This patch removes the _XOPEN_SOURCE preprocessor directive as it does not seem to be needed.
Setting it removes the definition of strdup, which is used in filter-datatypes.c.

Patch by Roel Janssen <roel@gnu.org>
*** a/src/frontend/filter-datatypes.c	1970-01-01 01:00:00.000000000 +0100
--- b/src/frontend/filter-datatypes.c	2018-04-03 17:39:23.177905592 +0200
***************
*** 18,24 ****
   *  Copyright (C) 2006 Steve Harris for Garlik
   */
  
- #define _XOPEN_SOURCE
  #include <stdlib.h>
  #include <string.h>
  #include <math.h>
--- 18,23 ----
ype='hidden' name='id' value='4c5edee1ef2aff2b8f3782ccb03723a6428bf600'/><select name='h' onchange='this.form.submit();'>
<option value='koszko' selected='selected'>koszko</option>
<option value='koszko-scripts'>koszko-scripts</option>
</select> <input type='submit' value='switch'/></form></td></tr>
<tr><td class='sub'>Wojtek's customized Guix</td><td class='sub right'></td></tr></table>
<table class='tabs'><tr><td>
<a href='/guix/about/'>about</a><a href='/guix/'>summary</a><a href='/guix/refs/?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600'>refs</a><a class='active' href='/guix/log/bootstrap'>log</a><a href='/guix/tree/bootstrap?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600'>tree</a><a href='/guix/commit/bootstrap?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600'>commit</a><a href='/guix/diff/bootstrap?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600'>diff</a></td><td class='form'><form class='right' method='get' action='/guix/log/bootstrap'>
<input type='hidden' name='id' value='4c5edee1ef2aff2b8f3782ccb03723a6428bf600'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600'>root</a>/<a href='/guix/log/bootstrap?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600'>bootstrap</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/bootstrap?id=4c5edee1ef2aff2b8f3782ccb03723a6428bf600&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2020-02-17 11:49:08 +0100'>2020-02-17</span></td><td><a href='/guix/commit/bootstrap?id=3dd311e3a059131ef245417106d4fb659222ef3c'>bootstrap: Fix typo.</a><span class='msg-avail'>...<span class='msg-tooltip'>* bootstrap: Substitute ‘guix-cookbook’ for copy/pasted ‘guix-manual’.

Reported-by: jetomit on #guix
</span></span></td><td>Tobias Geerinckx-Rice</td></tr>
<tr><td><span title='2019-09-18 11:38:14 +0200'>2019-09-18</span></td><td><a href='/guix/commit/bootstrap?id=7bc46ecc34ceb042ff890e5d306d0a2a736e891d'>doc: Add Guix Cookbook.</a><span class='msg-avail'>...<span class='msg-tooltip'>* .gitignore: Update ignore list.
* Makefile.am (assert-no-store-file-names): Exclude the cookbook.
* bootstrap: Generate po files for cookbook translations.
* doc/guix-cookbook.texi: New file.
* doc/local.mk (info_TEXINFOS): Add it; add a rule to build cookbook
translations.
* po/doc/local.mk (DOC_COOKBOOK_PO_FILES): New variable.
(EXTRA_DIST): Add cookbook pot file and po files.
(doc-po-update-cookbook-%): New target.
(doc-pot-update): Also update cookbook pot file.
(doc-po-update): Also update cookbook po files.
</span></span></td><td>Ricardo Wurmus</td></tr>
<tr><td><span title='2019-04-26 11:21:32 +0200'>2019-04-26</span></td><td><a href='/guix/commit/bootstrap?id=9ca5ff882e2ac4eaab02eb0fde545bd784af478b'>bootstrap: Break automake dependency on generated files.</a><span class='msg-avail'>...<span class='msg-tooltip'>* bootstrap: Generate stub files for the manual translations whose
generated files are not included in the VCS.
* doc/contributing.de.texi: Remove file.
* doc/contributing.es.texi: Remove file.
* doc/contributing.fr.texi: Remove file.
* doc/contributing.zh_CN.texi: Remove file.
* doc/guix.de.texi: Remove file.
* doc/guix.es.texi: Remove file.
* doc/guix.fr.texi: Remove file.
* doc/guix.zh_CN.texi: Remove file.
* .gitignore: Add them.

Signed-off-by: Julien Lepiller &lt;julien@lepiller.eu&gt;
</span></span></td><td>Miguel Ángel Arruga Vivas</td></tr>
Courtès</td></tr>
<tr><td><span title='2022-05-23 16:24:46 +0200'>2022-05-23</span></td><td><a href='/guix/commit/tests/guix-package.sh?id=aaf547824e389b68c028c9b3fd4d15fd2991dc31'>scripts: package: Transform before creating manifest entries.</a><span class='msg-avail'>...<span class='msg-tooltip'>* guix/scripts/package.scm (options-&gt;installable): Add TRANSFORM
argument, to be able to directly transform the new packages before
creating their manifest entries.
(process-actions): Remove transform-entry, and step3, transforming
directly in step2.
* tests/guix-package.sh: Add test.

Signed-off-by: Ludovic Courtès &lt;ludo@gnu.org&gt;
</span></span></td><td>Josselin Poiret</td></tr>
<tr><td><span title='2022-02-18 14:14:38 +0100'>2022-02-18</span></td><td><a href='/guix/commit/tests/guix-package.sh?id=5a57313918a5c1bd5cf8238c2dcae64a03523952'>profiles: 'profile-derivation' rejects unsupported packages.</a><span class='msg-avail'>...<span class='msg-tooltip'>Previously user-facing commands would happily start building packages
even if they do not support that system.  With this change, all the
user-facing commands reject unsupported packages without going further.

* guix/profiles.scm (profile-derivation): Add #:allow-unsupported-packages?.
Define 'check-supported-packages' and honor #:allow-unsupported-packages?.
* tests/guix-pack.sh, tests/guix-package.sh, tests/guix-shell.sh: Ensure
that unsupported packages are rejected.
* tests/guix-system.sh: Pass "--system=armhf-linux" when attempting to
build gnu/system/examples/asus-c201.tmpl.
</span></span></td><td>Ludovic Courtès</td></tr>