Re: shell or M4sugar?

[Julien ÉLIE]

Hi Zack,

> > AS_CASE([$host],
> >       [*-openbsd*],
> >           [CC_WARNINGS=`echo "$CC_WARNINGS" | sed 's/-Wredundant-decls //'`])
>
> Using AS_CASE means you don't have to write unbalanced parentheses in
> your configure.ac or extension .m4 file.  If this is the top level of
> configure.ac, it also means the AC_REQUIRE machinery knows not to emit
> required macros inside the conditional.

Noted, thanks for your detailed answer.


> Using AS_ECHO means you don't have to worry about echo interpreting
> text to be echoed as options.  Sometimes you know that's not relevant,
> but in this example, $CC_WARNINGS is a list of compiler options, so I
> would definitely use AS_ECHO.
>
> AS_ECHO(["$CC_WARNINGS"]) - yes, you need to quote for *both* m4 and 
> shell - but otherwise yes, that's the preferred form.
OK.

Incidentally, the below sentence present in the Section of the 
documentation for the echo built-in shell function could be worthwhile 
also writing in the AS_ECHO documentation.  It would make clearer what 
AS_ECHO does.

"M4sh provides AS_ECHO and AS_ECHO_N macros which choose between various 
portable implementations: ‘echo’ or ‘print’ where they work, printf if 
it is available, or else other creative tricks in order to work around 
the above problems."


> > Or the CC_WARNINGS be m4_define'd and then manipulated through m4_append
> > & like, and use m4_bpatsubst for doing what sed does?
>
> That won't work here; the value of $host is not yet known when you run
> autoconf, only when you run configure.
>
> (This is the difference between the "m4sugar" and "m4sh" layers.  m4_*
> macros are fully executed at autoconf time, AS_* macros generate code
> that will be executed at configure time.)

I'll remember that, thanks.

--
Julien ÉLIE

« J'aime les calculs faux car ils donnent des résultats plus justes. »
  (Jean Arp)