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Re: spurious "(cached)" output from AC_CACHE_VAL
From: |
Eric Blake |
Subject: |
Re: spurious "(cached)" output from AC_CACHE_VAL |
Date: |
Sat, 28 Feb 2009 06:45:06 -0700 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.19) Gecko/20081209 Thunderbird/2.0.0.19 Mnenhy/0.7.6.666 |
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According to Bruno Haible on 2/27/2009 3:36 PM:
>
> Eric Blake wrote in
> <http://lists.gnu.org/archive/html/bug-gnulib/2009-02/msg00213.html>:
>> But your patch has merit in that it makes a nice macro name that explains
>> what
>> you are intending.
>
> It would even be better if this macro was not needed. Couldn't AC_CACHE_VAL be
> changed to output "(cached)" when run between AC_MSG_CHECKING and
> AC_MSG_RESULT, and be silent otherwise?
Wow, nice suggestion for improving the API. I'll work on that.
>
> The implementation of this change would be that AC_CACHE_VAL invokes a
> macro made for this purpose, say, _AC_ECHO_CACHED. AC_MSG_CHECKING would
> pushdef _AC_ECHO_CACHED to a definition that expands to nothing or a ':'
> command, and AC_MSG_RESULT would popdef it.
Or, even better, AC_MSG_CHECKING pushdef's a witness macro, AC_MSG_RESULT
pops it, and AC_CACHE_VAL checks whether the witness macro is defined, to
avoid the AS_ECHO altogether (no need to output a no-op : into the
resulting script).
>> If you'd like, I'll even add another sentence to the autoconf manual that
>> makes
>> it clear that all such variables with this naming scheme, regardless of how
>> they are used, are cached.
>
> I would *not* document this. If you document it, it may cause additional
> effort
> if you or Ralf want to change the implementation of caching, sometime in the
> future. There is no functional benefit for the user either: users can use
> AC_CACHE_VAL.
Thanks to your suggestion of an improved API for AC_CACHE_VAL, I'm
inclined to agree that we no longer need to worry about documenting that
all _cv_ variables are cached, leaving some flexibility for under-the-hood
improvements.
- --
Don't work too hard, make some time for fun as well!
Eric Blake address@hidden
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- computing long double NaN on Irix 6.5, Eric Blake, 2009/02/26
- Re: computing long double NaN on Irix 6.5, Eric Blake, 2009/02/26
- Re: computing long double NaN on Irix 6.5, Bruno Haible, 2009/02/27
- spurious roundl output (was: computing long double NaN on Irix 6.5), Eric Blake, 2009/02/27
- Re: spurious roundl output (was: computing long double NaN on Irix 6.5), Bruno Haible, 2009/02/27
- Re: spurious roundl output (was: computing long double NaN on Irix 6.5), Eric Blake, 2009/02/27
- Re: spurious "(cached)" output from AC_CACHE_VAL, Bruno Haible, 2009/02/27
- Re: spurious "(cached)" output from AC_CACHE_VAL,
Eric Blake <=
- Re: spurious "(cached)" output from AC_CACHE_VAL, Ralf Wildenhues, 2009/02/28
- Re: computing long double NaN on Irix 6.5, Eric Blake, 2009/02/27
- Re: gcc on Irix 6.5, Bruno Haible, 2009/02/27
Re: computing long double NaN on Irix 6.5, Tom G. Christensen, 2009/02/27