From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jim Meyering <jim@meyering.net>
Subject: Re: [PATCH] diff: avoid stack-buffer-read-overrun for very long name
Date: Thu, 26 Apr 2012 18:22:11 +0200
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Cc: Marcus Karlsson <mk@acc.umu.se>, git list <git@vger.kernel.org>
To: Junio C Hamano <gitster@pobox.com>
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Junio C Hamano wrote:
> Jim Meyering <jim@meyering.net> writes:
>
>> What do you think about replacing those two append-if-needed two-liners:
>>
>>     if (buffer2.len && buffer2.buf[buffer2.len - 1] != '/')
>>             strbuf_addch(&buffer2, '/');
>>
>> by something that readably encapsulates the idiom:
>>
>>     strbuf_append_if_absent (&buffer2, '/');
>>
>> (though the name isn't particularly apt, because you might
>> take "absent" to mean "not anywhere in the string," so maybe
>>   strbuf_append_if_not_already_at_end (ugly) or
>>   strbuf_append_uniq
>> )
>
> I am not good at names, but strbuf_terminate_with(&buffer2, '/')
> perhaps?

Maybe, but it still doesn't evoke the conditional nature
of don't-append-if-already-there the operation.  i.e., one
might wonder how it's different from "strbuf_append".

How about one of these?

  strbuf_ensure_suffix  // but might make you think suffix==more than 1 byte
  strbuf_ensure_last_byte    // maybe?
  strbuf_ensure_last_byte_is // rather long, but apt

>> There are several other uses that would benefit from such a transformation:
>> To find the easy ones, I ran this:
>>
>>   git grep -B1 "strbuf_addch.*'"|grep -A1 '!='
>>
>> I've manually marked/separated the ones that don't apply.
>>
>> Note how only 2 of the 6 candidates ensure that length is positive
>> before using ".len - 1":
>
> Yikes, that is embarrasing ;-)

Knowing you/git, each is because the buffer is known to be non-empty.