Re: [PATCH v9 09/14] pkt-line: add packet_write_gently()

From: Lars Schneider <larsxschneider@gmail.com>
Date: Oct 5, 2016, 19:06 UTC
Message-ID: <B1968DDD-7EAA-477B-B088-5F2A83F29C8C@gmail.com>
In-Reply-To: <xmqqd1jfucwo.fsf@gitster.mtv.corp.google.com>

Show 20 quoted lines

> On 04 Oct 2016, at 21:33, Junio C Hamano <gitster@pobox.com> wrote:
> 
> larsxschneider@gmail.com writes:
> 
>> From: Lars Schneider <larsxschneider@gmail.com>
>> 
>> 
>> +static int packet_write_gently(const int fd_out, const char *buf, size_t size)
>> +{
>> +	static char packet_write_buffer[LARGE_PACKET_MAX];
>> +	const size_t packet_size = size + 4;
>> +
>> +	if (packet_size > sizeof(packet_write_buffer))
>> +		return error("packet write failed - data exceeds max packet size");
> 
> Hmph, in the previous round, this used to be "is the size larger
> than sizeof(..) - 4?", which avoided integer overflow issue rather
> nicely and more idiomatic.  If size is near the size_t's max,
> packet_size may wrap around to become very small, and we won't hit
> this error, will we?

You are right. Would the solution below be acceptable? I would like to keep the `packet_size` variable as it eases the rest of the function.

 
 	const size_t packet_size = size + 4;
 
-	if (packet_size > sizeof(packet_write_buffer))
+	if (size > sizeof(packet_write_buffer) - 4)
 		return error("packet write failed - data exceeds max packet size");

Thanks, Lars