Re: va_list function portability doco

[Kevin Ryde]

Akim Demaille <address@hidden> writes:
>
> It seems like this guy never went in.  Would you install it please?

I'd like to propose a newer version below.

        * doc/autoconf.texi (Function Portability): Notes on va_copy, va_list.


@item @code{va_copy}
@c @fuindex va_copy
@prindex @code{va_copy}
The ISO C99 standard provides @code{va_copy} for copying
@code{va_list} variables.  It may be available in older environments
too, though possibly as @code{__va_copy} (eg. @command{gcc} in strict
C89 mode).  These can be tested with @code{#ifdef}.  A fallback to
@code{memcpy (&dst, &src, sizeof(va_list))} will give maximum
portability.

@item @code{va_list}
@c @fuindex va_list
@prindex @code{va_list}
@code{va_list} is not necessarily just a pointer.  It can be a
@code{struct} (eg. @command{gcc} on Alpha), which means @code{NULL} is
not portable.  Or it can be an array (eg. @command{gcc} in some
PowerPC configurations), which means as a function parameter it can be
effectively call-by-reference and library routines might modify the
value back in the caller (eg. @code{vsnprintf} in the GNU C Library
2.1).