Re: [PATCH v4 05/12] sequencer.c: recognize "(cherry picked from ..." as part of s-o-b footer

Brandon Casey [off-list ref] writes:

On 2/12/2013 11:36 AM, Junio C Hamano wrote:

quoted

Brandon Casey [off-list ref] writes:

quoted

quoted

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+	return len > strlen(cherry_picked_prefix) + 1 &&
+		!prefixcmp(buf, cherry_picked_prefix) && buf[len - 1] == ')';
+}

Does the first "is it longer than the prefix?" check matter?  If it
is not, prefixcmp() would not match anyway, no?

Probably not in practice, but technically we should only be accessing
len characters in buf even though buf may be longer than len.  So the
check is just making sure the function doesn't access chars it's not
supposed to.

Sorry, I do not follow.  Isn't caller's buf terminated with LF at buf[len],
which would never match cherry_picked_prefix even if len is shorter
than the prefix?

Heh, I almost pointed that out in my reply.  Yes, buf will be terminated
with LF at buf[len].  And yes, that means that we will never get a false
positive from prefixcmp even if the comparison overruns buf+len while
doing its comparison.  That's why the check doesn't matter in practice,
i.e. based on the way that is_cherry_picked_from_line is being called
right now and the content of cherry_picked_prefix.

But, hasn't is_cherry_picked_from_line entered into a contract with the
caller and said "I will not access more than len characters"?

It's ok with me if you think it reads better without the check.

As Jonathan says, if you rewrite it to

	return buf[len - 1] == ')' && !prefixcmp(buf, cherry_picked_prefix);

then the code can keep its promise without the length check, because
it knows there is no ')' in cherry-picked-prefix, and it also knows
prefixcmp() stops at the first difference.

It is not a huge deal; I was primarily reacting to the ugly multi-line
boolean expresion that is not inside a pair of parentheses (and because
this is a "return" statement, there is no good reason to have parentheses
except that this is a multi-line expression), which looked odd.