Re: [PATCH] string-list: make compare function compatible with qsort(3)

From: Jeff King <peff@peff.net>
Date: Dec 21, 2016, 16:12 UTC
Message-ID: <20161221161220.x3qkcwmuangcdc2l@sigill.intra.peff.net>
In-Reply-To: <c7bac0b7-c555-162f-7880-0355831cee48@web.de>

On Wed, Dec 21, 2016 at 10:36:41AM +0100, René Scharfe wrote:

> One shortcoming is that the comparison function is restricted to working
> with the string members of items; util is inaccessible to it.  Another
> one is that the value of cmp is passed in a global variable to
> cmp_items(), making string_list_sort() non-reentrant.

I think this approach is OK for string_list, but it doesn't help the general case that wants qsort_s() to actually access global data. I don't know how common that is in our codebase, though.

So I'm fine with it, but I think we might eventually need to revisit the qsort_s() thing anyway.

Show 5 quoted lines

> Remove the intermediate layer, i.e. cmp_items(), make the comparison
> functions compatible with qsort(3) and pass them pointers to full items.
> This allows comparisons to also take the util member into account, and
> avoids the need to pass the real comparison function to an intermediate
> function, removing the need for a global function.

I'm not sure if access to the util field is really of any value, after looking at it in:

  http://public-inbox.org/git/20161125171546.fa3zpapbjngjcl26@sigill.intra.peff.net/

Though note that if we do take this patch, there are probably one or two spots that could switch from QSORT() to string_list_sort().

-Peff