Re: [PATCH v2 03/10] mailmap: remove email copy and length limitation

[Junio C Hamano <gitster@pobox.com>]

Antoine Pelisse <apelisse@gmail.com> writes:

>> +static struct string_list_item *lookup_prefix(struct string_list *map,
>> +                                             const char *string, size_t len)
>> +{
>> +       int i = string_list_find_insert_index(map, string, 1);
>> +       if (i < 0) {
>> +               /* exact match */
>> +               i = -1 - i;
>> +               /* does it match exactly? */
>> +               if (!map->items[i].string[len])
>> +                       return &map->items[i];
>
> I'm not sure the condition above is necessary, as I don't see why an
> exact match would not be an exact match.

You have a overlong string "ABCDEFG", but you only want to look for
"ABCDEF", i.e. len=6.  The string_list happens to have an existing
string "ABCDEFG".  The insert-index function will report an exact
match, but that does not mean you found what you are looking for. 

For the particular case of "looking up e-mail from a string-list
used for the mailmap, using a string that potentially has an extra
'>' at the end", it may not be an issue (i.e. your overlong string
would be "ABCDEF>", and the string-list used for the mailmap will
not have an entry that ends with '>'), but it is likely that people
will try to mimic this function or try to generalize and move it to
strbuf.c and at that point, such a special case condition will no
longer hold and the bug will manifest itself.  Being defensive like
the above is a way to avoid that.