cvs commit: src/include stdio.h src/lib/libc/sys lseek.2 pathconf.2 src/sys/kern vfs_syscalls.c src/sys/sys filio.h unistd.h

Andrey Chernov ache at
Fri Apr 6 17:33:33 UTC 2007

On Fri, Apr 06, 2007 at 06:27:11PM +0200, Pawel Jakub Dawidek wrote:
> > Feel free to invent any other __*_VISIBLE tag to exclude this addition 
> > from namespace for programs which may define their own SEEK_DATA etc 
> > which is allowed f.e. in POSIX namespace. Look like other __*_VISIBLE tags 
> > are implemented and what they does. Default is turn all on.
> Ok, can someone help me with this?

The very basics are: application request particular namespace at compile 
time using -D_*_SOURCE define. According to choosed _*_SOURCE some of 
__*_VISIBLE macros are defined and some not (if no namespace choosed, all 
__*_VISIBLE are defined, default case). According to __*_VISIBLE macros 
defined some functions or definitions becomes hidden or visible.

See the very end of /sys/sys/cdefs.h for live examples.

__*_VISIBLE macros are in form __<standard or platform>_VISIBLE
For example can be __CDDL_VISIBLE or __ZFS_VISIBLE (depends on exactly 
where those extensions was introduced). Lets take __ZFS_VISIBLE for the 
rest of explanation.

You need to directly hide those extensions for every particular 
_*_SOURCE namespace, i.e. add 
#define __ZFS_VISIBLE 0
to all of them and enable extensions 
#define __ZFS_VISIBLE 1
only for the last (default) case (at the very end of /sys/sys/cdefs.h)

Then use (for unistd.h)
#define SEEK_DATA ...

Try to asking more help at standards@ or bde@ who notice it first and 
knows this thing apparenly better than me.

> > In any case adding them to stdio.h is premature action - I not see yet
> > corresponding fseek() code.
> I'm looking at removing it from stdio.h.


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