Re: #if vs. #ifdef -- again (was: AC_CHECK_SIZEOF failing on undefined HAVE_STDINT_H with -Werror)

[Stepan Kasal]

Hello again,

On Tue, Aug 15, 2006 at 03:45:13PM +0200, Ralf Wildenhues wrote:
> http://cygwin.com/ml/autoconf-patches/2000-q1/msg00101.html

this mail gives the folowing impression:

1) In config.h, the macro should be either defined to 1 or left
undefined, so that both #if and #ifdef work in the code.

2) In the code, #if should be used, so that it works in the negative
case, no matter whether the macro is undefined or defined to 0.

The rationale probaly was that when someone is filling in the
config.h.in template manually, they could possibly define the macro
to 0.  (Or is it that a prehistoric version of autoconf did this?
If yes, it has to be more than 12 years, so we are not bounded by it.)

Anyway, there still is no reason agains switching to #ifdef, both in
the manual and in the code.

Have a nice day,
        Stepan