From: Nguyen Thai Ngoc Duy <pclouds@gmail.com>
Date: Tue, 26 Apr 2011 15:32:31 GMT
Subject: Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time
Message-ID: <BANLkTi=ECjmjBLfS=s6fMWXgtxDYmxcP5g@mail.gmail.com>
In-Reply-To: <7v7hahghls.fsf@alter.siamese.dyndns.org>

2011/4/26 Junio C Hamano <gitster@pobox.com>:
> Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes:
>
>> strbuf_grow(sb, 0) may allocate less than requested len and violate the
>> next assertion.
>>
>> Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
>> ---
>>  strbuf.h |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/strbuf.h b/strbuf.h
>> index 07060ce..ab213da 100644
>> --- a/strbuf.h
>> +++ b/strbuf.h
>> @@ -34,7 +34,7 @@ extern void strbuf_grow(struct strbuf *, size_t);
>>
>>  static inline void strbuf_setlen(struct strbuf *sb, size_t len) {
>>       if (!sb->alloc)
>> -             strbuf_grow(sb, 0);
>> +             strbuf_grow(sb, len);
>>       assert(len < sb->alloc);
>
> This looks so obviously correct that it is scary.
>
> How could 60 callsites of this function manage to have run without crashes
> so far?  They all happen to use the function on a buffer that already has
> something on it?

I guess no current call site does _setlen right after initialization.
It's new code that triggers it.
-- 
Duy