Re: "The `-a', `-o', `(', and `)' operands are not portable": please clarify

[Paolo Bonzini]

On 08/12/2009 02:37 AM, Reuben Thomas wrote:
> 2009/8/7 Paolo Bonzini<address@hidden>:
> > AS_INIT ensures that you can define shell functions normally using
> >
> >   foo () {
> >     # body
> >   }
> >
> > Alternatively, there is AS_REQUIRE_SHELL_FN that provides a way to define
> > shell functions from within a m4 macro,
>
> So when should one use AS_INIT, and when should one prefer AS_REQUIRE _SHELL_FN?

It's different things.

AS_INIT initializes m4sh, including ensuring that the current shell 
supports functions.  After that you can define shell functions with the 
normal syntax.

If you write a m4sh script, you can then define shell functions normally 
using shell syntax.  Even if write a library like Autotest, shell 
functions that are always needed can be defined normally using shell syntax.

AS_REQUIRE_SHELL_FN is a separate thing.  It provides a convenience for 
defining a shell function, and will expand the function definition just 
once.  Also, the function definition will be placed early in the file, 
just after the initialization code.

AS_REQUIRE_SHELL_FN is useful if you do not know in advance which 
functions will be needed, or what code they will expand to.

For example, AC_CHECK_FUNC does two things: 1) it uses 
AS_REQUIRE_SHELL_FN to generate a shell function with the test code, and 
2) it produces a call to the function.  The call ends up where 
AC_CHECK_FUNC was in the configure.ac file, while the shell function is 
placed early in the configure script.

AC_CHECK_FUNC uses AS_REQUIRE_SHELL_FN because Autoconf scripts may not 
all need the check-function test code, and because the body of the 
function is not known, say, when AC_INIT is executed (because it depends 
on the language being tested).

Paolo