Re: RTEMS Targets Issue #2 - ftello()/fseeko()

[Corinna Vinschen <vinschen at redhat dot com>]

On Mar 20 14:18, Yaakov Selkowitz wrote:
> On 2016-03-20 07:35, Corinna Vinschen wrote:
> >On Mar 19 22:35, Yaakov Selkowitz wrote:
> >>On 2016-03-19 12:10, Joel Sherrill wrote:
> >>>But now have:
> >>>
> >>>#if __LARGEFILE_VISIBLE
> >>>
> >>>Does the newlib guard need tinkering, the RTEMS default
> >>>features, or the test code in RTEMS?
> >>
> >>feature_test_macros(7) says that _XOPEN_SOURCE >= 500 includes these two
> >>largefile functions implicitly, but fseeko(3) says they are also
> >>POSIX.1-2001.  Does changing the guard to:
> >>
> >>#if __LARGEFILE_VISIBLE || __POSIX_VISIBLE >= 200112
> >>
> >>fix this issue?
> >
> >glibc's fseeko/ftello man page claims this guard:
> >
> >    _FILE_OFFSET_BITS == 64 || _POSIX_C_SOURCE >= 200112L ||
> >    _XOPEN_SOURCE >= 600
> >    (defining the obsolete _LARGEFILE_SOURCE macro also works)
> 
> The joys of conflicting documentation.  -D_XOPEN_SOURCE=600 will get you
> _POSIX_C_SOURCE=200112L automatically, but -D_XOPEN_SOURCE=500 already gets
> you __USE_LARGEFILE (as, per feature_test_macros(7), _LARGEFILE_SOURCE is
> "implicitly defined if _XOPEN_SOURCE is defined with a value greater than or
> equal to 500"), so 500 would be more accurate here.
> 
> In any case, I'll post a patch for fseeko/ftello shortly.
> 
> >Note especially the _FILE_OFFSET_BITS == 64.  So fseeko/ftello are
> >always defined on systems with sizeof(off_t) == 8.
> 
> This is the exception to the "-D_FILE_OFFSET_BITS=64 as no affect on 64-bit
> systems" rule; try compiling with -ansi and you should see they are not.
> Note that _POSIX_C_SOURCE=200809L is on by default, so maybe that's what
> you're seeing?

I'm not sure I understand.  I only referred to the man page, I didn't
test this.  Can you expand on this a bit?


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

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