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Re: [PATCH 0/2] Modernize header checks

From: Russ Allbery
Subject: Re: [PATCH 0/2] Modernize header checks
Date: Fri, 31 May 2013 09:39:53 -0700
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/23.4 (gnu/linux)

Zack Weinberg <address@hidden> writes:

> Second, it cleans up AC_INCLUDES_DEFAULT and all the other canned
> tests so that they don't waste time checking for ISO C90 headers,
> which are now ubiquitous (stddef.h, stdlib.h, string.h, wchar.h,
> wctype.h, locale.h, time.h) and don't use pre-standard headers that
> were replaced by C90 headers at all (memory.h and strings.h).

I *think* your patch would remove strings.h from the list of headers that
are probed by default by Autoconf, and hence remove HAVE_STRINGS_H from
the preprocessor directives set by Autoconf.

If so, note that removing strings.h from the list of headers that are
probed by default will cause backwards compatibility issues.  One still
must include strings.h (not string.h) according to POSIX in order to get
strcasecmp and friends, and some operating systems (specifically at least
some versions of FreeBSD) do actually enforce that and do not prototype
those functions in string.h.  I'm quite sure there is code out there that
assumes that Autoconf will probe for strings.h as a side effect of other
probes and set HAVE_STRINGS_H, and therefore doesn't probe for it
explicitly.  (I maintain some of it, in fact.)

Russ Allbery (address@hidden)             <>

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