linux-kernel - Re: [PATCH 3/4] tools/nolibc: move FD

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Message-ID: <d8d9ab91-0617-468e-a82d-9f271c5e6a7f@t-8ch.de>
Date: Sun, 29 Jun 2025 10:53:34 +0200
From: Thomas Weißschuh <linux@...ssschuh.net>
To: Willy Tarreau <w@....eu>
Cc: Thomas Weißschuh <thomas.weissschuh@...utronix.de>, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/4] tools/nolibc: move FD_* definitions to sys/select.h

On 2025-06-29 10:46:28+0200, Willy Tarreau wrote:
> On Mon, Jun 23, 2025 at 04:56:18AM +0200, Willy Tarreau wrote:
> > On Sun, Jun 22, 2025 at 09:58:52PM +0200, Thomas Weißschuh wrote:
> > > On 2025-06-22 09:19:58+0200, Willy Tarreau wrote:
> > > > Hi Thomas,
> > > > 
> > > > On Sat, Jun 21, 2025 at 10:21:47AM +0200, Thomas Weißschuh wrote:
> > > > > On 2025-06-20 12:02:50+0200, Willy Tarreau wrote:
> > > > > > Modern programs tend to include sys/select.h to get FD_SET() and
> > > > > > FD_CLR() definitions as well as struct fd_set, but in our case it
> > > > > > didn't exist. Let's move these definitions from types.h to sys/select.h
> > > > > > to help port existing programs.
> > > > > > 
> > > > > > Signed-off-by: Willy Tarreau <w@....eu>
> > > > > 
> > > > > <snip>
> > > > > 
> > > > > > diff --git a/tools/include/nolibc/types.h b/tools/include/nolibc/types.h
> > > > > > index 16c6e9ec9451f..0b51ede4e0a9c 100644
> > > > > > --- a/tools/include/nolibc/types.h
> > > > > > +++ b/tools/include/nolibc/types.h
> > > > > > @@ -10,6 +10,7 @@
> > > > > >  #ifndef _NOLIBC_TYPES_H
> > > > > >  #define _NOLIBC_TYPES_H
> > > > > >  
> > > > > > +#include "sys/select.h"
> > > > > 
> > > > > Is this really necessary?
> > > > 
> > > > Not sure what you mean. Do you mean that you would have preferred it
> > > > to be included from nolibc.h instead (which I'm equally fine with) or
> > > > that you'd prefer to have an empty sys/select.h ?
> > > 
> > > The former.
> > 
> > OK thanks, you're right, that's more consistent with the rest,
> > I'll do that and push it.
> 
> Trying it has reopened the circular dependencies can of worms :-(
> It's the same problem as usual that we've worked around till now
> by placing some types in types.h, except that this time fd_set is
> defined based on the macros FD_* that I moved to sys/select.h.

Can't fd_set also move to sys/select.h? This is how I read fd_set(3).
Even if it is not standards compliant, for nolibc it won't matter as in
the end everything is available anyaways.

> I'm giving up on this one for now as I don't want us to revisit
> that painful dependencies sequence. In theory it should be as simple
> as guarding types and function definitions independently, but in
> reality it's never as rocket science as it can also pop up in macros
> and rare typedefs.

Also the headers are always included in the order written down in
nolibc.h, so sys/select could be above types.h there.

> Instead I'll just provide a stub for sys/select.h just like for
> inttypes so that user code compiles without changing existing files.

That works for me, too.