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@node va_arg
@section @code{va_arg}
@findex va_arg
POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/va_arg.html}
Gnulib module: ---
Portability problems fixed by Gnulib:
@itemize
@end itemize
Portability problems not fixed by Gnulib:
@itemize
@item
The second argument of @code{va_arg} must be a type that is invariant under
the ``default argument promotions'' (ISO C 99 6.5.2.2 paragraph 6). This
means that the following are not valid here:
@table @asis
@item @samp{float}
Use @samp{double} instead.
@item @samp{bool}
Use @samp{int} instead.
@item Integer types smaller than @samp{int}.
Use @samp{int} or @samp{unsigned int} instead.
@end table
This is a portability problem because you don't know the width of some
abstract types like @code{uid_t}, @code{gid_t}, @code{mode_t}. So, instead of
@smallexample
mode = va_arg (ap, mode_t);
@end smallexample
you have to write
@smallexample
mode = (sizeof (mode_t) < sizeof (int)
? va_arg (ap, int)
: va_arg (ap, mode_t));
@end smallexample
@end itemize
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