Re: [PATCH] ls-files: don't try to prune an empty index

["René Scharfe" <l.s.r@web.de>]

Am 16.07.2017 um 02:28 schrieb Ramsay Jones:
> 
> 
> On 15/07/17 21:11, René Scharfe wrote:
>> Exit early when asked to prune an index that contains no
>> entries to begin with.  This avoids pointer arithmetic on
>> istate->cache, which is possibly NULL in that case.
>>
>> Found with Clang's UBSan.
>>
>> Signed-off-by: Rene Scharfe <l.s.r@web.de>
>> ---
>>   builtin/ls-files.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/builtin/ls-files.c b/builtin/ls-files.c
>> index b8514a0029..adf572da68 100644
>> --- a/builtin/ls-files.c
>> +++ b/builtin/ls-files.c
>> @@ -362,7 +362,7 @@ static void prune_index(struct index_state *istate,
>>       int pos;
>>       unsigned int first, last;
>>
>> -    if (!prefix)
>> +    if (!prefix || !istate->cache_nr)
>>           return;
>>       pos = index_name_pos(istate, prefix, prefixlen);
>>       if (pos < 0)
> 
> My patch looked like:
> 
> -       if (!prefix)
> +       if (!prefix || !istate->cache || istate->cache_nr == 0)
> 
> ... which is probably a bit 'belt-n-braces'. ;-)

Not checking for !istate->cache at this point is a good thing, I think.
If we have entries, then ->cache must not be NULL, and if it is we'd get
a segfault, notifying us that we have a bug.  We could add an assert to
state this requirement explicitly, but that would be the topic of a
different patch.

René