Initial commit

17 files changed, 1776 insertions, 0 deletions

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..9e096c8
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,31 @@
+# Swap and backup files
+*.s[a-w]?
+*.vim
+*~
+*.orig
+
+# Files generated by aclocal, autoconf, and automake
+/aclocal.m4
+/autom4te.cache/
+/configure
+/config.h.in
+/build-aux/
+/ChangeLog
+/INSTALL
+Makefile.in
+
+# Files generated by configure
+/config.log
+/config.status
+Makefile
+/config.h
+/stamp-h1
+
+# Files generated by Makefile
+.deps
+.dirstamp
+*.o
+/version.c
+/@
+/atsign-*.tar*
+/atsign-*/
diff --git a/AUTHORS b/AUTHORS
new file mode 100644
index 0000000..d9952b7
--- /dev/null
+++ b/AUTHORS
@@ -0,0 +1 @@
+P. J. McDermott <pj@pehjota.net>
diff --git a/COPYING b/COPYING
new file mode 100644
index 0000000..f288702
--- /dev/null
+++ b/COPYING
@@ -0,0 +1,674 @@
+                    GNU GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <https://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+                            Preamble
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+GNU General Public License, you may choose any version ever published
+by the Free Software Foundation.
+
+  If the Program specifies that a proxy can decide which future
+versions of the GNU General Public License can be used, that proxy's
+public statement of acceptance of a version permanently authorizes you
+to choose that version for the Program.
+
+  Later license versions may give you additional or different
+permissions.  However, no additional obligations are imposed on any
+author or copyright holder as a result of your choosing to follow a
+later version.
+
+  15. Disclaimer of Warranty.
+
+  THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY
+APPLICABLE LAW.  EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT
+HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY
+OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO,
+THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+PURPOSE.  THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM
+IS WITH YOU.  SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF
+ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
+
+  16. Limitation of Liability.
+
+  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING
+WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS
+THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY
+GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE
+USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF
+DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD
+PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS),
+EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF
+SUCH DAMAGES.
+
+  17. Interpretation of Sections 15 and 16.
+
+  If the disclaimer of warranty and limitation of liability provided
+above cannot be given local legal effect according to their terms,
+reviewing courts shall apply local law that most closely approximates
+an absolute waiver of all civil liability in connection with the
+Program, unless a warranty or assumption of liability accompanies a
+copy of the Program in return for a fee.
+
+                     END OF TERMS AND CONDITIONS
+
+            How to Apply These Terms to Your New Programs
+
+  If you develop a new program, and you want it to be of the greatest
+possible use to the public, the best way to achieve this is to make it
+free software which everyone can redistribute and change under these terms.
+
+  To do so, attach the following notices to the program.  It is safest
+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
+the "copyright" line and a pointer to where the full notice is found.
+
+    <one line to give the program's name and a brief idea of what it does.>
+    Copyright (C) <year>  <name of author>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.
diff --git a/Makefile.am b/Makefile.am
new file mode 100644
index 0000000..8cc00e8
--- /dev/null
+++ b/Makefile.am
@@ -0,0 +1,114 @@
+# Process this file with automake to produce an input makefile.
+#
+# Copyright (C) 2013, 2014, 2017, 2018, 2021  P. J. McDermott
+#
+# This file is part of @
+#
+# @ is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# @ is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with @.  If not, see <http://www.gnu.org/licenses/>.
+
+KEY = 'B47A 6674 80CD A1F8 361B  31EE FCDF 9F3F B5D7 3216'
+
+if IN_GIT
+PACKAGE_VERSION_GIT = $$(printf ' (%s)' \
+	"$$({ git describe --tags --dirty 2>/dev/null || \
+		printf '%s-g%s' \
+			"$$(git rev-list --count HEAD)" \
+			"$$(git describe --tags --dirty --always)"; \
+	} | sed 's|^.*/||')")
+else
+PACKAGE_VERSION_GIT =
+endif
+
+# PACKAGE_STRING is used in the test suite output and log.
+# PACKAGE_VERSION can't be overridden.  Automake ignores it in the IN_GIT
+# conditional (and throws a warning), and setting it to $(PACKAGE_VERSION_GIT)
+# outside the conditional causes PACKAGE_VERSION_GIT to reference itself.
+# VERSION is not set here because it is used by:
+#   * Automake's distdir macro
+#   * Automake's distdir target (which checks for $(VERSION) in NEWS)
+#   * Our release target
+PACKAGE_STRING = $(PACKAGE_NAME) $(PACKAGE_VERSION)$(PACKAGE_VERSION_GIT)
+
+bin_PROGRAMS = @
+
+@_SOURCES =
+@_CFLAGS = \
+	$(WARN_CFLAGS) \
+	$(ASAN_CFLAGS)
+@_CPPFLAGS = \
+	$(SDL_CFLAGS) \
+	$(SDL_TTF_CFLAGS) \
+	-DABS_BUILDDIR=\"$(abs_builddir)\" \
+	-DFONTSDIR=\"$(fontsdir)\"
+@_LDADD = \
+	$(ASAN_CFLAGS) \
+	$(SDL_LIBS) \
+	$(SDL_TTF_LIBS)
+@_LINK = $(LINK) version.c
+EXTRA_@_DEPENDENCIES = version.c $(DATA)
+CLEANFILES = version.c
+CONFIG_CLEAN_FILES =
+EXTRA_DIST = autogen.sh
+
+V_REDIR = $(V_REDIR_$(V))
+V_REDIR_ = $(V_REDIR_$(AM_DEFAULT_VERBOSITY))
+V_REDIR_0 = 1>/dev/null 2>&1
+V_REDIR_1 =
+
+version.c: $(@_OBJECTS) $(@_DEPENDENCIES)
+	$(AM_V_GEN)printf 'const char *PACKAGE_VERSION_GIT = "%s";\n' \
+		"$(PACKAGE_VERSION_GIT)" >version.c
+
+really-clean: distclean
+	rm -Rf $(srcdir)/aclocal.m4 $(srcdir)/autom4te.cache/ \
+		$(srcdir)/configure \
+		$(srcdir)/config.h.in \
+		$(srcdir)/build-aux/ $(srcdir)/INSTALL $(srcdir)/Makefile.in \
+		$(srcdir)/ChangeLog
+
+dist-hook:
+	set -e; \
+	if [ -d '$(srcdir)/.git' ]; then \
+		printf 'Generated file.  Do not edit.\n\n' \
+			>'$(distdir)/ChangeLog~'; \
+		GIT_DIR='$(srcdir)/.git' git log --stat --color=never \
+			>>'$(distdir)/ChangeLog~'; \
+		mv '$(distdir)/ChangeLog~' '$(distdir)/ChangeLog'; \
+	fi
+
+release:
+	sed "s/^Released: ????-??-??\$$/Released: $$(date '+%Y-%m-%d')/" \
+		'$(srcdir)/NEWS' >'$(srcdir)/NEWS~'
+	mv '$(srcdir)/NEWS~' '$(srcdir)/NEWS'
+	$(MAKE) distcheck
+	set -e; \
+	export GIT_DIR='$(srcdir)/.git'; \
+	export GIT_WORK_TREE='$(srcdir)'; \
+	git commit -m 'NEWS: Release $(PACKAGE) $(VERSION)' -- NEWS; \
+	git tag '$(PACKAGE)/$(VERSION)' HEAD; \
+	git push --tags origin master:master
+	md5sum $(DIST_ARCHIVES) >MD5SUMS
+	sha256sum $(DIST_ARCHIVES) >SHA256SUMS
+	set -e; \
+	sigs=''; \
+	for f in $(DIST_ARCHIVES); do \
+		gpg --local-user $(KEY) --armor --detach-sign $${f}; \
+		sigs="$${sigs} $${f}.asc"; \
+	done; \
+	ssh files@files.pehjota.net mkdir -p files/pub/$(PACKAGE); \
+	rsync -az --progress --stats $(DIST_ARCHIVES) $${sigs} \
+		MD5SUMS SHA256SUMS \
+		files@files.pehjota.net:files/pub/$(PACKAGE)/$(VERSION)/
+
+include $(top_srcdir)/src/local.mk
diff --git a/NEWS b/NEWS
new file mode 100644
index 0000000..6106a4e
--- /dev/null
+++ b/NEWS
@@ -0,0 +1,16 @@
+@ version 0.1.0
+---------------
+
+Released: ????-??-??
+
+This is the initial release of @, in development since 2021-08-28.
+
+Copyright Information
+---------------------
+
+Copyright (C) 2021  P. J. McDermott
+
+Copying and distribution of this file, with or without modification,
+are permitted in any medium without royalty provided the copyright
+notice and this notice are preserved.  This file is offered as-is,
+without any warranty.
diff --git a/README b/README
new file mode 100644
index 0000000..c953475
--- /dev/null
+++ b/README
@@ -0,0 +1,17 @@
+@ (At Sign)
+-----------
+
+@ waits and exits at a specified time.  It can be used to delay shell
+commands, e.g.:
+
+    @ 18:00; printf '\a'
+
+Copyright
+---------
+
+Copyright (C) 2021  P. J. McDermott
+
+Copying and distribution of this file, with or without modification,
+are permitted in any medium without royalty provided the copyright
+notice and this notice are preserved.  This file is offered as-is,
+without any warranty.
diff --git a/autogen.sh b/autogen.sh
new file mode 100755
index 0000000..c80fde1
--- /dev/null
+++ b/autogen.sh
@@ -0,0 +1,28 @@
+#!/bin/sh
+#
+# Script to generate the build system.
+#
+# Copyright (C) 2013  P. J. McDermott
+#
+# Copying and distribution of this file, with or without modification,
+# are permitted in any medium without royalty provided the copyright
+# notice and this notice are preserved.  This file is offered as-is,
+# without any warranty.
+
+set -e
+
+srcdir="${0%/*}"
+
+{(
+	cd "${srcdir}"
+	[ -d build-aux ] || mkdir build-aux
+	cat >ChangeLog <<-EOF
+This file is generated upon release.  Run \`git log\` for a list of changes.
+EOF
+	aclocal
+	autoconf
+	autoheader
+	automake --add-missing --copy
+)}
+
+"${srcdir}/configure" "${@}"
diff --git a/configure.ac b/configure.ac
new file mode 100644
index 0000000..7e72e6d
--- /dev/null
+++ b/configure.ac
@@ -0,0 +1,111 @@
+# Process this file with autoconf to produce a configure script.
+#
+# Copyright (C) 2013, 2017, 2019, 2021  P. J. McDermott
+#
+# This file is part of @
+#
+# @ is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# @ is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with @.  If not, see <http://www.gnu.org/licenses/>.
+
+AC_INIT([@], [0.1.0], [mailto:pj@pehjota.net], [atsign])
+AC_CONFIG_AUX_DIR([build-aux])
+AC_CONFIG_MACRO_DIR([m4])
+AC_CONFIG_SRCDIR([src/main.c])
+
+AM_INIT_AUTOMAKE([gnu check-news dist-bzip2 dist-xz subdir-objects])
+AM_SILENT_RULES([yes])
+
+AM_CONDITIONAL([IN_GIT],
+	[test -d "${srcdir}/.git" && command -v git >/dev/null 2>&1])
+
+AM_CONDITIONAL([OUT_OF_TREE], [test x"${srcdir}" != x'.' ])
+
+save_CFLAGS="${CFLAGS-}"
+AC_PROG_CC()
+AM_PROG_CC_C_O()
+test -d "${srcdir}/.git" || CFLAGS="${save_CFLAGS}"
+
+funcs_missing=false
+AC_CHECK_FUNCS(
+	[\
+	],
+	[],
+	[funcs_missing=true])
+if ${funcs_missing}; then
+	AC_MSG_ERROR([required functions are missing])
+fi
+
+AX_CFLAGS_WARN_ALL()  dnl Adds -Wall or equivalent
+AX_CHECK_COMPILE_FLAG([-Wpedantic], [AX_APPEND_FLAG([-Wpedantic])])
+AX_CHECK_COMPILE_FLAG([-Wextra],    [AX_APPEND_FLAG([-Wextra])])
+
+AC_ARG_ENABLE([gcc-warnings],
+	[AS_HELP_STRING([--enable-gcc-warnings], [turn on many GCC warnings])],
+	[case "${enableval}" in yes|no) gcc_warnings=${enableval};;
+		*) AC_MSG_ERROR(
+			[bad value ${enableval} for gcc-warnings option]);;
+	esac],
+	[
+		gcc_warnings=no
+		test -d "${srcdir}/.git" && gcc_warnings=yes
+	]
+)
+if test "x${gcc_warnings}" = 'xyes'; then
+	nowarns=''
+	nowarns="${nowarns} -Wsystem-headers"
+	gl_MANYWARN_ALL_GCC([warns])
+	gl_MANYWARN_COMPLEMENT([warns], [${warns}], [${nowarns}])
+	for warn in ${warns}; do
+		gl_WARN_ADD([${warn}])
+	done
+	AC_SUBST([WARN_CFLAGS])
+fi
+
+AX_CHECK_COMPILE_FLAG([-fdiagnostics-color=auto],
+	[AX_APPEND_FLAG([-fdiagnostics-color=auto])])
+
+AC_ARG_ENABLE([address-sanitization],
+	[AS_HELP_STRING([--enable-address-sanitization],
+		[turn on AddressSanitizer (if available)])],
+	[case "${enableval}" in yes|no) address_sanitization=${enableval};;
+		*) AC_MSG_ERROR(
+			[bad value ${enableval} for address-sanitization option]
+			);;
+	esac],
+	[
+		address_sanitization=no
+		gl_GCC_VERSION_IFELSE([4], [8],
+			[test -d "${srcdir}/.git" && address_sanitization=yes])
+	]
+)
+if test "x${address_sanitization}" = 'xyes'; then
+	AX_CHECK_COMPILE_FLAG([-fsanitize=address],
+		[AX_APPEND_FLAG([-fsanitize=address], [ASAN_CFLAGS])])
+	AX_CHECK_COMPILE_FLAG([-fno-omit-frame-pointer],
+		[AX_APPEND_FLAG([-fno-omit-frame-pointer], [ASAN_CFLAGS])])
+	AC_SUBST([ASAN_CFLAGS])
+fi
+
+if ! test -d "${srcdir}/.git"; then
+	AX_CHECK_COMPILE_FLAG([-s], [AX_APPEND_FLAG([-s])])
+fi
+for flag in -Os -fno-unwind-tables -fno-asynchronous-unwind-tables \
+		-ffunction-sections -fdata-sections -Wl,--gc-sections \
+		-fstack-protector-strong -flto \
+		-Wl,-z,now -Wl,--hash-style=sysv -Wl,--build-id=none; do
+	AX_CHECK_COMPILE_FLAG([${flag}], [AX_APPEND_FLAG([${flag}])])
+done
+
+AC_CONFIG_FILES([Makefile])
+AC_CONFIG_HEADERS([config.h])
+AC_OUTPUT()
diff --git a/m4/ax_append_flag.m4 b/m4/ax_append_flag.m4
new file mode 100644
index 0000000..e8c5312
--- /dev/null
+++ b/m4/ax_append_flag.m4
@@ -0,0 +1,71 @@
+# ===========================================================================
+#      https://www.gnu.org/software/autoconf-archive/ax_append_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_APPEND_FLAG(FLAG, [FLAGS-VARIABLE])
+#
+# DESCRIPTION
+#
+#   FLAG is appended to the FLAGS-VARIABLE shell variable, with a space
+#   added in between.
+#
+#   If FLAGS-VARIABLE is not specified, the current language's flags (e.g.
+#   CFLAGS) is used.  FLAGS-VARIABLE is not changed if it already contains
+#   FLAG.  If FLAGS-VARIABLE is unset in the shell, it is set to exactly
+#   FLAG.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 7
+
+AC_DEFUN([AX_APPEND_FLAG],
+[dnl
+AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_SET_IF
+AS_VAR_PUSHDEF([FLAGS], [m4_default($2,_AC_LANG_PREFIX[FLAGS])])
+AS_VAR_SET_IF(FLAGS,[
+  AS_CASE([" AS_VAR_GET(FLAGS) "],
+    [*" $1 "*], [AC_RUN_LOG([: FLAGS already contains $1])],
+    [
+     AS_VAR_APPEND(FLAGS,[" $1"])
+     AC_RUN_LOG([: FLAGS="$FLAGS"])
+    ])
+  ],
+  [
+  AS_VAR_SET(FLAGS,[$1])
+  AC_RUN_LOG([: FLAGS="$FLAGS"])
+  ])
+AS_VAR_POPDEF([FLAGS])dnl
+])dnl AX_APPEND_FLAG
diff --git a/m4/ax_cflags_warn_all.m4 b/m4/ax_cflags_warn_all.m4
new file mode 100644
index 0000000..094577e
--- /dev/null
+++ b/m4/ax_cflags_warn_all.m4
@@ -0,0 +1,122 @@
+# ===========================================================================
+#    https://www.gnu.org/software/autoconf-archive/ax_cflags_warn_all.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CFLAGS_WARN_ALL   [(shellvar [,default, [A/NA]])]
+#   AX_CXXFLAGS_WARN_ALL [(shellvar [,default, [A/NA]])]
+#   AX_FCFLAGS_WARN_ALL  [(shellvar [,default, [A/NA]])]
+#
+# DESCRIPTION
+#
+#   Try to find a compiler option that enables most reasonable warnings.
+#
+#   For the GNU compiler it will be -Wall (and -ansi -pedantic) The result
+#   is added to the shellvar being CFLAGS, CXXFLAGS, or FCFLAGS by default.
+#
+#   Currently this macro knows about the GCC, Solaris, Digital Unix, AIX,
+#   HP-UX, IRIX, NEC SX-5 (Super-UX 10), Cray J90 (Unicos 10.0.0.8), and
+#   Intel compilers.  For a given compiler, the Fortran flags are much more
+#   experimental than their C equivalents.
+#
+#    - $1 shell-variable-to-add-to : CFLAGS, CXXFLAGS, or FCFLAGS
+#    - $2 add-value-if-not-found : nothing
+#    - $3 action-if-found : add value to shellvariable
+#    - $4 action-if-not-found : nothing
+#
+#   NOTE: These macros depend on AX_APPEND_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2010 Rhys Ulerich <rhys.ulerich@gmail.com>
+#
+#   This program is free software; you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation; either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 16
+
+AC_DEFUN([AX_FLAGS_WARN_ALL],[dnl
+AS_VAR_PUSHDEF([FLAGS],[_AC_LANG_PREFIX[]FLAGS])dnl
+AS_VAR_PUSHDEF([VAR],[ac_cv_[]_AC_LANG_ABBREV[]flags_warn_all])dnl
+AC_CACHE_CHECK([m4_ifval($1,$1,FLAGS) for maximum warnings],
+VAR,[VAR="no, unknown"
+ac_save_[]FLAGS="$[]FLAGS"
+for ac_arg dnl
+in "-warn all  % -warn all"   dnl Intel
+   "-pedantic  % -Wall"       dnl GCC
+   "-xstrconst % -v"          dnl Solaris C
+   "-std1      % -verbose -w0 -warnprotos" dnl Digital Unix
+   "-qlanglvl=ansi % -qsrcmsg -qinfo=all:noppt:noppc:noobs:nocnd" dnl AIX
+   "-ansi -ansiE % -fullwarn" dnl IRIX
+   "+ESlit     % +w1"         dnl HP-UX C
+   "-Xc        % -pvctl[,]fullmsg" dnl NEC SX-5 (Super-UX 10)
+   "-h conform % -h msglevel 2" dnl Cray C (Unicos)
+   #
+do FLAGS="$ac_save_[]FLAGS "`echo $ac_arg | sed -e 's,%%.*,,' -e 's,%,,'`
+   AC_COMPILE_IFELSE([AC_LANG_PROGRAM],
+                     [VAR=`echo $ac_arg | sed -e 's,.*% *,,'` ; break])
+done
+FLAGS="$ac_save_[]FLAGS"
+])
+AS_VAR_POPDEF([FLAGS])dnl
+AX_REQUIRE_DEFINED([AX_APPEND_FLAG])
+case ".$VAR" in
+     .ok|.ok,*) m4_ifvaln($3,$3) ;;
+   .|.no|.no,*) m4_default($4,[m4_ifval($2,[AX_APPEND_FLAG([$2], [$1])])]) ;;
+   *) m4_default($3,[AX_APPEND_FLAG([$VAR], [$1])]) ;;
+esac
+AS_VAR_POPDEF([VAR])dnl
+])dnl AX_FLAGS_WARN_ALL
+dnl  implementation tactics:
+dnl   the for-argument contains a list of options. The first part of
+dnl   these does only exist to detect the compiler - usually it is
+dnl   a global option to enable -ansi or -extrawarnings. All other
+dnl   compilers will fail about it. That was needed since a lot of
+dnl   compilers will give false positives for some option-syntax
+dnl   like -Woption or -Xoption as they think of it is a pass-through
+dnl   to later compile stages or something. The "%" is used as a
+dnl   delimiter. A non-option comment can be given after "%%" marks
+dnl   which will be shown but not added to the respective C/CXXFLAGS.
+
+AC_DEFUN([AX_CFLAGS_WARN_ALL],[dnl
+AC_LANG_PUSH([C])
+AX_FLAGS_WARN_ALL([$1], [$2], [$3], [$4])
+AC_LANG_POP([C])
+])
+
+AC_DEFUN([AX_CXXFLAGS_WARN_ALL],[dnl
+AC_LANG_PUSH([C++])
+AX_FLAGS_WARN_ALL([$1], [$2], [$3], [$4])
+AC_LANG_POP([C++])
+])
+
+AC_DEFUN([AX_FCFLAGS_WARN_ALL],[dnl
+AC_LANG_PUSH([Fortran])
+AX_FLAGS_WARN_ALL([$1], [$2], [$3], [$4])
+AC_LANG_POP([Fortran])
+])
diff --git a/m4/ax_check_compile_flag.m4 b/m4/ax_check_compile_flag.m4
new file mode 100644
index 0000000..dcabb92
--- /dev/null
+++ b/m4/ax_check_compile_flag.m4
@@ -0,0 +1,74 @@
+# ===========================================================================
+#  https://www.gnu.org/software/autoconf-archive/ax_check_compile_flag.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_CHECK_COMPILE_FLAG(FLAG, [ACTION-SUCCESS], [ACTION-FAILURE], [EXTRA-FLAGS], [INPUT])
+#
+# DESCRIPTION
+#
+#   Check whether the given FLAG works with the current language's compiler
+#   or gives an error.  (Warnings, however, are ignored)
+#
+#   ACTION-SUCCESS/ACTION-FAILURE are shell commands to execute on
+#   success/failure.
+#
+#   If EXTRA-FLAGS is defined, it is added to the current language's default
+#   flags (e.g. CFLAGS) when the check is done.  The check is thus made with
+#   the flags: "CFLAGS EXTRA-FLAGS FLAG".  This can for example be used to
+#   force the compiler to issue an error when a bad flag is given.
+#
+#   INPUT gives an alternative input source to AC_COMPILE_IFELSE.
+#
+#   NOTE: Implementation based on AX_CFLAGS_GCC_OPTION. Please keep this
+#   macro in sync with AX_CHECK_{PREPROC,LINK}_FLAG.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Guido U. Draheim <guidod@gmx.de>
+#   Copyright (c) 2011 Maarten Bosmans <mkbosmans@gmail.com>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 5
+
+AC_DEFUN([AX_CHECK_COMPILE_FLAG],
+[AC_PREREQ(2.64)dnl for _AC_LANG_PREFIX and AS_VAR_IF
+AS_VAR_PUSHDEF([CACHEVAR],[ax_cv_check_[]_AC_LANG_ABBREV[]flags_$4_$1])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler accepts $1], CACHEVAR, [
+  ax_check_save_flags=$[]_AC_LANG_PREFIX[]FLAGS
+  _AC_LANG_PREFIX[]FLAGS="$[]_AC_LANG_PREFIX[]FLAGS $4 $1"
+  AC_COMPILE_IFELSE([m4_default([$5],[AC_LANG_PROGRAM()])],
+    [AS_VAR_SET(CACHEVAR,[yes])],
+    [AS_VAR_SET(CACHEVAR,[no])])
+  _AC_LANG_PREFIX[]FLAGS=$ax_check_save_flags])
+AS_VAR_IF(CACHEVAR,yes,
+  [m4_default([$2], :)],
+  [m4_default([$3], :)])
+AS_VAR_POPDEF([CACHEVAR])dnl
+])dnl AX_CHECK_COMPILE_FLAGS
diff --git a/m4/ax_require_defined.m4 b/m4/ax_require_defined.m4
new file mode 100644
index 0000000..17c3eab
--- /dev/null
+++ b/m4/ax_require_defined.m4
@@ -0,0 +1,37 @@
+# ===========================================================================
+#    https://www.gnu.org/software/autoconf-archive/ax_require_defined.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_REQUIRE_DEFINED(MACRO)
+#
+# DESCRIPTION
+#
+#   AX_REQUIRE_DEFINED is a simple helper for making sure other macros have
+#   been defined and thus are available for use.  This avoids random issues
+#   where a macro isn't expanded.  Instead the configure script emits a
+#   non-fatal:
+#
+#     ./configure: line 1673: AX_CFLAGS_WARN_ALL: command not found
+#
+#   It's like AC_REQUIRE except it doesn't expand the required macro.
+#
+#   Here's an example:
+#
+#     AX_REQUIRE_DEFINED([AX_CHECK_LINK_FLAG])
+#
+# LICENSE
+#
+#   Copyright (c) 2014 Mike Frysinger <vapier@gentoo.org>
+#
+#   Copying and distribution of this file, with or without modification, are
+#   permitted in any medium without royalty provided the copyright notice
+#   and this notice are preserved. This file is offered as-is, without any
+#   warranty.
+
+#serial 2
+
+AC_DEFUN([AX_REQUIRE_DEFINED], [dnl
+  m4_ifndef([$1], [m4_fatal([macro ]$1[ is not defined; is a m4 file missing?])])
+])dnl AX_REQUIRE_DEFINED
diff --git a/m4/gcc_version.m4 b/m4/gcc_version.m4
new file mode 100644
index 0000000..9e16450
--- /dev/null
+++ b/m4/gcc_version.m4
@@ -0,0 +1,38 @@
+dnl Copied from GNU Coreutils configure.ac
+dnl
+dnl The 17 lines are probably too trivial to be copyrightable, but just in case:
+dnl
+dnl Copyright (C) 1991-2017 Free Software Foundation, Inc.
+dnl
+dnl This program is free software: you can redistribute it and/or modify
+dnl it under the terms of the GNU General Public License as published by
+dnl the Free Software Foundation, either version 3 of the License, or
+dnl (at your option) any later version.
+dnl
+dnl This program is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+dnl GNU General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU General Public License
+dnl along with this program.  If not, see <https://www.gnu.org/licenses/>.
+dnl
+dnl Written by Jim Meyering.
+
+# gl_GCC_VERSION_IFELSE([major], [minor], [run-if-found], [run-if-not-found])
+# ------------------------------------------------
+# If $CPP is gcc-MAJOR.MINOR or newer, then run RUN-IF-FOUND.
+# Otherwise, run RUN-IF-NOT-FOUND.
+AC_DEFUN([gl_GCC_VERSION_IFELSE],
+  [AC_PREPROC_IFELSE(
+    [AC_LANG_PROGRAM(
+      [[
+#if ($1) < __GNUC__ || (($1) == __GNUC__ && ($2) <= __GNUC_MINOR__)
+/* ok */
+#else
+# error "your version of gcc is older than $1.$2"
+#endif
+      ]]),
+    ], [$3], [$4])
+  ]
+)
diff --git a/m4/gl_manywarnings.m4 b/m4/gl_manywarnings.m4
new file mode 100644
index 0000000..d10bcd0
--- /dev/null
+++ b/m4/gl_manywarnings.m4
@@ -0,0 +1,329 @@
+# manywarnings.m4 serial 13
+dnl Copyright (C) 2008-2017 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson
+
+# gl_MANYWARN_COMPLEMENT(OUTVAR, LISTVAR, REMOVEVAR)
+# --------------------------------------------------
+# Copy LISTVAR to OUTVAR except for the entries in REMOVEVAR.
+# Elements separated by whitespace.  In set logic terms, the function
+# does OUTVAR = LISTVAR \ REMOVEVAR.
+AC_DEFUN([gl_MANYWARN_COMPLEMENT],
+[
+  gl_warn_set=
+  set x $2; shift
+  for gl_warn_item
+  do
+    case " $3 " in
+      *" $gl_warn_item "*)
+        ;;
+      *)
+        gl_warn_set="$gl_warn_set $gl_warn_item"
+        ;;
+    esac
+  done
+  $1=$gl_warn_set
+])
+
+# gl_MANYWARN_ALL_GCC(VARIABLE)
+# -----------------------------
+# Add all documented GCC warning parameters to variable VARIABLE.
+# Note that you need to test them using gl_WARN_ADD if you want to
+# make sure your gcc understands it.
+#
+# The effects of this macro depend on the current language (_AC_LANG).
+AC_DEFUN([gl_MANYWARN_ALL_GCC],
+[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])
+
+# Specialization for _AC_LANG = C.
+# Use of m4_defun rather than AC_DEFUN works around a bug in autoconf < 2.63b.
+m4_defun([gl_MANYWARN_ALL_GCC(C)],
+[
+  AC_LANG_PUSH([C])
+
+  dnl First, check for some issues that only occur when combining multiple
+  dnl gcc warning categories.
+  AC_REQUIRE([AC_PROG_CC])
+  if test -n "$GCC"; then
+
+    dnl Check if -W -Werror -Wno-missing-field-initializers is supported
+    dnl with the current $CC $CFLAGS $CPPFLAGS.
+    AC_MSG_CHECKING([whether -Wno-missing-field-initializers is supported])
+    AC_CACHE_VAL([gl_cv_cc_nomfi_supported], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -W -Werror -Wno-missing-field-initializers"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_nomfi_supported=yes],
+        [gl_cv_cc_nomfi_supported=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_nomfi_supported])
+
+    if test "$gl_cv_cc_nomfi_supported" = yes; then
+      dnl Now check whether -Wno-missing-field-initializers is needed
+      dnl for the { 0, } construct.
+      AC_MSG_CHECKING([whether -Wno-missing-field-initializers is needed])
+      AC_CACHE_VAL([gl_cv_cc_nomfi_needed], [
+        gl_save_CFLAGS="$CFLAGS"
+        CFLAGS="$CFLAGS -W -Werror"
+        AC_COMPILE_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[int f (void)
+               {
+                 typedef struct { int a; int b; } s_t;
+                 s_t s1 = { 0, };
+                 return s1.b;
+               }
+             ]],
+             [[]])],
+          [gl_cv_cc_nomfi_needed=no],
+          [gl_cv_cc_nomfi_needed=yes])
+        CFLAGS="$gl_save_CFLAGS"
+      ])
+      AC_MSG_RESULT([$gl_cv_cc_nomfi_needed])
+    fi
+
+    dnl Next, check if -Werror -Wuninitialized is useful with the
+    dnl user's choice of $CFLAGS; some versions of gcc warn that it
+    dnl has no effect if -O is not also used
+    AC_MSG_CHECKING([whether -Wuninitialized is supported])
+    AC_CACHE_VAL([gl_cv_cc_uninitialized_supported], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -Werror -Wuninitialized"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_uninitialized_supported=yes],
+        [gl_cv_cc_uninitialized_supported=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_uninitialized_supported])
+
+  fi
+
+  # List all gcc warning categories.
+  # To compare this list to your installed GCC's, run this Bash command:
+  #
+  # comm -3 \
+  #  <(sed -n 's/^  *\(-[^ ]*\) .*/\1/p' manywarnings.m4 | sort) \
+  #  <(gcc --help=warnings | sed -n 's/^  \(-[^ ]*\) .*/\1/p' | sort |
+  #      grep -v -x -F -f <(
+  #         awk '/^[^#]/ {print $1}' ../build-aux/gcc-warning.spec))
+
+  gl_manywarn_set=
+  for gl_manywarn_item in -fno-common \
+    -W \
+    -Wabi \
+    -Waddress \
+    -Waggressive-loop-optimizations \
+    -Wall \
+    -Wattributes \
+    -Wbad-function-cast \
+    -Wbool-compare \
+    -Wbool-operation \
+    -Wbuiltin-declaration-mismatch \
+    -Wbuiltin-macro-redefined \
+    -Wcast-align \
+    -Wchar-subscripts \
+    -Wchkp \
+    -Wclobbered \
+    -Wcomment \
+    -Wcomments \
+    -Wcoverage-mismatch \
+    -Wcpp \
+    -Wdangling-else \
+    -Wdate-time \
+    -Wdeprecated \
+    -Wdeprecated-declarations \
+    -Wdesignated-init \
+    -Wdisabled-optimization \
+    -Wdiscarded-array-qualifiers \
+    -Wdiscarded-qualifiers \
+    -Wdiv-by-zero \
+    -Wdouble-promotion \
+    -Wduplicated-branches \
+    -Wduplicated-cond \
+    -Wduplicate-decl-specifier \
+    -Wempty-body \
+    -Wendif-labels \
+    -Wenum-compare \
+    -Wexpansion-to-defined \
+    -Wextra \
+    -Wformat-contains-nul \
+    -Wformat-extra-args \
+    -Wformat-nonliteral \
+    -Wformat-security \
+    -Wformat-signedness \
+    -Wformat-y2k \
+    -Wformat-zero-length \
+    -Wframe-address \
+    -Wfree-nonheap-object \
+    -Whsa \
+    -Wignored-attributes \
+    -Wignored-qualifiers \
+    -Wimplicit \
+    -Wimplicit-function-declaration \
+    -Wimplicit-int \
+    -Wincompatible-pointer-types \
+    -Winit-self \
+    -Winline \
+    -Wint-conversion \
+    -Wint-in-bool-context \
+    -Wint-to-pointer-cast \
+    -Winvalid-memory-model \
+    -Winvalid-pch \
+    -Wjump-misses-init \
+    -Wlogical-not-parentheses \
+    -Wlogical-op \
+    -Wmain \
+    -Wmaybe-uninitialized \
+    -Wmemset-elt-size \
+    -Wmemset-transposed-args \
+    -Wmisleading-indentation \
+    -Wmissing-braces \
+    -Wmissing-declarations \
+    -Wmissing-field-initializers \
+    -Wmissing-include-dirs \
+    -Wmissing-parameter-type \
+    -Wmissing-prototypes \
+    -Wmultichar \
+    -Wnarrowing \
+    -Wnested-externs \
+    -Wnonnull \
+    -Wnonnull-compare \
+    -Wnull-dereference \
+    -Wodr \
+    -Wold-style-declaration \
+    -Wold-style-definition \
+    -Wopenmp-simd \
+    -Woverflow \
+    -Woverlength-strings \
+    -Woverride-init \
+    -Wpacked \
+    -Wpacked-bitfield-compat \
+    -Wparentheses \
+    -Wpointer-arith \
+    -Wpointer-compare \
+    -Wpointer-sign \
+    -Wpointer-to-int-cast \
+    -Wpragmas \
+    -Wpsabi \
+    -Wrestrict \
+    -Wreturn-local-addr \
+    -Wreturn-type \
+    -Wscalar-storage-order \
+    -Wsequence-point \
+    -Wshadow \
+    -Wshift-count-negative \
+    -Wshift-count-overflow \
+    -Wshift-negative-value \
+    -Wsizeof-array-argument \
+    -Wsizeof-pointer-memaccess \
+    -Wstack-protector \
+    -Wstrict-aliasing \
+    -Wstrict-overflow \
+    -Wstrict-prototypes \
+    -Wsuggest-attribute=const \
+    -Wsuggest-attribute=format \
+    -Wsuggest-attribute=noreturn \
+    -Wsuggest-attribute=pure \
+    -Wsuggest-final-methods \
+    -Wsuggest-final-types \
+    -Wswitch \
+    -Wswitch-bool \
+    -Wswitch-default \
+    -Wswitch-unreachable \
+    -Wsync-nand \
+    -Wsystem-headers \
+    -Wtautological-compare \
+    -Wtrampolines \
+    -Wtrigraphs \
+    -Wtype-limits \
+    -Wuninitialized \
+    -Wunknown-pragmas \
+    -Wunsafe-loop-optimizations \
+    -Wunused \
+    -Wunused-but-set-parameter \
+    -Wunused-but-set-variable \
+    -Wunused-function \
+    -Wunused-label \
+    -Wunused-local-typedefs \
+    -Wunused-macros \
+    -Wunused-parameter \
+    -Wunused-result \
+    -Wunused-value \
+    -Wunused-variable \
+    -Wvarargs \
+    -Wvariadic-macros \
+    -Wvector-operation-performance \
+    -Wvla \
+    -Wvolatile-register-var \
+    -Wwrite-strings \
+    \
+    ; do
+    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
+  done
+
+  # gcc --help=warnings outputs an unusual form for these options; list
+  # them here so that the above 'comm' command doesn't report a false match.
+  # Would prefer "min (PTRDIFF_MAX, SIZE_MAX)", but it must be a literal.
+  # Also, AC_COMPUTE_INT requires it to fit in a long; it is 2**63 on
+  # the only platforms where it does not fit in a long, so make that
+  # a special case.
+  AC_MSG_CHECKING([max safe object size])
+  AC_COMPUTE_INT([gl_alloc_max],
+    [LONG_MAX < (PTRDIFF_MAX < (size_t) -1 ? PTRDIFF_MAX : (size_t) -1)
+     ? -1
+     : PTRDIFF_MAX < (size_t) -1 ? (long) PTRDIFF_MAX : (long) (size_t) -1],
+    [[#include <limits.h>
+      #include <stddef.h>
+      #include <stdint.h>
+    ]],
+    [gl_alloc_max=2147483647])
+  case $gl_alloc_max in
+    -1) gl_alloc_max=9223372036854775807;;
+  esac
+  AC_MSG_RESULT([$gl_alloc_max])
+  gl_manywarn_set="$gl_manywarn_set -Walloc-size-larger-than=$gl_alloc_max"
+  gl_manywarn_set="$gl_manywarn_set -Warray-bounds=2"
+  gl_manywarn_set="$gl_manywarn_set -Wformat-overflow=2"
+  gl_manywarn_set="$gl_manywarn_set -Wformat-truncation=2"
+  gl_manywarn_set="$gl_manywarn_set -Wimplicit-fallthrough=5"
+  gl_manywarn_set="$gl_manywarn_set -Wnormalized=nfc"
+  gl_manywarn_set="$gl_manywarn_set -Wshift-overflow=2"
+  gl_manywarn_set="$gl_manywarn_set -Wstringop-overflow=2"
+  gl_manywarn_set="$gl_manywarn_set -Wunused-const-variable=2"
+  gl_manywarn_set="$gl_manywarn_set -Wvla-larger-than=4031"
+
+  # These are needed for older GCC versions.
+  if test -n "$GCC"; then
+    case `($CC --version) 2>/dev/null` in
+      'gcc (GCC) '[[0-3]].* | \
+      'gcc (GCC) '4.[[0-7]].*)
+        gl_manywarn_set="$gl_manywarn_set -fdiagnostics-show-option"
+        gl_manywarn_set="$gl_manywarn_set -funit-at-a-time"
+          ;;
+    esac
+  fi
+
+  # Disable specific options as needed.
+  if test "$gl_cv_cc_nomfi_needed" = yes; then
+    gl_manywarn_set="$gl_manywarn_set -Wno-missing-field-initializers"
+  fi
+
+  if test "$gl_cv_cc_uninitialized_supported" = no; then
+    gl_manywarn_set="$gl_manywarn_set -Wno-uninitialized"
+  fi
+
+  $1=$gl_manywarn_set
+
+  AC_LANG_POP([C])
+])
+
+# Specialization for _AC_LANG = C++.
+# Use of m4_defun rather than AC_DEFUN works around a bug in autoconf < 2.63b.
+m4_defun([gl_MANYWARN_ALL_GCC(C++)],
+[
+  gl_MANYWARN_ALL_GCC_CXX_IMPL([$1])
+])
diff --git a/m4/gl_warnings.m4 b/m4/gl_warnings.m4
new file mode 100644
index 0000000..870472b
--- /dev/null
+++ b/m4/gl_warnings.m4
@@ -0,0 +1,106 @@
+# warnings.m4 serial 13
+dnl Copyright (C) 2008-2017 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson
+
+# gl_AS_VAR_APPEND(VAR, VALUE)
+# ----------------------------
+# Provide the functionality of AS_VAR_APPEND if Autoconf does not have it.
+m4_ifdef([AS_VAR_APPEND],
+[m4_copy([AS_VAR_APPEND], [gl_AS_VAR_APPEND])],
+[m4_define([gl_AS_VAR_APPEND],
+[AS_VAR_SET([$1], [AS_VAR_GET([$1])$2])])])
+
+
+# gl_COMPILER_OPTION_IF(OPTION, [IF-SUPPORTED], [IF-NOT-SUPPORTED],
+#                       [PROGRAM = AC_LANG_PROGRAM()])
+# -----------------------------------------------------------------
+# Check if the compiler supports OPTION when compiling PROGRAM.
+#
+# The effects of this macro depend on the current language (_AC_LANG).
+AC_DEFUN([gl_COMPILER_OPTION_IF],
+[
+dnl FIXME: gl_Warn must be used unquoted until we can assume Autoconf
+dnl 2.64 or newer.
+AS_VAR_PUSHDEF([gl_Warn], [gl_cv_warn_[]_AC_LANG_ABBREV[]_$1])dnl
+AS_VAR_PUSHDEF([gl_Flags], [_AC_LANG_PREFIX[]FLAGS])dnl
+AS_LITERAL_IF([$1],
+  [m4_pushdef([gl_Positive], m4_bpatsubst([$1], [^-Wno-], [-W]))],
+  [gl_positive="$1"
+case $gl_positive in
+  -Wno-*) gl_positive=-W`expr "X$gl_positive" : 'X-Wno-\(.*\)'` ;;
+esac
+m4_pushdef([gl_Positive], [$gl_positive])])dnl
+AC_CACHE_CHECK([whether _AC_LANG compiler handles $1], m4_defn([gl_Warn]), [
+  gl_save_compiler_FLAGS="$gl_Flags"
+  gl_AS_VAR_APPEND(m4_defn([gl_Flags]),
+    [" $gl_unknown_warnings_are_errors ]m4_defn([gl_Positive])["])
+  AC_LINK_IFELSE([m4_default([$4], [AC_LANG_PROGRAM([])])],
+                 [AS_VAR_SET(gl_Warn, [yes])],
+                 [AS_VAR_SET(gl_Warn, [no])])
+  gl_Flags="$gl_save_compiler_FLAGS"
+])
+AS_VAR_IF(gl_Warn, [yes], [$2], [$3])
+m4_popdef([gl_Positive])dnl
+AS_VAR_POPDEF([gl_Flags])dnl
+AS_VAR_POPDEF([gl_Warn])dnl
+])
+
+# gl_UNKNOWN_WARNINGS_ARE_ERRORS
+# ------------------------------
+# Clang doesn't complain about unknown warning options unless one also
+# specifies -Wunknown-warning-option -Werror.  Detect this.
+#
+# The effects of this macro depend on the current language (_AC_LANG).
+AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS],
+[_AC_LANG_DISPATCH([$0], _AC_LANG, $@)])
+
+# Specialization for _AC_LANG = C. This macro can be AC_REQUIREd.
+# Use of m4_defun rather than AC_DEFUN works around a bug in autoconf < 2.63b.
+m4_defun([gl_UNKNOWN_WARNINGS_ARE_ERRORS(C)],
+[
+  AC_LANG_PUSH([C])
+  gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL
+  AC_LANG_POP([C])
+])
+
+# Specialization for _AC_LANG = C++. This macro can be AC_REQUIREd.
+# Use of m4_defun rather than AC_DEFUN works around a bug in autoconf < 2.63b.
+m4_defun([gl_UNKNOWN_WARNINGS_ARE_ERRORS(C++)],
+[
+  AC_LANG_PUSH([C++])
+  gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL
+  AC_LANG_POP([C++])
+])
+
+AC_DEFUN([gl_UNKNOWN_WARNINGS_ARE_ERRORS_IMPL],
+[gl_COMPILER_OPTION_IF([-Werror -Wunknown-warning-option],
+   [gl_unknown_warnings_are_errors='-Wunknown-warning-option -Werror'],
+   [gl_unknown_warnings_are_errors=])])
+
+# gl_WARN_ADD(OPTION, [VARIABLE = WARN_CFLAGS/WARN_CXXFLAGS],
+#             [PROGRAM = AC_LANG_PROGRAM()])
+# -----------------------------------------------------------
+# Adds parameter to WARN_CFLAGS/WARN_CXXFLAGS if the compiler supports it
+# when compiling PROGRAM.  For example, gl_WARN_ADD([-Wparentheses]).
+#
+# If VARIABLE is a variable name, AC_SUBST it.
+#
+# The effects of this macro depend on the current language (_AC_LANG).
+AC_DEFUN([gl_WARN_ADD],
+[AC_REQUIRE([gl_UNKNOWN_WARNINGS_ARE_ERRORS(]_AC_LANG[)])
+gl_COMPILER_OPTION_IF([$1],
+  [gl_AS_VAR_APPEND(m4_if([$2], [], [[WARN_]_AC_LANG_PREFIX[FLAGS]], [[$2]]), [" $1"])],
+  [],
+  [$3])
+m4_ifval([$2],
+         [AS_LITERAL_IF([$2], [AC_SUBST([$2])])],
+         [AC_SUBST([WARN_]_AC_LANG_PREFIX[FLAGS])])dnl
+])
+
+# Local Variables:
+# mode: autoconf
+# End:
diff --git a/src/local.mk b/src/local.mk
new file mode 100644
index 0000000..51037fb
--- /dev/null
+++ b/src/local.mk
@@ -0,0 +1,2 @@
+@_SOURCES += \
+	%reldir%/main.c
diff --git a/src/main.c b/src/main.c
new file mode 100644
index 0000000..71f0d9b
--- /dev/null
+++ b/src/main.c
@@ -0,0 +1,5 @@
+int
+main(int argc, char *argv[])
+{
+	return 0;
+}