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From: | Paul Eggert |
Subject: | Re: [PATCH] Don’t use AC_EGREP_CPP if affected by CFLAGS |
Date: | Mon, 6 Nov 2017 16:08:37 -0800 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
On 11/06/2017 11:23 AM, Bruno Haible wrote:
(2) would be better than what we have now, yes. But how could such a check be implemented robustly? Wouldn't it require a comprehensive knowledge of which compiler options affect which predefined macros on which platforms?When the error rate is so high, we should 1) improve the documentation (this is mainly install.texi from Autoconf), 2) add a consistency check in AC_PROG_CC or AC_PROG_CPP.
The problem is not limited to flags like -m32 and -m64. Flags like -fsanitize=address can also affect preprocessor behavior. A complete list of such flags would be daunting to maintain.
In contrast, it's relatively simple to say "Don't use AC_EGREP_CPP unless you know the result isn't likely to depend on compiler options."
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