Re: [PATCH] list-objects: perform NULL check before the variable is dereferenced

Nguyen Thai Ngoc Duy [off-list ref] writes:

2012/4/10 Junio C Hamano [off-list ref]:

quoted

Nguyễn Thái Ngọc Duy  [off-list ref] writes:

quoted

Signed-off-by: Nguyễn Thái Ngọc Duy <redacted>
---
 list-objects.c |   10 ++++++----
 1 files changed, 6 insertions(+), 4 deletions(-)

Please explain why this is needed?

I can see that process_blob() is called from process_tree() which passes
the return value from lookup_blob(entry.sha1) directly without looking at
it.  lookup_blob() can issue an error message and return NULL if there is
a SHA-1 collision with an object that is not a blob.

to avoid segmentation fault in that case, if "blob" is NULL, it dies
at blob->object anyway and the check "if (!obj)" is useless.

Well, I didn't mean that you should explain whatever to _me_ as a
response; I meant that the log message should explain that to future
readers. I thought you have been here long enough to know that ;-)

Also "check NULL before dereferencing" means "avoid segmentation fault",
so that is not the primary thing that needs to be explained.  The point is
to explain why and how a NULL could come into the codepath in the first
place.

Please try again when post 1.7.10 cycle opens.

Thanks.