From: Johannes Schindelin <johannes.schindelin@gmx.de>
Date: Wed, 28 Dec 2005 20:38:32 GMT
Subject: Re: [PATCH] Avoid allocating 0 bytes, was Re: [PATCH 4/4] git-compat-util.h: dietlibc-friendly x{malloc,realloc,calloc}
Message-ID: <Pine.LNX.4.63.0512282134380.2236@wbgn013.biozentrum.uni-wuerzburg.de>
In-Reply-To: <Pine.LNX.4.63.0512262134290.19331@wbgn013.biozentrum.uni-wuerzburg.de>

Hi,

On Mon, 26 Dec 2005, Johannes Schindelin wrote:

> On Mon, 26 Dec 2005, Junio C Hamano wrote:
> 
> > Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:
> > 
> > > diff --git a/csum-file.c b/csum-file.c
> > > index 5f9249a..2c0f097 100644
> > > --- a/csum-file.c
> > > +++ b/csum-file.c
> > > @@ -121,6 +121,9 @@ int sha1write_compressed(struct sha1file
> > >  	unsigned long maxsize;
> > >  	void *out;
> > >  
> > > +	if (size == 0)
> > > +		return 0;
> > > +
> > >  	memset(&stream, 0, sizeof(stream));
> > >  	deflateInit(&stream, Z_DEFAULT_COMPRESSION);
> > >  	maxsize = deflateBound(&stream, size);
> > 
> > I think this and the one in sha1_file.c::write_sha1_file() are
> > wrong; 0-size input would not result in 0-size output.  Have you
> > tested them by actually exercising the codepaths you touched?
> 
> No, I did not test them.

Now I did. To make a long story short: this patch is wrong, wrong, wrong. 
Further, I think it is safe to assume that deflateBound() returns > 0.

Ciao,
Dscho