From: Junio C Hamano <gitster@pobox.com>
Date: Tue, 26 Apr 2011 15:25:19 GMT
Subject: Re: [PATCH] strbuf: allocate enough space when strbuf_setlen() is called first time
Message-ID: <7v7hahghls.fsf@alter.siamese.dyndns.org>
In-Reply-To: <1303820660-744-1-git-send-email-pclouds@gmail.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?

Well spotted, thanks.