Re: Error reporting should be improved

[Peter Rosin]

Den 2009-12-30 06:39 skrev Bob Friesenhahn:
> On Wed, 30 Dec 2009, Peter Rosin wrote:
> > The thread safety thing can be ignored as libltdl isn't thread safe
> > and needs to be mutexed anyway. Care to test this patch?
>
> There used to be some useless effort to make it thread safe. Apparently 
> that is gone now.  Regardless, there is also a potential re-entrancy 
> issue, which could be encountered if a legacy OS interface is supported 
> (re-implemented) via dlopen() or if some other implementation logic 
> (e.g. lazy symbol resolution) uses dlsym().

I can't say that I understand what you are describing, but dlerror need
not be reentrant[1], and we do various manipulations of internal state
during lt_dlopen etc, so I don't see how any argument about reentrancy
can hold. What am I missing this time?

[1] http://www.opengroup.org/onlinepubs/009695399/functions/dlerror.html

> An alternative approach would be to store loader-specific errors in 
> loader-specific storage and iterate through the loaders in order to 
> obtain their error messages.

That is outside the scope of the provided patch.

> With this patch, how will the accumulated error strings be reported to 
> the API user? Some of the error reports will be useless and so it may 
> not be useful to combine them since a useless report would have the same 
> significance as an important one.  The origin (id of the reporting 
> loader) would be useful to record.  If the origin was part of the string 
> (or the string is owned by the loader) then that would serve to keep 
> them distinct.

This patch does of course not address the original issue, it only
addresses the issue with dlerror returning a string to the ltdl user
that might have a limited life span.

> Unfortunately, lt_dladderror() is publically exposed so it is difficult 
> to change its arguments even though it is not documented.

This patch does not change lt_dladderror in a way that I classify as
significant. Do you disagree?

I have not found anything in your message that "kills" the patch, but
yet I get the feeling that you do not like it, and I would like to know
what you think is wrong with it...

Cheers,
Peter