic modules feature.

greetings

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Andrej Borsenkow 		Fax:   +7 (095) 252 01 05
SNI ITS Moscow			Tel:   +7 (095) 252 13 88

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