The Tor Browser / file revision

 dnl This Source Code Form is subject to the terms of the Mozilla Public

 dnl dnl License, v. 2.0. If a copy of the MPL was not distributed with this

 dnl dnl file, You can obtain one at http://mozilla.org/MPL/2.0/.

 dnl Set of hotfixes to address issues in autoconf 2.13

 dnl Divert AC_CHECK_FUNC so that the #includes it uses can't interfere

 dnl with the function it tests.

 dnl So, when testing e.g. posix_memalign, any #include that AC_CHECK_FUNC

 dnl prints is replaced with:

 dnl   #define posix_memalign innocuous_posix_memalign

 dnl   #include "theinclude"

 dnl   #undef posix_memalign

 dnl This avoids double declaration of that function when the header normally

 dnl declares it, while the test itself is just expecting the function not to be

 dnl declared at all, and declares it differently (which doesn't matter for the

 dnl test itself).

 dnl More recent versions of autoconf are essentially doing this.

 define([ac_cv_func_], [ac_cv_func2_])dnl

 define([_AC_CHECK_FUNC],defn([AC_CHECK_FUNC]))dnl

 define([AC_CHECK_FUNC], [dnl

 patsubst(_AC_CHECK_FUNC($@), [#include.*$], [#define $1 innocuous_$1

 \&

 #undef $1])])dnl