diff --git a/pkgs/tools/compression/xar/0001-Add-useless-descriptions-to-AC_DEFINE.patch b/pkgs/tools/compression/xar/0001-Add-useless-descriptions-to-AC_DEFINE.patch
new file mode 100644
index 000000000000..a605d2db1708
--- /dev/null
+++ b/pkgs/tools/compression/xar/0001-Add-useless-descriptions-to-AC_DEFINE.patch
@@ -0,0 +1,95 @@
+From a14be07c0aae3bf6f732d1ca5f625ba375702121 Mon Sep 17 00:00:00 2001
+From: Andrew Childs <andrew.childs@bibo.com.ph>
+Date: Sun, 15 Nov 2020 19:12:33 +0900
+Subject: [PATCH 1/2] Add useless descriptions to AC_DEFINE
+
+Removes autoheader warnings.
+---
+ configure.ac | 42 +++++++++++++++++++++---------------------
+ 1 file changed, 21 insertions(+), 21 deletions(-)
+
+diff --git a/configure.ac b/configure.ac
+index 812b5ff..358ab89 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -210,48 +210,48 @@ AC_CHECK_MEMBERS([struct stat.st_flags])
+ 
+ AC_CHECK_SIZEOF(uid_t)
+ if test $ac_cv_sizeof_uid_t = "4"; then
+-AC_DEFINE(UID_STRING, RId32)
+-AC_DEFINE(UID_CAST, (uint32_t))
++AC_DEFINE([UID_STRING], RId32, [UID_STRING])
++AC_DEFINE([UID_CAST], (uint32_t), [UID_CAST])
+ elif test $ac_cv_sizeof_uid_t = "8"; then
+-AC_DEFINE(UID_STRING, PRId64)
+-AC_DEFINE(UID_CAST, (uint64_t))
++AC_DEFINE([UID_STRING], PRId64, [UID_STRING])
++AC_DEFINE([UID_CAST], (uint64_t), [UID_CAST])
+ else
+ AC_ERROR(can not detect the size of your system's uid_t type)
+ fi
+ 
+ AC_CHECK_SIZEOF(gid_t)
+ if test $ac_cv_sizeof_gid_t = "4"; then
+-AC_DEFINE(GID_STRING, PRId32)
+-AC_DEFINE(GID_CAST, (uint32_t))
++AC_DEFINE([GID_STRING], PRId32, [GID_STRING])
++AC_DEFINE([GID_CAST], (uint32_t), [GID_CAST])
+ elif test $ac_cv_sizeof_gid_t = "8"; then
+-AC_DEFINE(GID_STRING, PRId64)
+-AC_DEFINE(GID_CAST, (uint64_t))
++AC_DEFINE([GID_STRING], PRId64, [GID_STRING])
++AC_DEFINE([GID_CAST], (uint64_t), [GID_CAST])
+ else
+ AC_ERROR(can not detect the size of your system's gid_t type)
+ fi
+ 
+ AC_CHECK_SIZEOF(ino_t)
+ if test $ac_cv_sizeof_ino_t = "4"; then
+-AC_DEFINE(INO_STRING, PRId32)
+-AC_DEFINE(INO_HEXSTRING, PRIx32)
+-AC_DEFINE(INO_CAST, (uint32_t))
++AC_DEFINE([INO_STRING], PRId32, [INO_STRING])
++AC_DEFINE([INO_HEXSTRING], PRIx32, [INO_HEXSTRING])
++AC_DEFINE([INO_CAST], (uint32_t), [INO_CAST])
+ elif test $ac_cv_sizeof_ino_t = "8"; then
+-AC_DEFINE(INO_STRING, PRId64)
+-AC_DEFINE(INO_HEXSTRING, PRIx64)
+-AC_DEFINE(INO_CAST, (uint64_t))
++AC_DEFINE([INO_STRING], PRId64, [INO_STRING])
++AC_DEFINE([INO_HEXSTRING], PRIx64, [INO_HEXSTRING])
++AC_DEFINE([INO_CAST], (uint64_t), [INO_CAST])
+ else
+ AC_ERROR(can not detect the size of your system's ino_t type)
+ fi
+ 
+ AC_CHECK_SIZEOF(dev_t)
+ if test $ac_cv_sizeof_dev_t = "4"; then
+-AC_DEFINE(DEV_STRING, PRId32)
+-AC_DEFINE(DEV_HEXSTRING, PRIx32)
+-AC_DEFINE(DEV_CAST, (uint32_t))
++AC_DEFINE([DEV_STRING], PRId32, [DEV_STRING])
++AC_DEFINE([DEV_HEXSTRING], PRIx32, [DEV_HEXSTRING])
++AC_DEFINE([DEV_CAST], (uint32_t), [DEV_CAST])
+ elif test $ac_cv_sizeof_dev_t = "8"; then
+-AC_DEFINE(DEV_STRING, PRId64)
+-AC_DEFINE(DEV_HEXSTRING, PRIx64)
+-AC_DEFINE(DEV_CAST, (uint64_t))
++AC_DEFINE([DEV_STRING], PRId64, [DEV_STRING])
++AC_DEFINE([DEV_HEXSTRING], PRIx64, [DEV_HEXSTRING])
++AC_DEFINE([DEV_CAST], (uint64_t), [DEV_CAST])
+ else
+ AC_ERROR(can not detect the size of your system's dev_t type)
+ fi
+@@ -261,7 +261,7 @@ AC_CHECK_LIB(acl, acl_get_file)
+ dnl Check for paths
+ AC_PREFIX_DEFAULT(/usr/local)
+ 
+-AC_CHECK_FUNC([asprintf], AC_DEFINE([HAVE_ASPRINTF]))
++AC_CHECK_FUNC([asprintf], AC_DEFINE([HAVE_ASPRINTF], [], [HAVE_ASPRINTF]))
+ 
+ dnl 
+ dnl Configure libxml2.
+-- 
+2.28.0
+
diff --git a/pkgs/tools/compression/xar/0002-Use-pkg-config-for-libxml2.patch b/pkgs/tools/compression/xar/0002-Use-pkg-config-for-libxml2.patch
new file mode 100644
index 000000000000..d71ad4b753c1
--- /dev/null
+++ b/pkgs/tools/compression/xar/0002-Use-pkg-config-for-libxml2.patch
@@ -0,0 +1,89 @@
+From 276833851657c85651c053ee16b8e1a8dc768a50 Mon Sep 17 00:00:00 2001
+From: Andrew Childs <andrew.childs@bibo.com.ph>
+Date: Sun, 15 Nov 2020 19:12:56 +0900
+Subject: [PATCH 2/2] Use pkg-config for libxml2
+
+---
+ configure.ac | 66 +++++++++-------------------------------------------
+ 1 file changed, 11 insertions(+), 55 deletions(-)
+
+diff --git a/configure.ac b/configure.ac
+index 358ab89..984a694 100644
+--- a/configure.ac
++++ b/configure.ac
+@@ -268,61 +268,17 @@ dnl Configure libxml2.
+ dnl 
+ LIBXML2_VERSION_MIN=2.6.11
+ 
+-have_libxml2="1"
+-
+-AC_ARG_WITH([xml2-config], [  --with-xml2-config      libxml2 config program],
+-if test "x${with_xml2_config}" = "xno" ; then
+-  XML2_CONFIG=
+-else
+-  XML2_CONFIG="${with_xml2_config}"
+-fi
+-,
+-  XML2_CONFIG=
+-)
+-if test "x${XML2_CONFIG}" != "x" ; then
+-   if test ! -x "${XML2_CONFIG}" ; then
+-     AC_MSG_ERROR([Unusable or missing xml2-config: ${XML2_CONFIG}])
+-   fi
+-else
+-  AC_PATH_PROG([XML2_CONFIG], [xml2-config], , [${PATH}])
+-  if test "x${XML2_CONFIG}" = "x" ; then
+-    AC_MSG_ERROR([Cannot configure without xml2-config])
+-  fi
+-fi
+-
+-dnl Make sure the version of libxml2 found is sufficient.
+-AC_MSG_CHECKING([for libxml >= ${LIBXML2_VERSION_MIN}])
+-LIBXML2_FOUND=`2>&1 ${XML2_CONFIG} --version`
+-LIBXML2_MAJOR=`echo ${LIBXML2_FOUND} | tr . " " | awk '{print $1}'`
+-LIBXML2_MINOR=`echo ${LIBXML2_FOUND} | tr . " " | awk '{print $2}' | tr a-z " " |awk '{print $1}'`
+-LIBXML2_BRANCH=`echo ${LIBXML2_FOUND} | tr . " " | awk '{print $3}' | tr a-z " " |awk '{print $1}'`
+-if test "x${LIBXML2_BRANCH}" = "x" ; then
+-  LIBXML2_BRANCH=0
+-fi
+-LIBXML2_MAJOR_MIN=`echo ${LIBXML2_VERSION_MIN} | tr . " " | awk '{print $1}'`
+-LIBXML2_MINOR_MIN=`echo ${LIBXML2_VERSION_MIN} | tr . " " | awk '{print $2}'`
+-LIBXML2_BRANCH_MIN=`echo ${LIBXML2_VERSION_MIN} | tr . " " | awk '{print $3}'`
+-if test ${LIBXML2_MAJOR} -gt ${LIBXML2_MAJOR_MIN} \
+-     -o ${LIBXML2_MAJOR} -eq ${LIBXML2_MAJOR_MIN} \
+-     -a ${LIBXML2_MINOR} -gt ${LIBXML2_MINOR_MIN} \
+-     -o ${LIBXML2_MAJOR} -eq ${LIBXML2_MAJOR_MIN} \
+-     -a ${LIBXML2_MINOR} -eq ${LIBXML2_MINOR_MIN} \
+-     -a ${LIBXML2_BRANCH} -ge $LIBXML2_BRANCH_MIN ; then
+-  AC_MSG_RESULT([${LIBXML2_MAJOR}.${LIBXML2_MINOR}.${LIBXML2_BRANCH}])
+-  have_libxml2="1"
+-  CPPFLAGS="${CPPFLAGS} `${XML2_CONFIG} --cflags`"
+-  LIBS="${LIBS} `${XML2_CONFIG} --libs`"
+-else
+-  AC_MSG_RESULT([no])
+-  have_libxml2="0"
+-fi
+-if test "x${have_libxml2}" = "x1" ; then
+-  dnl Final sanity check, to make sure that xmlwriter is present.
+-  AC_CHECK_HEADER([libxml/xmlwriter.h], , [have_libxml2="0"])
+-fi
+-if test "x${have_libxml2}" = "x0" ; then
+-  AC_MSG_ERROR([Cannot build without libxml2])
+-fi
++PKG_PROG_PKG_CONFIG
++
++PKG_CHECK_MODULES(LIBXML2_PKGCONFIG, [libxml-2.0 >= ${LIBXML2_VERSION_MIN}],
++  [
++    have_libxml2=1
++    CPPFLAGS="${CPPFLAGS} ${LIBXML2_PKGCONFIG_CFLAGS}"
++    LIBS="${LIBS} ${LIBXML2_PKGCONFIG_LIBS}"
++  ],
++  [
++    have_libxml2=0
++  ])
+ 
+ dnl 
+ dnl Configure libcrypto (part of OpenSSL).
+-- 
+2.28.0
+
diff --git a/pkgs/tools/compression/xar/default.nix b/pkgs/tools/compression/xar/default.nix
index 32b6c6d005cf..d4baab17b91f 100644
--- a/pkgs/tools/compression/xar/default.nix
+++ b/pkgs/tools/compression/xar/default.nix
@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchurl, libxml2, xz, openssl, zlib, bzip2, fts, autoconf }:
+{ lib, stdenv, fetchurl, pkg-config, libxml2, xz, openssl, zlib, bzip2, fts, autoreconfHook }:
 
 stdenv.mkDerivation rec {
   version = "1.6.1";
@@ -9,16 +9,20 @@ stdenv.mkDerivation rec {
     sha256 = "0ghmsbs6xwg1092v7pjcibmk5wkyifwxw6ygp08gfz25d2chhipf";
   };
 
-  buildInputs = [ libxml2 xz openssl zlib bzip2 fts autoconf ];
+  nativeBuildInputs = [ autoreconfHook pkg-config ];
+  buildInputs = [ libxml2 xz openssl zlib bzip2 fts ];
 
-  prePatch = ''
+  patches = [
+    ./0001-Add-useless-descriptions-to-AC_DEFINE.patch
+    ./0002-Use-pkg-config-for-libxml2.patch
+  ];
+
+  postPatch = ''
     substituteInPlace configure.ac \
       --replace 'OpenSSL_add_all_ciphers' 'OPENSSL_init_crypto' \
       --replace 'openssl/evp.h' 'openssl/crypto.h'
   '';
 
-  preConfigure = "./autogen.sh";
-
   meta = {
     homepage    = "https://mackyle.github.io/xar/";
     description = "Extensible Archiver";