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

[Yaakov Selkowitz <yselkowitz at cygwin dot com>]

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?

--
Yaakov