Re: [PATCH 1/2] add MOVE_ARRAY

From: Jeff King <peff@peff.net>
Date: Jul 16, 2017, 10:31 UTC
Message-ID: <20170716103132.z36audbi7wxot7e6@sigill.intra.peff.net>
In-Reply-To: <ec78a849-36e4-4b1d-1ad6-46dcc39a1396@web.de>

On Sat, Jul 15, 2017 at 09:36:20PM +0200, René Scharfe wrote:

Show 8 quoted lines

> Similar to COPY_ARRAY (introduced in 60566cbb58), add a safe and
> convenient helper for moving potentially overlapping ranges of array
> entries.  It infers the element size, multiplies automatically and
> safely to get the size in bytes, does a basic type safety check by
> comparing element sizes and unlike memmove(3) it supports NULL
> pointers iff 0 elements are to be moved.
> 
> Also add a semantic patch to demonstrate the helper's intended usage.

If we have COPY_ARRAY(), I think it's foolish not to provide the matching MOVE_ARRAY(). If it were just the "if (n)", I might say we could just do this inline in the few calls that care. But I really like the size safety.

I agree with your comments elsewhere that we don't need to worry about the case where one of the arrays is NULL but the size is not zero. That's a flat-out bug.

-Peff