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Re: Fix chdir-long.m4 caching
From: |
Eric Blake |
Subject: |
Re: Fix chdir-long.m4 caching |
Date: |
Sat, 30 Sep 2006 07:59:15 -0600 |
User-agent: |
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.0.7) Gecko/20060909 Thunderbird/1.5.0.7 Mnenhy/0.7.4.666 |
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According to Stepan Kasal on 9/29/2006 8:46 AM:
> So I did the one line change to AS_LITERAL_IF, did many changes in
> the indirect callers of it, and wrote a test case.
>
> The resulting patch is attached here.
Thanks for all that effort. I agree with your reasoning and testing
approach, and the patch appears to be correct to me. Is there any
documentation we need to update as a result, just in case there is a rare
compatibility problem? And I would feel comfortable getting more than
just my opinion before applying this patch, as it touches a rather
fundamental low-level piece of autoconf.
>
> Can this bring some backward compatibility problems?
Perhaps if the macro has side-effects, although that is bad style:
m4_define([count], [0])
m4_define([ac_var], [m4_pushdef([count],
m4_incr(count))ac_cv_side_effect_counter])
# this would only bump count once, since we did the expansion early
AC_CACHE_CHECK([for something], ac_var)
# but how many times is count bumped here? I think it is different pre-
# and post-patch, because the text ac_var gets output multiple times,
# and each output is then expanded during rescanning.
AC_CACHE_CHECK([for something else], [ac_var])
But I don't see any evidence of real-life autoconf macros this perverted,
where the user cares about the final value of count.
> As I said before, I hope the problems should be rare.
I hope so too.
- --
Life is short - so eat dessert first!
Eric Blake address@hidden
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- Re: Fix chdir-long.m4 caching, (continued)
- Re: Fix chdir-long.m4 caching, Stepan Kasal, 2006/09/26
- Re: Fix chdir-long.m4 caching, Ralf Wildenhues, 2006/09/26
- Re: Fix chdir-long.m4 caching, Eric Blake-1, 2006/09/26
- Re: Fix chdir-long.m4 caching, Eric Blake, 2006/09/26
- Re: Fix chdir-long.m4 caching, Ralf Wildenhues, 2006/09/27
- Re: Fix chdir-long.m4 caching, Eric Blake-1, 2006/09/27
- Re: Fix chdir-long.m4 caching, Stepan Kasal, 2006/09/29
- Re: Fix chdir-long.m4 caching, Eric Blake, 2006/09/30
- Re: Fix chdir-long.m4 caching, Stepan Kasal, 2006/09/27
- Re: Fix chdir-long.m4 caching, Stepan Kasal, 2006/09/29
- Re: Fix chdir-long.m4 caching,
Eric Blake <=