Re: [PATCH] Add AC_REQUIRE_SHELL_FN

[Paolo Bonzini]

> Why?  Because in the first instance, m4 has to parse the big long string to 
> find the appropriate closing ], on every use of the macro, even though it 
> will 
> only be expanding the AC_REQUIRE_SHELL_FN once.  In the second instance, the 
> AC_REQUIRE line takes much less effort to parse than the full-blown shell 
> definition.
> 
> Yes, this probably means refactoring your entire series to use this idea, but 
> hopefully it proves to make autoconf even faster.

My first version was like that.  However it's complicated by the fact
that foo_fn would need to be invoked with a language argument (that's
the m4_require_with_args message I posted on address@hidden).  So, for
now it's easier to have the version that inherently slower, but in
practice still faster than what we have now.

Paolo