Re: [glibc PATCH] fcntl-linux.h: add F_OFD_*32 constants

[Mike Frysinger <vapier@gentoo.org>]

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On 18 Aug 2016 09:49, Jeff Layton wrote:
> On Thu, 2016-08-18 at 06:04 -0700, Mike Frysinger wrote:
> > On 18 Aug 2016 08:03, Jeff Layton wrote:
> > > --- a/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> > > +++ b/sysdeps/unix/sysv/linux/bits/fcntl-linux.h
> > > @@ -127,11 +127,20 @@
> > >     This means that they are inherited across fork or clone with CLONE_FILES
> > >     like BSD (flock) locks, and they are only released automatically when the
> > >     last reference to the the file description against which they were acquired
> > > -   is put. */
> > > +   is put.  */
> > >  #ifdef __USE_GNU
> > > > > -# define F_OFD_GETLK	36
> > > > > -# define F_OFD_SETLK	37
> > > > > -# define F_OFD_SETLKW	38
> > > +# if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
> > > > > +#  define F_OFD_GETLK		36
> > > > > +#  define F_OFD_SETLK		37
> > > > > +#  define F_OFD_SETLKW		38
> > > +# else
> > > > > +#  define F_OFD_GETLK32		39
> > > > > +#  define F_OFD_SETLK32		40
> > > > > +#  define F_OFD_SETLKW32	41
> > > > > +#  define F_OFD_GETLK		F_OFD_GETLK32
> > > > > +#  define F_OFD_SETLK		F_OFD_SETLK32
> > > > > +#  define F_OFD_SETLKW		F_OFD_SETLKW32
> > > +# endif
> > >  #endif
> > 
> > i think we should define *64 and *32 variants all the time, and
> > then route the F_OFD_GETLK/etc... to them based on compile mode.
> 
> Sorry, I don't quite understand here. The whole point is that the
> existing F_OFD_* constants are already implicitly 64-bit. Why do we
> need separate constants postfixed with "64" that no one will ever use?

you're making them not explicitly 64-bit when off_t!=off64_t.
all the other commands in this file have used the convention:
	<cmd>: automatically 32-bit or 64-bit
	<cmd>64: always 64-bit

so the header would do:
#define F_OFD_GETLK64 36
#define F_OFD_SETLK64 37
#define F_OFD_SETLKW64 38
#if __OFF_T_MATCHES_OFF64_T || defined __USE_FILE_OFFSET64
# define F_OFD_GETLK F_OFD_GETLK64
# define F_OFD_SETLK F_OFD_SETLK64
# define F_OFD_SETLKW F_OFD_SETLKW64
#else
# define F_OFD_GETLK 39
# define F_OFD_SETLK 40
# define F_OFD_SETLKW 41
#endif

the defines deviate a bit from the names used on the kernel side,
but we've already done that, and you're proposed patch does too.
-mike

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