Re: new module 'fseeko'

[Bruno Haible]

Eric Blake wrote:
> > Btw, what is AC_FUNC_FSEEKO good for?
> 
> AC_FUNC_FSEEKO turns on large file support, if necessary.

Actually, it doesn't. Paul explained it: AC_FUNC_FSEEKO makes the fseeko()
and ftello() declarations visible (and all the *64 struct and function
declarations) but does *not* do what AC_SYS_LARGEFILE does.

> > 2007-04-25  Bruno Haible  <address@hidden>
> > 
> >     * modules/fseeko: New file.
> ...
> > + #if @GNULIB_FSEEKO@
> > + # if address@hidden@
> > + /* Assume 'off_t' is the same type as 'long'.  */
> > + #  define fseeko fseek
> > + # endif
> 
> Is that assumption safe, or should we also find the size of long and off_t
> to verify that situation?

Verifying it cannot hurt. I commit the appended patch. Thanks for the
suggestion.

> > + #else
> > + # undef fseeko
> > + # define fseeko(f,o,w) \
> > +    (GL_LINK_WARNING ("fseeko is unportable - " \
> > +                      "use gnulib module fseeko for portability"), \
> > +     fseeko (f, o, w))
> > + #endif
> 
> Should we also add a link warning for programs that use fseek/ftell
> instead of fseeko/ftello, telling the user they are potentially
> artificially limited by not using off_t?

Good idea! Can you do this?

Bruno

2007-04-26  Bruno Haible  <address@hidden>

        * lib/stdio_.h (fseeko, ftello): Check that off_t has the same size as
        'long' when we assume it.
        Suggested by Eric Blake.

*** lib/stdio_.h        25 Apr 2007 09:14:49 -0000      1.20
--- lib/stdio_.h        26 Apr 2007 09:36:47 -0000
***************
*** 38,44 ****
  #include <stdarg.h>
  #include <stddef.h>
  
! #if @GNULIB_FFLUSH@ && @REPLACE_FFLUSH@
  /* Get off_t.  */
  # include <sys/types.h>
  #endif
--- 38,44 ----
  #include <stdarg.h>
  #include <stddef.h>
  
! #if (@GNULIB_FFLUSH@ && @REPLACE_FFLUSH@) || (@GNULIB_FSEEKO@ && 
address@hidden@) || (@GNULIB_FTELLO@ && address@hidden@)
  /* Get off_t.  */
  # include <sys/types.h>
  #endif
***************
*** 220,225 ****
--- 220,226 ----
  #elif @GNULIB_FSEEKO@
  # if address@hidden@
  /* Assume 'off_t' is the same type as 'long'.  */
+ typedef int verify_fseeko_types[2 * (sizeof (off_t) == sizeof (long)) - 1];
  #  define fseeko fseek
  # endif
  #else
***************
*** 233,238 ****
--- 234,240 ----
  #if @GNULIB_FTELLO@
  # if address@hidden@
  /* Assume 'off_t' is the same type as 'long'.  */
+ typedef int verify_ftello_types[2 * (sizeof (off_t) == sizeof (long)) - 1];
  #  define ftello ftell
  # endif
  #else