From: Johannes Sixt <j6t@kdbg.org>
Date: Wed, 17 May 2017 18:15:03 GMT
Subject: Re: [PATCH v1 2/5] Teach git to optionally utilize a file system monitor to speed up detecting new or changed files.
Message-ID: <2e5ea82d-3b8f-f508-e2af-5f193241a573@kdbg.org>
In-Reply-To: <0a3f38b7-788b-b364-3fef-83191e4b9bea@gmail.com>

Am 17.05.2017 um 16:26 schrieb Ben Peart:
> On 5/16/2017 3:13 PM, Johannes Sixt wrote:
>> Am 16.05.2017 um 19:17 schrieb Ben Peart:
>>> OK, now I'm confused as to the best path for adding a get_be64.  This
>>> one is trivial:
>>>
>>> #define get_be64(p)    ntohll(*(uint64_t *)(p))
>>
>> I cringe when I see a cast like this. Unless you can guarantee that p is
>> char* (bare or signed or unsigned), you fall pray to strict aliasing
>> violations, aka undefined behavior. And I'm not even mentioning correct
>> alignment, yet.
> 
> Note, this macro is only used where the CPU architecture is OK with 
> unaligned memory access.

I'm not worried about the unaligned memory access: It either works, or 
we get a SIGBUS. The undefined behavior is more worrisome because the 
code may work or not, and we can never be sure which it is.

-- Hannes