Re: avoiding access to NULL pointers coming from user customizations?

[Patrice Dumas]

On Sat, May 04, 2024 at 08:54:15PM +0100, Gavin Smith wrote:
> In my opinion it is an issue as it should not be possible to cause a
> segfault purely with Perl code.  If there is a segfault this points towards
> a bug in XS/C code.  If the user provides customization code that is purely
> in Perl it would be very surprising for this to cause a segfault.  The
> customization API should be more robust than this.

It is not really a lack of robustness if it is done on purpose. Also it
should not be so surprising as it would be some quite specific code
that triggers a segfault.  That being said, I agree that user-defined
code being only Perl, even if in unusual situations, having a segfault
would be unexpected.

> Without knowing much about the customization API I don't know the best
> way to protect against this kind of situation but some possibilities are
> to check for null pointers when accessing cutomization variable values

That's the easiest, the only issue is that it complexifies a little and
slows the code.  I'll do that.

> in C, or to disable setting customization variables after this step:
> "some customization variables are reset before the conversion to strings
> if they are undef".  If user code attempts to do this the program could
> exit with an error.

I prefer avoiding more complexity on that part.

-- 
Pat