Re: [Boost-testing] [vacpp][iostreams] Help fixing stream_offset_64bit_test

From: Christopher Cambly (ccambly_at_[hidden])
Date: 2008-01-15 22:24:27

> Christopher Cambly/Toronto/IBM_at_IBMCA wrote:
> > >
> > >>>> While we're on the subject of compiler flags for large file
support,
> > >>>> there's another part of the Iostreams library that I have
attempted
> to
> > >>>> configure for IBM. I've read the documentation, but it would be
> great
> >
> > > I guess if I was to tentatively suggest something for AIX in general
it
> > > would be _LARGE_FILE_API
> >
> > I didn't run into that one.
> >
>
> Forget I mentioned it :-) I spoke with the AIX developers today and they
> said applications shouldn't ever use _LARGE_FILE_API directly themselves;
> the macro just dictates whether the various *64 file API's and types are
> visible or not. But that macro has other dependencies as well.
>
>
> Here is the response from them to your original query:
> ****
> So, as for what the Boost code should use, note that the presence of
> _LARGE_FILES controls whether or not the file handling API's map to their
> counterparts -- in other words, it serves the same purpose that the coded
> conditional does below. (meaning the coded conditional in your code)
>
> In other words, if they simply always did this for AIX:
>       #  define BOOST_IOSTREAMS_FD_SEEK      lseek
>
> After including the standard header files, that's all taken care of
because
> if he has defined _LARGE_FILES, then lseek is already defined to lseek64.
> If _LARGE_FILES is not defined, then lseek is just lseek.   Also
> _LARGE_FILES defines off_t to be a long long instead of a long, so if you
> always just use the names "off_t" and "lseek"  (and so on), the types
will
> be correct for either defining or not defining _LARGE_FILES.
>
> The best info on this is in the AIX pubs, in the "Writing Programs That
> Access Large Files" page.
>
> ***
>
> I'm not sure whether or not this is a satisfactory response to your
> question.  The recommendation being that on AIX let the system headers
> determine the function to be called.  But...If I read the above
correctly,
> it also seems like if you really want to do it in the Boost, the code as
> you have it now in SVN  should work.
>

Sorry, the last statement is not entirely correct.  The code in SVN is:
# if defined(_LARGEFILE64_SOURCE) && \
      (!defined(_FILE_OFFSET_BITS) || _FILE_OFFSET_BITS != 64) || \
     defined(__IBMCPP__) && !defined(_LARGE_FILES) || \
     defined(BOOST_IOSTREAMS_HAS_LARGE_FILE_EXTENSIONS)

This code implies that __IBMCPP__ is the only compiler available on AIX.
gcc is available on AIX, and conversely XLC(__IBMCPP__) is available on
Linux.   The macro is (_AIX) for AIX. Maybe defined(_AIX) &&
!defined(_LARGE_FILES) would be better.  Just a thought.

Chris Cambly
XL C/C++ Compiler Development