Re: [PATCH] Don't augment LD_LIBRARY_PATH (was Re: [PATCH] do not augment environment)

[Sjoerd van Leent Privé]

Hi Mark,

Just a quick note. Now with GUILE_SYSTEM_EXTENSIONS_PATH, this could be 
very practical when developing a module. However, if a module is already 
present AND is inside SCM_LIB_DIR or SCM_EXTENSIONS_DIR, it would never 
override that situation. I believe there should be a way to be able to 
override the normal behavior.

Regards,
Sjoerd

On 10/03/2012 12:31 PM, Mark H Weaver wrote:
> Hello all,
>
> Here's a preliminary patch to avoid modifying LD_LIBRARY_PATH.
>
> Following Bruce's suggestion, it causes 'sysdep_dynl_link' to manually
> search additional directories if 'lt_dlopenext' fails to find the
> library in the default paths.  However, I took a somewhat different
> approach, and tried to be more careful with regard to portability and
> correctness.
>
> I read the code of libltdl, and mimicked their handling of path
> separators and directory separators, to ensure that this patch will not
> reduce our portability.
>
> I also followed their lead in deciding when to perform a search.  If any
> directory separators are present (even if it's a relative pathname),
> then libltdl does not perform a search.  I used precisely the same
> criterion to decide whether to search additional directories.
>
> So what additional directories does it search?
>
> If GUILE_SYSTEM_EXTENSIONS_PATH is set (even if it's empty), then it
> specifies the additional directories to search.  If it's unset, then the
> default is to search SCM_LIB_DIR and SCM_EXTENSIONS_DIR.
>
> *** Note that this changes the search order in the case where
> GUILE_SYSTEM_EXTENSIONS_PATH is set to a non-empty string.
>
> Currently, a non-empty GUILE_SYSTEM_EXTENSIONS_PATH is passed to
> lt_dladdsearchdir, so it is searched before LTDL_LIBRARY_PATH and
> LD_LIBRARY_PATH, but this patch causes GUILE_SYSTEM_EXTENSIONS_PATH to
> be searched last, to be consistent with the handling of the default
> directories SCM_LIB_DIR and SCM_EXTENSIONS_DIR.  This seems sensible to
> me.  Does anyone see a problem with this change?
>
> This patch also adds robust handling of the case where
> GUILE_SYSTEM_EXTENSIONS_PATH contains more than one path component.
>
> See below for my preliminary patch.  I have not yet tested it carefully.
> It's a context diff, because 'diff' made a mess of the unified diff.
>
> Comments and suggestions solicited.
>
>       Mark