SEGV when lookup_* returns NULL

SEGV when lookup_* returns NULL

[Martin Waitz]

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hoi :)

When trying to an unmodified GIT on a repository with submodules
it segfaults a lot.

All the lookup_{blob,tree,commit} functions check that the object
really is of the requested type and return NULL otherwise.
However this NULL pointer is not checked in the calling functions.

Should we make lookup_* to just die when invoked on another object-type?
Or modify all the callers?
Is there a sane error-handling strategy besides dying in this case?
Really checking all the return values in the whole chain would be
a lot of work.

-- 
Martin Waitz

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Re: SEGV when lookup_* returns NULL

[Junio C Hamano]

Martin Waitz <tali@admingilde.org> writes:

> All the lookup_{blob,tree,commit} functions check that the object
> really is of the requested type and return NULL otherwise.
> However this NULL pointer is not checked in the calling functions.
>
> Should we make lookup_* to just die when invoked on another object-type?

Making lookup_{specific type} die when they see unexpected type
would not hurt that much, I think, aside from the possibility
that some callers may check NULL to see if object already
exists, but they should be using has_sha1_file() instead.

Re: SEGV when lookup_* returns NULL

[Johannes Schindelin]

Hi,

On Mon, 27 Nov 2006, Junio C Hamano wrote:

> Martin Waitz <tali@admingilde.org> writes:
> 
> > All the lookup_{blob,tree,commit} functions check that the object
> > really is of the requested type and return NULL otherwise.
> > However this NULL pointer is not checked in the calling functions.
> >
> > Should we make lookup_* to just die when invoked on another object-type?
> 
> Making lookup_{specific type} die when they see unexpected type
> would not hurt that much, I think, aside from the possibility
> that some callers may check NULL to see if object already
> exists, but they should be using has_sha1_file() instead.

And it would totally clobber the long term goal of libifying git.

Ciao,
Dscho

Re: SEGV when lookup_* returns NULL

[Junio C Hamano]

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> And it would totally clobber the long term goal of libifying git.

Why?  You would certainly install your own die() handler by that
time I presume?

Re: SEGV when lookup_* returns NULL

[Morten Welinder]

> Why?  You would certainly install your own die() handler by that
> time I presume?

Likely, but short of exiting or using longjmp/setjmp what can you do
in such a "die"?  Not much.  And most GUI users will be unhappy
with the exit approach.

If there is any chance that the error is not the programmer's fault, a
nice library ought to pass the error back somehow.