Re: AC_CYGWIN

[Assar Westerlund]

Patrick Welche <address@hidden> writes:
> I found the definition of AC_CYGWIN in lib/autoconf/specific.m4:
> 
> # AC_CYGWIN
> # ---------
> # Check for Cygwin.  This is a way to set the right value for  
> # EXEEXT.

You will notice that this does not set EXEEXT.

> AU_DEFUN([AC_CYGWIN],
> [AC_CANONICAL_HOST
> AC_DIAGNOSE([obsolete],
>         [$0 is obsolete: use AC_CANONICAL_HOST and $host_os])dnl
> case $host_os in  
>   *cygwin* ) CYGWIN=yes;;
>      * ) CYGWIN=no;;
> esac
> ])# AC_CYGWIN
> 
> 
> Several things I don't understand: google brought up an email which
> esentially said "Don't use AC_REQUIRE inside AU_DEFUN", but then how
> do you say "Only run AC_CANONICAL_HOST if it hasn't been run before".

I think the point is that you shall not AC_REQUIRE inside an AU_DEFUN,
but you can AC_REQUIRE inside an AC_DEFUN.

Remember that an AU_DEFUN is expanded by autoupdate, so it should
really only contain the old macro written in terms of the new one.

> Also, AU_DEFUN (OLD-MACRO, IMPLEMENTATION, [MESSAGE]), so why use
> AC_DIAGNOSE instead of [MESSAGE]?

It seems that AC_CYGWIN has not been updated to take advantage of
3-argument AU_DEFUN.

Hope this helps.