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Date: Sun, 14 Mar 2004 20:03:24 +1100
From: Tim Robbins <tjr@freebsd.org>
To: Daniel Eischen <eischen@vigrid.com>
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cc: threads@freebsd.org
Subject: Re: RFC: getc() and putc() as macros
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On Sun, Mar 14, 2004 at 12:53:55AM -0500, Daniel Eischen wrote:

> On Sun, 14 Mar 2004, Tim Robbins wrote:
> 
> > On Sat, Mar 13, 2004 at 10:05:14AM -0500, Daniel Eischen wrote:
> > 
> > > On Sat, 13 Mar 2004, Tim Robbins wrote:
> > > 
> > > > The patch below re-adds macro versions of getc(), getchar(), putc(),
> > > > putchar(), feof(), ferror(), fileno() and clearerr(), using the value of
> > > > __isthreaded to decide between the fast inline single-threaded code and
> > > > the more general function equivalent (as suggested by Alfred). Is this
> > > > approach safe?
> > > 
> > > I don't really like this.  It exposes __isthreaded and others
> > > that are implementation.
> > 
> > Can you think of a better way?
> 
> I think it was I that got rid of the macros for getc() et al.
> I did it when libc_r was divorced from libc, and the macro
> _THREAD_SAFE was no longer necessary.
> 
> Solaris uses _REENTRANT to toggle between macros and functions.
> For the macro versions, it accesses the FILE directly instead
> of making a function call.
> 
> I think the _unlocked versions of the functions are there for
> a reason.  If an application isn't going to be threaded, then
> it can always use the unlocked versions...

Perhaps they could in theory, but in practice, single threaded applications
don't use the _unlocked functions. They haven't needed to, since most
serious operating systems except FreeBSD 5 provide getc() and putc() macros.

(I wish we put as much effort into optimizing stdio as we have put into
implementing a micro-optimized thread system like SA...)


Tim