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Message-ID: <20180501210553.GV1392@brightrain.aerifal.cx>
Date: Tue, 1 May 2018 17:05:53 -0400
From: Rich Felker <dalias@...c.org>
To: Patrick Oppenlander <patrick.oppenlander@...il.com>
Cc: musl@...ts.openwall.com
Subject: Re: Some questions
On Tue, May 01, 2018 at 10:10:45AM +1000, Patrick Oppenlander wrote:
> On Mon, Apr 30, 2018 at 1:16 PM, Rich Felker <dalias@...c.org> wrote:
> > On Mon, Apr 30, 2018 at 12:52:06PM +1000, Patrick Oppenlander wrote:
> >> - sigisemptyset uses bss. Could be implemented in a similar fashion to
> >> sigemptyset, save bss & would probably be faster.
> >
> > Ahh, yes. I wonder if gcc has any way to force const zero objects into
> > rodata rather than bss..? In any case memcmp is not an efficient way
> > to implement this, so maybe it should be changed.
>
> Doing this:
>
> diff --git a/src/signal/sigisemptyset.c b/src/signal/sigisemptyset.c
> index 312c66cf..28f74203 100644
> --- a/src/signal/sigisemptyset.c
> +++ b/src/signal/sigisemptyset.c
> @@ -4,6 +4,6 @@
>
> int sigisemptyset(const sigset_t *set)
> {
> - static const unsigned long zeroset[_NSIG/8/sizeof(long)];
> + static const unsigned long zeroset[_NSIG/8/sizeof(long)] = {};
> return !memcmp(set, &zeroset, _NSIG/8);
> }
>
> Makes it go into rodata.
>
> I agree that it should probably be rewritten to not use memcmp.
I'm just changing it to avoid memcmp. This gets rid of the bss and
makes the code smaller.
Rich
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