Re: [PATCH] use m4_require to implement AS_REQUIRE

[Paolo Bonzini]

>>    ver      usertime   size
>>    2.61     18.154s    1037578
>>    2.63     13.192s    1055693
>>    +funcs1  13.907s    886574
>>    +funcs2  11.467s    780238
> 
> I take it these are speedups in 'autoconf' time, and not in 'configure' time?

Yes, of course.

>>  # BODY-TO-EXPAND is some initialization which must be expanded in the
>> -# given diversion when expanded (required or not).  This is very
>> -# different from m4_require.  For instance:
>> +# given diversion when expanded (required or not).  The expansion
>> +# goes in the named diversion or an earlier one.
> 
> Hmmm.  M4SH-INIT is at diversion 6.  If this is identical to m4_require,
> then it doesn't take very many nested AS_REQUIRES before we have dropped
> to diversion 0, or even worse to diversion -1.

No, the required macros are built into the _m4_divert_grow diversions,
that count down from 10000, and dumped "atomically" into the
_m4_divert_dump diversion (for m4_require) or into the specified
diversion (for m4_divert_require).

>> +m4_defun([AS_REQUIRE],
>> +[m4_define([_m4_divert_desired], m4_default_quoted([$3], [M4SH-INIT]))dnl
>> +m4_if(m4_eval(_m4_divert(_m4_divert_dump) <= 
>> _m4_divert(_m4_divert_desired)), 1,
> 
> Or maybe this eval is trying to guarantee just that?  Again, I'm typing
> this without a thorough review; it is just first impressions.

The eval is basically subsuming 926ed6a97561e0a77de18011b29c6bcaaff4c365
(place _AS_UNSET_PREPARE in the right diversion): if the outermost macro
is expanded before the requested diversion, we do not move its shell
requirements to M4SH-INIT or M4SH-INIT-FN.

>> @@ -1698,7 +1713,7 @@ m4_provide_if([$1],
>>            [],
>>            [m4_warn([syntax],
>>                     [$1 is m4_require'd but not m4_defun'd])])]],
>> -      [[m4_divert(_m4_defn([_m4_divert_dump]))]],
>> +      [[m4_divert($3)]],
> 
> Underquoted?

Assuming that the existing code was not underquoted, then either I
underquote here, or I do that in m4_require.  I chose to underquote
here.  I can try the other version, underquoting the _m4_defn in
m4_require and using [$3] here.

Paolo