Re: [PATCH 3/8] longest_ancestor_length(): use string_list_split()

[Michael Haggerty <mhagger@alum.mit.edu>]

On 09/28/2012 12:48 AM, Junio C Hamano wrote:
> Michael Haggerty <mhagger@alum.mit.edu> writes:
> 
>> -	for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
>> -		for (colon = ceil; *colon && *colon != PATH_SEP; colon++);
>> -		len = colon - ceil;
>> +	string_list_split(&prefixes, prefix_list, PATH_SEP, -1);
>> +
>> +	for (i = 0; i < prefixes.nr; i++) {
>> +		const char *ceil = prefixes.items[i].string;
>> +		int len = strlen(ceil);
>> +
> 
> Much nicer than the yucky original ;-)

If your winky-smiley implies irony, then I would like to object.  Even
though the original is not difficult to understand, it is more difficult
to review than the new version because one has to think about off-by-one
errors etc.  The new version has a bit more boilerplate, but a quick
read suffices both to understand it and to see that it is correct.
Though of course I admit that the improvement is small.

But the main point of this change is to move towards using more testable
parts, so it is a step forward regardless of whether it is more readable.

>>  		if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
>>  			continue;
>> -		strlcpy(buf, ceil, len+1);
>> +		memcpy(buf, ceil, len+1);
>>  		if (normalize_path_copy(buf, buf) < 0)
>>  			continue;
> 
> Why do you need this memcpy in the first place?  Isn't ceil already
> a NUL terminated string unlike the original code that points into a
> part of the prefix_list string?  IOW, why not
> 
> 	normalize_path_copy(buf, ceil);
> 
> or something?

Good point.  I will fix this in v2.

> Can normalize_path_copy() overflow buf[PATH_MAX+1] here (before or
> after this patch)?

normalize_path_copy() can only shrink paths, not grow them.  So the
length check on ceil guarantees that the result of normalize_path_copy()
will fit in buf.

Michael

-- 
Michael Haggerty
mhagger@alum.mit.edu
http://softwareswirl.blogspot.com/