Re: [PATCH]: Thread safe stdio with cygwin

[Jeff Johnston <jjohnstn at redhat dot com>]

I should have added that there is no reason not to check in your patch 
which I have just done.
I can add the initialization/closing in __sbprintf().

-- Jeff J.

Jeff Johnston wrote:

> Thomas Pfaff wrote:
>
> > Jeff,
> >
> > memset makes only sure that _lock does not contain random data before 
> > __lock_init_recursive. __lock_init_recursive is called later when the 
> > file is really opened.
>
>
> I assumed you were worried about something accessing the file pointer 
> before fopen/freopen returned the file pointer so it would then make 
> sense just to initialize it earlier.  Otherwise, the 
> __lock_init_recursive should initialize the lock without need for 
> pre-initialization.
>
> > __sbprintf is a special case because it generates a fake FILE pointer 
> > and its associated buf on the stack, therefore there is no need to 
> > lock it fo thread safety.
>
>
> There may be no need to lock, but the VFPRINTF code attempts a lock 
> and unlock anyway.  It then makes sense to ensure that the lock is 
> validly initialized/closed for any platform's lock implementation.
> -- Jeff J.
>
> > Thomas
> >
> > Jeff Johnston wrote:
> >
> > > Thomas,
> > >
> > >  You should be using __lock_init_recursive to initialize the locks 
> > > rather than zeroing them out.
> > > The code in __sbprintf should probably be closing the lock after the 
> > > call to VFPRINTF as well.
> > >
> > > -- Jeff J.
> > >
> > > Thomas Pfaff wrote:
> > >
> > > > This patch adds support for thread safe stdio for Cygwin.
> > > >
> > > > Cygwin uses dynamic mutexes for locking, therefore it is
> > > > necessary to:
> > > >
> > > > 1. Initialize FILE pointers _lock properly.
> > > > 2. Destroy the lock when it is no longer needed.
> > > >
> > > > Regards,
> > > >
> > > > Thomas
> > > >
> > > > 2004-01-12  Thomas Pfaff  <tpfaff@gmx.net>
> > > >
> > > >     * libc/stdio/fclose.c: Include sys/lock.h.
> > > >     (fclose): Destroy lock when file is closed.
> > > >     * libc/stdio/findfp.c (__sfp): Initialize file pointers _lock
> > > >     member.
> > > >     * libc/stdio/freopen.c: Include sys/lock.h.
> > > >     (_freopen_r): Destroy lock when file is closed.
> > > >     * libc/stdio/vfprintf.c (__sbprintf): Initialize file pointers
> > > >     _lock member.
> > > >
> > > >