Re: [PATCH] Avoid allocating 0 bytes, was Re: [PATCH 4/4] git-compat-util.h: dietlibc-friendly x{malloc,realloc,calloc}

Hi,

On Mon, 26 Dec 2005, Johannes Schindelin wrote:

On Mon, 26 Dec 2005, Junio C Hamano wrote:

quoted

Johannes Schindelin [off-list ref] writes:

quoted

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