configure.ac - tmux - Rivoreo Source Code Repositories

 # configure.ac

 AC_INIT([tmux], 3.3-rc)
 AC_PREREQ([2.60])

 AC_CONFIG_AUX_DIR(etc)
 AC_CONFIG_LIBOBJ_DIR(compat)
 AM_INIT_AUTOMAKE([foreign subdir-objects])

 AC_CANONICAL_HOST

 # When CFLAGS isn't set at this stage and gcc is detected by the macro below,
 # autoconf will automatically use CFLAGS="-O2 -g". Prevent that by using an
 # empty default.
 : ${CFLAGS=""}

 # Save user CPPFLAGS, CFLAGS and LDFLAGS. We need to change them because
 # AC_CHECK_HEADER doesn't give us any other way to update the include
 # paths. But for Makefile.am we want to use AM_CPPFLAGS and friends.
 SAVED_CFLAGS="$CFLAGS"
 SAVED_CPPFLAGS="$CPPFLAGS"
 SAVED_LDFLAGS="$LDFLAGS"

 # Is this oss-fuzz build?
 AC_ARG_ENABLE(
 	fuzzing,
 	AS_HELP_STRING(--enable-fuzzing, build fuzzers)
 )
 AC_ARG_VAR(
 	FUZZING_LIBS,
 	AS_HELP_STRING(libraries to link fuzzing targets with)
 )

 # Set up convenient fuzzing defaults before initializing compiler.
 if test "x$enable_fuzzing" = xyes; then
 	AC_DEFINE(NEED_FUZZING)
 	test "x$CC" = x && CC=clang
 	test "x$FUZZING_LIBS" = x && \
 		FUZZING_LIBS="-fsanitize=fuzzer"
 	test "x$SAVED_CFLAGS" = x && \
 		AM_CFLAGS="-g -fsanitize=fuzzer-no-link,address"
 fi

 # Set up the compiler in two different ways and say yes we may want to install.
 AC_PROG_CC
 AM_PROG_CC_C_O
 AC_PROG_CC_C99
 AC_PROG_CPP
 AC_PROG_EGREP
 AC_PROG_INSTALL
 AC_PROG_YACC
 PKG_PROG_PKG_CONFIG
 AC_USE_SYSTEM_EXTENSIONS

 # Default tmux.conf goes in /etc not ${prefix}/etc.
 test "$sysconfdir" = '${prefix}/etc' && sysconfdir=/etc

 # Is this --enable-debug?
 case "x$VERSION" in xnext*) enable_debug=yes;; esac
 AC_ARG_ENABLE(
 	debug,
 	AS_HELP_STRING(--enable-debug, enable debug build flags),
 )
 AM_CONDITIONAL(IS_DEBUG, test "x$enable_debug" = xyes)

 # Is this a static build?
 AC_ARG_ENABLE(
 	static,
 	AS_HELP_STRING(--enable-static, create a static build)
 )
 if test "x$enable_static" = xyes; then
 	test "x$PKG_CONFIG" != x && PKG_CONFIG="$PKG_CONFIG --static"
 	AM_LDFLAGS="-static $AM_LDFLAGS"
 	LDFLAGS="$AM_LDFLAGS $SAVED_LDFLAGS"
 fi

 # Allow default TERM to be set.
 AC_ARG_WITH(
 	TERM,
 	AS_HELP_STRING(--with-TERM, set default TERM),
 	[DEFAULT_TERM=$withval],
 	[DEFAULT_TERM=]
 )
 case "x$DEFAULT_TERM" in
 	xscreen*|xtmux*|x)
 	;;
 	*)
 		AC_MSG_ERROR("unsuitable TERM (must be screen* or tmux*)")
 	;;
 esac

 # Do we need fuzzers?
 AM_CONDITIONAL(NEED_FUZZING, test "x$enable_fuzzing" = xyes)

 # Is this gcc?
 AM_CONDITIONAL(IS_GCC, test "x$GCC" = xyes -a "x$enable_fuzzing" != xyes)

 # Is this Sun CC?
 AC_EGREP_CPP(
 	yes,
 	[
 		#ifdef __SUNPRO_C
 		yes
 		#endif
 	],
 	found_suncc=yes,
 	found_suncc=no
 )
 AM_CONDITIONAL(IS_SUNCC, test "x$found_suncc" = xyes)

 # Check for various headers. Alternatives included from compat.h.
 AC_CHECK_HEADERS([ \
 	bitstring.h \
 	dirent.h \
 	fcntl.h \
 	inttypes.h \
 	libproc.h \
 	libutil.h \
 	ndir.h \
 	paths.h \
 	pty.h \
 	stdint.h \
 	sys/dir.h \
 	sys/ndir.h \
 	sys/tree.h \
 	util.h \
 ])

 # Look for sys_signame.
 AC_SEARCH_LIBS(sys_signame, , AC_DEFINE(HAVE_SYS_SIGNAME))

 # Look for fmod.
 AC_CHECK_LIB(m, fmod)

 # Look for library needed for flock.
 AC_SEARCH_LIBS(flock, bsd)

 # Check for functions that are replaced or omitted.
 AC_CHECK_FUNCS([ \
 	dirfd \
 	flock \
 	prctl \
 	proc_pidinfo \
 	sysconf
 ])

 # Check for functions with a compatibility implementation.
 AC_REPLACE_FUNCS([ \
 	asprintf \
 	cfmakeraw \
 	clock_gettime \
 	closefrom \
 	explicit_bzero \
 	fgetln \
 	freezero \
 	getdtablecount \
 	getdtablesize \
 	getline \
 	getprogname \
 	memmem \
 	setenv \
 	setproctitle \
 	strcasestr \
 	strlcat \
 	strlcpy \
 	strndup \
 	strsep \
 ])
 AC_FUNC_STRNLEN

 # Check if strtonum works.
 AC_MSG_CHECKING([for working strtonum])
 AC_RUN_IFELSE([AC_LANG_PROGRAM(
 		[#include <stdlib.h>],
 		[return (strtonum("0", 0, 1, NULL) == 0 ? 0 : 1);]
 	)],
 	[AC_DEFINE(HAVE_STRTONUM) AC_MSG_RESULT(yes)],
 	[AC_LIBOBJ(strtonum) AC_MSG_RESULT(no)],
 	[AC_LIBOBJ(strtonum) AC_MSG_RESULT(no)]
 )

 # Clang sanitizers wrap reallocarray even if it isn't available on the target
 # system. When compiled it always returns NULL and crashes the program. To
 # detect this we need a more complicated test.
 AC_MSG_CHECKING([for working reallocarray])
 AC_RUN_IFELSE([AC_LANG_PROGRAM(
 		[#include <stdlib.h>],
 		[return (reallocarray(NULL, 1, 1) == NULL);]
 	)],
 	AC_MSG_RESULT(yes),
 	[AC_LIBOBJ(reallocarray) AC_MSG_RESULT([no])],
 	[AC_LIBOBJ(reallocarray) AC_MSG_RESULT([no])]
 )
 AC_MSG_CHECKING([for working recallocarray])
 AC_RUN_IFELSE([AC_LANG_PROGRAM(
 		[#include <stdlib.h>],
 		[return (recallocarray(NULL, 1, 1, 1) == NULL);]
 	)],
 	AC_MSG_RESULT(yes),
 	[AC_LIBOBJ(recallocarray) AC_MSG_RESULT([no])],
 	[AC_LIBOBJ(recallocarray) AC_MSG_RESULT([no])]
 )

 # Look for clock_gettime. Must come before event_init.
 AC_SEARCH_LIBS(clock_gettime, rt)

 # Always use our getopt because 1) glibc's doesn't enforce argument order 2)
 # musl does not set optarg to NULL for flags without arguments (although it is
 # not required to, but it is helpful) 3) there are probably other weird
 # implementations.
 AC_LIBOBJ(getopt)

 # Look for libevent. Try libevent_core or libevent with pkg-config first then
 # look for the library.
 PKG_CHECK_MODULES(
 	LIBEVENT_CORE,
 	[libevent_core >= 2],
 	[
 		AM_CPPFLAGS="$LIBEVENT_CORE_CFLAGS $AM_CPPFLAGS"
 		CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
 		LIBS="$LIBEVENT_CORE_LIBS $LIBS"
 		found_libevent=yes
 	],
 	found_libevent=no
 )
 if test x$found_libevent = xno; then
 	PKG_CHECK_MODULES(
 		LIBEVENT,
 		[libevent >= 2],
 		[
 			AM_CPPFLAGS="$LIBEVENT_CFLAGS $AM_CPPFLAGS"
 			CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBEVENT_LIBS $LIBS"
 			found_libevent=yes
 		],
 		found_libevent=no
 	)
 fi
 if test x$found_libevent = xno; then
 	AC_SEARCH_LIBS(
 		event_init,
 		[event_core event event-1.4],
 		found_libevent=yes,
 		found_libevent=no
 	)
 fi
 AC_CHECK_HEADER(
 	event2/event.h,
 	AC_DEFINE(HAVE_EVENT2_EVENT_H),
 	[
 		AC_CHECK_HEADER(
 			event.h,
 			AC_DEFINE(HAVE_EVENT_H),
 			found_libevent=no
 		)
 	]
 )
 if test "x$found_libevent" = xno; then
 	AC_MSG_ERROR("libevent not found")
 fi

 # Look for ncurses or curses. Try pkg-config first then directly for the
 # library.
 PKG_CHECK_MODULES(
 	LIBTINFO,
 	tinfo,
 	[
 		AM_CPPFLAGS="$LIBTINFO_CFLAGS $AM_CPPFLAGS"
 		CPPFLAGS="$LIBTINFO_CFLAGS $SAVED_CPPFLAGS"
 		LIBS="$LIBTINFO_LIBS $LIBS"
 		found_ncurses=yes
 	],
 	found_ncurses=no
 )
 if test "x$found_ncurses" = xno; then
 	PKG_CHECK_MODULES(
 		LIBNCURSES,
 		ncurses,
 		[
 			AM_CPPFLAGS="$LIBNCURSES_CFLAGS $AM_CPPFLAGS"
 			CPPFLAGS="$LIBNCURSES_CFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBNCURSES_LIBS $LIBS"
 			found_ncurses=yes
 		],
 		found_ncurses=no
 	)
 fi
 if test "x$found_ncurses" = xno; then
 	PKG_CHECK_MODULES(
 		LIBNCURSESW,
 		ncursesw,
 		[
 			AM_CPPFLAGS="$LIBNCURSESW_CFLAGS $AM_CPPFLAGS"
 			CPPFLAGS="$LIBNCURSESW_CFLAGS $SAVED_CPPFLAGS"
 			LIBS="$LIBNCURSESW_LIBS $LIBS"
 			found_ncurses=yes
 		],
 		found_ncurses=no
 	)
 fi
 if test "x$found_ncurses" = xno; then
 	AC_SEARCH_LIBS(
 		setupterm,
 		[tinfo ncurses ncursesw],
 		found_ncurses=yes,
 		found_ncurses=no
 	)
 	if test "x$found_ncurses" = xyes; then
 		AC_CHECK_HEADER(
 			ncurses.h,
 			LIBS="$LIBS -lncurses",
 			found_ncurses=no
 		)
 	fi
 fi
 if test "x$found_ncurses" = xyes; then
 	CPPFLAGS="$CPPFLAGS -DHAVE_NCURSES_H"
 	AC_DEFINE(HAVE_NCURSES_H)
 else
 	AC_CHECK_LIB(
 		curses,
 		setupterm,
 		found_curses=yes,
 		found_curses=no
 	)
 	AC_CHECK_HEADER(
 		curses.h,
 		,
 		found_curses=no
 	)
 	if test "x$found_curses" = xyes; then
 		LIBS="$LIBS -lcurses"
 		CPPFLAGS="$CPPFLAGS -DHAVE_CURSES_H"
 		AC_DEFINE(HAVE_CURSES_H)
 	else
 		AC_MSG_ERROR("curses not found")
 	fi
 fi

 # Look for utempter.
 AC_ARG_ENABLE(
 	utempter,
 	AS_HELP_STRING(--enable-utempter, use utempter if it is installed)
 )
 if test "x$enable_utempter" = xyes; then
 	AC_CHECK_HEADER(utempter.h, enable_utempter=yes, enable_utempter=no)
 	if test "x$enable_utempter" = xyes; then
 		AC_SEARCH_LIBS(
 			utempter_add_record,
 			utempter,
 			enable_utempter=yes,
 			enable_utempter=no
 		)
 	fi
 	if test "x$enable_utempter" = xyes; then
 		AC_DEFINE(HAVE_UTEMPTER)
 	else
 		AC_MSG_ERROR("utempter not found")
 	fi
 fi

 # Look for utf8proc.
 AC_ARG_ENABLE(
 	utf8proc,
 	AS_HELP_STRING(--enable-utf8proc, use utf8proc if it is installed)
 )
 if test "x$enable_utf8proc" = xyes; then
 	AC_CHECK_HEADER(utf8proc.h, enable_utf8proc=yes, enable_utf8proc=no)
 	if test "x$enable_utf8proc" = xyes; then
 		AC_SEARCH_LIBS(
 			utf8proc_charwidth,
 			utf8proc,
 			enable_utf8proc=yes,
 			enable_utf8proc=no
 		)
 	fi
 	if test "x$enable_utf8proc" = xyes; then
 		AC_DEFINE(HAVE_UTF8PROC)
 	else
 		AC_MSG_ERROR("utf8proc not found")
 	fi
 fi
 AM_CONDITIONAL(HAVE_UTF8PROC, [test "x$enable_utf8proc" = xyes])

 # Check for b64_ntop. If we have b64_ntop, we assume b64_pton as well.
 AC_MSG_CHECKING(for b64_ntop)
 	AC_LINK_IFELSE([AC_LANG_PROGRAM(
 	[
 		#include <sys/types.h>
 		#include <netinet/in.h>
 		#include <resolv.h>
 	],
 	[
 		b64_ntop(NULL, 0, NULL, 0);
 	])],
 	found_b64_ntop=yes,
 	found_b64_ntop=no
 )
 AC_MSG_RESULT($found_b64_ntop)
 OLD_LIBS="$LIBS"
 if test "x$found_b64_ntop" = xno; then
 	AC_MSG_CHECKING(for b64_ntop with -lresolv)
 	LIBS="$OLD_LIBS -lresolv"
 	AC_LINK_IFELSE([AC_LANG_PROGRAM(
 		[
 			#include <sys/types.h>
 			#include <netinet/in.h>
 			#include <resolv.h>
 		],
 		[
 			b64_ntop(NULL, 0, NULL, 0);
 		])],
 		found_b64_ntop=yes,
 		found_b64_ntop=no
 	)
 	AC_MSG_RESULT($found_b64_ntop)
 fi
 if test "x$found_b64_ntop" = xno; then
 	AC_MSG_CHECKING(for b64_ntop with -lnetwork)
 	LIBS="$OLD_LIBS -lnetwork"
 	AC_LINK_IFELSE([AC_LANG_PROGRAM(
 		[
 			#include <sys/types.h>
 			#include <netinet/in.h>
 			#include <resolv.h>
 		],
 		[
 			b64_ntop(NULL, 0, NULL, 0);
 		])],
 		found_b64_ntop=yes,
 		found_b64_ntop=no
 	)
 	AC_MSG_RESULT($found_b64_ntop)
 fi
 if test "x$found_b64_ntop" = xyes; then
 	AC_DEFINE(HAVE_B64_NTOP)
 else
 	LIBS="$OLD_LIBS"
 	AC_LIBOBJ(base64)
 fi

 # Look for networking libraries.
 AC_SEARCH_LIBS(inet_ntoa, nsl)
 AC_SEARCH_LIBS(socket, socket)
 AC_CHECK_LIB(xnet, socket)

 # Check if using glibc and have malloc_trim(3). The glibc free(3) is pretty bad
 # about returning memory to the kernel unless the application tells it when to
 # with malloc_trim(3).
 AC_MSG_CHECKING(if free doesn't work very well)
 AC_LINK_IFELSE([AC_LANG_SOURCE(
 	[
 		#include <stdlib.h>
 		#ifdef __GLIBC__
 		#include <malloc.h>
 		int main(void) {
 			malloc_trim (0);
 			exit(0);
 		}
 		#else
 		no
 		#endif
 	])],
 	found_malloc_trim=yes,
 	found_malloc_trim=no
 )
 AC_MSG_RESULT($found_malloc_trim)
 if test "x$found_malloc_trim" = xyes; then
 	AC_DEFINE(HAVE_MALLOC_TRIM)
 fi

 # Check for CMSG_DATA. On some platforms like HP-UX this requires UNIX 95
 # (_XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED) (see xopen_networking(7)). On
 # others, UNIX 03 (_XOPEN_SOURCE 600, see standards(7) on Solaris).
 XOPEN_DEFINES=
 AC_MSG_CHECKING(for CMSG_DATA)
 AC_EGREP_CPP(
 	yes,
 	[
 		#include <sys/socket.h>
 		#ifdef CMSG_DATA
 		yes
 		#endif
 	],
 	found_cmsg_data=yes,
 	found_cmsg_data=no
 )
 AC_MSG_RESULT($found_cmsg_data)
 if test "x$found_cmsg_data" = xno; then
 	AC_MSG_CHECKING(if CMSG_DATA needs _XOPEN_SOURCE_EXTENDED)
 	AC_EGREP_CPP(
 		yes,
 		[
 			#define _XOPEN_SOURCE 1
 			#define _XOPEN_SOURCE_EXTENDED 1
 			#include <sys/socket.h>
 			#ifdef CMSG_DATA
 			yes
 			#endif
 		],
 		found_cmsg_data=yes,
 		found_cmsg_data=no
 	)
 	AC_MSG_RESULT($found_cmsg_data)
 	if test "x$found_cmsg_data" = xyes; then
 		XOPEN_DEFINES="-D_XOPEN_SOURCE -D_XOPEN_SOURCE_EXTENDED"
 	fi
 fi
 if test "x$found_cmsg_data" = xno; then
 	AC_MSG_CHECKING(if CMSG_DATA needs _XOPEN_SOURCE 600)
 	AC_EGREP_CPP(
 		yes,
 		[
 			#define _XOPEN_SOURCE 600
 			#include <sys/socket.h>
 			#ifdef CMSG_DATA
 			yes
 			#endif
 		],
 		found_cmsg_data=yes,
 		found_cmsg_data=no
 	)
 	AC_MSG_RESULT($found_cmsg_data)
 	if test "x$found_cmsg_data" = xyes; then
 		XOPEN_DEFINES="-D_XOPEN_SOURCE=600"
 	else
 		AC_MSG_ERROR("CMSG_DATA not found")
 	fi
 fi
 AC_SUBST(XOPEN_DEFINES)

 # Look for err and friends in err.h.
 AC_CHECK_FUNC(err, found_err_h=yes, found_err_h=no)
 AC_CHECK_FUNC(errx, , found_err_h=no)
 AC_CHECK_FUNC(warn, , found_err_h=no)
 AC_CHECK_FUNC(warnx, , found_err_h=no)
 if test "x$found_err_h" = xyes; then
 	AC_CHECK_HEADER(err.h, , found_err_h=no)
 else
 	AC_LIBOBJ(err)
 fi

 # Look for imsg_init in libutil.
 AC_SEARCH_LIBS(imsg_init, util, found_imsg_init=yes, found_imsg_init=no)
 if test "x$found_imsg_init" = xyes; then
 	AC_DEFINE(HAVE_IMSG)
 else
 	AC_LIBOBJ(imsg)
 	AC_LIBOBJ(imsg-buffer)
 fi

 # Look for daemon, compat/daemon.c used if missing. Solaris 10 has it in
 # libresolv, but no declaration anywhere, so check for declaration as well as
 # function.
 AC_CHECK_FUNC(daemon, found_daemon=yes, found_daemon=no)
 AC_CHECK_DECL(
 	daemon,
 	,
 	found_daemon=no,
 	[
 		#include <stdlib.h>
 		#include <unistd.h>
 	]
 )
 if test "x$found_daemon" = xyes; then
 	AC_DEFINE(HAVE_DAEMON)
 else
 	AC_LIBOBJ(daemon)
 fi

 # Look for stravis, compat/{vis,unvis}.c used if missing.
 AC_CHECK_FUNC(stravis, found_stravis=yes, found_stravis=no)
 if test "x$found_stravis" = xyes; then
 	AC_MSG_CHECKING(if strnvis is broken)
 	AC_EGREP_HEADER([strnvis\(char \*, const char \*, size_t, int\)],
 			vis.h,
 			AC_MSG_RESULT(no),
 			[found_stravis=no])
 	if test "x$found_stravis" = xno; then
 		AC_MSG_RESULT(yes)
 	fi
 fi
 if test "x$found_stravis" = xyes; then
 	AC_CHECK_DECL(
 		VIS_DQ,
 		,
 		found_stravis=no,
 		[
 			#include <stdlib.h>
 			#include <vis.h>
 		]
 )
 fi
 if test "x$found_stravis" = xyes; then
 	AC_DEFINE(HAVE_VIS)
 else
 	AC_LIBOBJ(vis)
 	AC_LIBOBJ(unvis)
 fi

 # Look for fdforkpty and forkpty in libutil.
 AC_SEARCH_LIBS(fdforkpty, util, found_fdforkpty=yes, found_fdforkpty=no)
 if test "x$found_fdforkpty" = xyes; then
 	AC_DEFINE(HAVE_FDFORKPTY)
 else
 	AC_LIBOBJ(fdforkpty)
 fi
 AC_SEARCH_LIBS(forkpty, util, found_forkpty=yes, found_forkpty=no)
 if test "x$found_forkpty" = xyes; then
 	AC_DEFINE(HAVE_FORKPTY)
 fi
 AM_CONDITIONAL(NEED_FORKPTY, test "x$found_forkpty" = xno)

 # Look for kinfo_getfile in libutil.
 AC_SEARCH_LIBS(kinfo_getfile, [util util-freebsd])

 # Look for a suitable queue.h.
 AC_CHECK_DECL(
 	TAILQ_CONCAT,
 	found_queue_h=yes,
 	found_queue_h=no,
 	[#include <sys/queue.h>]
 )
 AC_CHECK_DECL(
 	TAILQ_PREV,
 	,
 	found_queue_h=no,
 	[#include <sys/queue.h>]
 )
 AC_CHECK_DECL(
 	TAILQ_REPLACE,
 	,
 	found_queue_h=no,
 	[#include <sys/queue.h>]
 )
 if test "x$found_queue_h" = xyes; then
 	AC_DEFINE(HAVE_QUEUE_H)
 fi

 # Look for __progname.
 AC_MSG_CHECKING(for __progname)
 AC_LINK_IFELSE([AC_LANG_SOURCE(
 	[
 		#include <stdio.h>
 		#include <stdlib.h>
 		extern char *__progname;
 		int main(void) {
 			const char *cp = __progname;
 			printf("%s\n", cp);
 			exit(0);
 		}
 	])],
 	[AC_DEFINE(HAVE___PROGNAME) AC_MSG_RESULT(yes)],
 	AC_MSG_RESULT(no)
 )

 # Look for program_invocation_short_name.
 AC_MSG_CHECKING(for program_invocation_short_name)
 AC_LINK_IFELSE([AC_LANG_SOURCE(
 	[
 		#include <errno.h>
 		#include <stdio.h>
 		#include <stdlib.h>
 		int main(void) {
 			const char *cp = program_invocation_short_name;
 			printf("%s\n", cp);
 			exit(0);
 		}
 	])],
 	[AC_DEFINE(HAVE_PROGRAM_INVOCATION_SHORT_NAME) AC_MSG_RESULT(yes)],
 	AC_MSG_RESULT(no)
 )

 # Look for prctl(PR_SET_NAME).
 AC_CHECK_DECL(
 	PR_SET_NAME,
 	AC_DEFINE(HAVE_PR_SET_NAME),
 	,
 	[#include <sys/prctl.h>]
 )

 # Look for fcntl(F_CLOSEM).
 AC_CHECK_DECL(
 	F_CLOSEM,
 	AC_DEFINE(HAVE_FCNTL_CLOSEM),
 	,
 	[#include <fcntl.h>]
 )

 # Look for /proc/$$.
 AC_MSG_CHECKING(for /proc/\$\$)
 if test -d /proc/$$; then
 	AC_DEFINE(HAVE_PROC_PID)
 	AC_MSG_RESULT(yes)
 else
 	AC_MSG_RESULT(no)
 fi

 # Try to figure out what the best value for TERM might be.
 if test "x$DEFAULT_TERM" = x; then
 	DEFAULT_TERM=screen
 	AC_MSG_CHECKING(TERM)
 	AC_RUN_IFELSE([AC_LANG_SOURCE(
 		[
 			#include <stdio.h>
 			#include <stdlib.h>
 			#if defined(HAVE_CURSES_H)
 			#include <curses.h>
 			#elif defined(HAVE_NCURSES_H)
 			#include <ncurses.h>
 			#endif
 			#include <term.h>
 			int main(void) {
 				if (setupterm("screen-256color", -1, NULL) != OK)
 					exit(1);
 				exit(0);
 			}
 		 ])],
 		 [DEFAULT_TERM=screen-256color],
 		 ,
 		 [DEFAULT_TERM=screen]
 	)
 	AC_RUN_IFELSE([AC_LANG_SOURCE(
 		[
 			#include <stdio.h>
 			#include <stdlib.h>
 			#if defined(HAVE_CURSES_H)
 			#include <curses.h>
 			#elif defined(HAVE_NCURSES_H)
 			#include <ncurses.h>
 			#endif
 			#include <term.h>
 			int main(void) {
 				if (setupterm("tmux", -1, NULL) != OK)
 					exit(1);
 				exit(0);
 			}
 		 ])],
 		 [DEFAULT_TERM=tmux],
 		 ,
 		 [DEFAULT_TERM=screen]
 	)
 	AC_RUN_IFELSE([AC_LANG_SOURCE(
 		[
 			#include <stdio.h>
 			#include <stdlib.h>
 			#if defined(HAVE_CURSES_H)
 			#include <curses.h>
 			#elif defined(HAVE_NCURSES_H)
 			#include <ncurses.h>
 			#endif
 			#include <term.h>
 			int main(void) {
 				if (setupterm("tmux-256color", -1, NULL) != OK)
 					exit(1);
 				exit(0);
 			}
 		 ])],
 		 [DEFAULT_TERM=tmux-256color],
 		 ,
 		 [DEFAULT_TERM=screen]
 	)
 	AC_MSG_RESULT($DEFAULT_TERM)
 fi
 AC_SUBST(DEFAULT_TERM)

 # Man page defaults to mdoc.
 MANFORMAT=mdoc
 AC_SUBST(MANFORMAT)

 # Figure out the platform.
 AC_MSG_CHECKING(platform)
 case "$host_os" in
 	*aix*)
 		AC_MSG_RESULT(aix)
 		PLATFORM=aix
 		;;
 	*darwin*)
 		AC_MSG_RESULT(darwin)
 		PLATFORM=darwin
 		#
 		# macOS uses __dead2 instead of __dead, like FreeBSD. But it defines
 		# __dead away so it needs to be removed before we can replace it.
 		#
 		AC_DEFINE(BROKEN___DEAD)
 		#
 		# macOS CMSG_FIRSTHDR is broken, so redefine it with a working one.
 		# daemon works but has some stupid side effects, so use our internal
 		# version which has a workaround.
 		#
 		AC_DEFINE(BROKEN_CMSG_FIRSTHDR)
 		AC_LIBOBJ(daemon)
 		AC_LIBOBJ(daemon-darwin)
 		#
 		# macOS wcwidth(3) is bad, so complain and suggest using utf8proc
 		# instead.
 		#
 		if test "x$enable_utf8proc" = x; then
 			AC_MSG_NOTICE([])
 			AC_MSG_NOTICE([	   macOS library support for Unicode is very poor,])
 			AC_MSG_NOTICE([	   particularly for complex codepoints like emojis;])
 			AC_MSG_NOTICE([	   to use these correctly, configuring with])
 			AC_MSG_NOTICE([	   --enable-utf8proc is recommended. To build])
 			AC_MSG_NOTICE([	   without anyway, use --disable-utf8proc])
 			AC_MSG_NOTICE([])
 			AC_MSG_ERROR([must give --enable-utf8proc or --disable-utf8proc])
 		fi
 		;;
 	*dragonfly*)
 		AC_MSG_RESULT(dragonfly)
 		PLATFORM=dragonfly
 		;;
 	*linux*)
 		AC_MSG_RESULT(linux)
 		PLATFORM=linux
 		;;
 	*freebsd*)
 		AC_MSG_RESULT(freebsd)
 		PLATFORM=freebsd
 		;;
 	*netbsd*)
 		AC_MSG_RESULT(netbsd)
 		PLATFORM=netbsd
 		;;
 	*openbsd*)
 		AC_MSG_RESULT(openbsd)
 		PLATFORM=openbsd
 		;;
 	*sunos*)
 		AC_MSG_RESULT(sunos)
 		PLATFORM=sunos
 		;;
 	*solaris*)
 		AC_MSG_RESULT(sunos)
 		PLATFORM=sunos
 		case `/usr/bin/nroff --version 2>&1` in
 			*GNU*)
 				# Solaris 11.4 and later use GNU groff.
 				MANFORMAT=mdoc
 				;;
 			*)
 				# Solaris 2.0 to 11.3 use AT&T nroff.
 				MANFORMAT=man
 				;;
 		esac
 		;;
 	*hpux*)
 		AC_MSG_RESULT(hpux)
 		PLATFORM=hpux
 		;;
 	*cygwin*|*msys*)
 		AC_MSG_RESULT(cygwin)
 		PLATFORM=cygwin
 		;;
 	*haiku*)
 		AC_MSG_RESULT(haiku)
 		PLATFORM=haiku
 		;;
 	*)
 		AC_MSG_RESULT(unknown)
 		PLATFORM=unknown
 		;;
 esac
 AC_SUBST(PLATFORM)
 AM_CONDITIONAL(IS_AIX, test "x$PLATFORM" = xaix)
 AM_CONDITIONAL(IS_DARWIN, test "x$PLATFORM" = xdarwin)
 AM_CONDITIONAL(IS_DRAGONFLY, test "x$PLATFORM" = xdragonfly)
 AM_CONDITIONAL(IS_LINUX, test "x$PLATFORM" = xlinux)
 AM_CONDITIONAL(IS_FREEBSD, test "x$PLATFORM" = xfreebsd)
 AM_CONDITIONAL(IS_NETBSD, test "x$PLATFORM" = xnetbsd)
 AM_CONDITIONAL(IS_OPENBSD, test "x$PLATFORM" = xopenbsd)
 AM_CONDITIONAL(IS_SUNOS, test "x$PLATFORM" = xsunos)
 AM_CONDITIONAL(IS_HPUX, test "x$PLATFORM" = xhpux)
 AM_CONDITIONAL(IS_HAIKU, test "x$PLATFORM" = xhaiku)
 AM_CONDITIONAL(IS_UNKNOWN, test "x$PLATFORM" = xunknown)

 # Save our CFLAGS/CPPFLAGS/LDFLAGS for the Makefile and restore the old user
 # variables.
 AC_SUBST(AM_CPPFLAGS)
 CPPFLAGS="$SAVED_CPPFLAGS"
 AC_SUBST(AM_CFLAGS)
 CFLAGS="$SAVED_CFLAGS"
 AC_SUBST(AM_LDFLAGS)
 LDFLAGS="$SAVED_LDFLAGS"

 # autoconf should create a Makefile.
 AC_CONFIG_FILES(Makefile)
 AC_OUTPUT
	# configure.ac

	AC_INIT([tmux], 3.3-rc)
	AC_PREREQ([2.60])

	AC_CONFIG_AUX_DIR(etc)
	AC_CONFIG_LIBOBJ_DIR(compat)
	AM_INIT_AUTOMAKE([foreign subdir-objects])

	AC_CANONICAL_HOST

	# When CFLAGS isn't set at this stage and gcc is detected by the macro below,
	# autoconf will automatically use CFLAGS="-O2 -g". Prevent that by using an
	# empty default.
	: ${CFLAGS=""}

	# Save user CPPFLAGS, CFLAGS and LDFLAGS. We need to change them because
	# AC_CHECK_HEADER doesn't give us any other way to update the include
	# paths. But for Makefile.am we want to use AM_CPPFLAGS and friends.
	SAVED_CFLAGS="$CFLAGS"
	SAVED_CPPFLAGS="$CPPFLAGS"
	SAVED_LDFLAGS="$LDFLAGS"

	# Is this oss-fuzz build?
	AC_ARG_ENABLE(
	fuzzing,
	AS_HELP_STRING(--enable-fuzzing, build fuzzers)
	)
	AC_ARG_VAR(
	FUZZING_LIBS,
	AS_HELP_STRING(libraries to link fuzzing targets with)
	)

	# Set up convenient fuzzing defaults before initializing compiler.
	if test "x$enable_fuzzing" = xyes; then
	AC_DEFINE(NEED_FUZZING)
	test "x$CC" = x && CC=clang
	test "x$FUZZING_LIBS" = x && \
	FUZZING_LIBS="-fsanitize=fuzzer"
	test "x$SAVED_CFLAGS" = x && \
	AM_CFLAGS="-g -fsanitize=fuzzer-no-link,address"
	fi

	# Set up the compiler in two different ways and say yes we may want to install.
	AC_PROG_CC
	AM_PROG_CC_C_O
	AC_PROG_CC_C99
	AC_PROG_CPP
	AC_PROG_EGREP
	AC_PROG_INSTALL
	AC_PROG_YACC
	PKG_PROG_PKG_CONFIG
	AC_USE_SYSTEM_EXTENSIONS

	# Default tmux.conf goes in /etc not ${prefix}/etc.
	test "$sysconfdir" = '${prefix}/etc' && sysconfdir=/etc

	# Is this --enable-debug?
	case "x$VERSION" in xnext*) enable_debug=yes;; esac
	AC_ARG_ENABLE(
	debug,
	AS_HELP_STRING(--enable-debug, enable debug build flags),
	)
	AM_CONDITIONAL(IS_DEBUG, test "x$enable_debug" = xyes)

	# Is this a static build?
	AC_ARG_ENABLE(
	static,
	AS_HELP_STRING(--enable-static, create a static build)
	)
	if test "x$enable_static" = xyes; then
	test "x$PKG_CONFIG" != x && PKG_CONFIG="$PKG_CONFIG --static"
	AM_LDFLAGS="-static $AM_LDFLAGS"
	LDFLAGS="$AM_LDFLAGS $SAVED_LDFLAGS"
	fi

	# Allow default TERM to be set.
	AC_ARG_WITH(
	TERM,
	AS_HELP_STRING(--with-TERM, set default TERM),
	[DEFAULT_TERM=$withval],
	[DEFAULT_TERM=]
	)
	case "x$DEFAULT_TERM" in
	xscreen\|xtmux\|x)
	;;
	*)
	AC_MSG_ERROR("unsuitable TERM (must be screen* or tmux*)")
	;;
	esac

	# Do we need fuzzers?
	AM_CONDITIONAL(NEED_FUZZING, test "x$enable_fuzzing" = xyes)

	# Is this gcc?
	AM_CONDITIONAL(IS_GCC, test "x$GCC" = xyes -a "x$enable_fuzzing" != xyes)

	# Is this Sun CC?
	AC_EGREP_CPP(
	yes,
	[
	#ifdef __SUNPRO_C
	yes
	#endif
	],
	found_suncc=yes,
	found_suncc=no
	)
	AM_CONDITIONAL(IS_SUNCC, test "x$found_suncc" = xyes)

	# Check for various headers. Alternatives included from compat.h.
	AC_CHECK_HEADERS([ \
	bitstring.h \
	dirent.h \
	fcntl.h \
	inttypes.h \
	libproc.h \
	libutil.h \
	ndir.h \
	paths.h \
	pty.h \
	stdint.h \
	sys/dir.h \
	sys/ndir.h \
	sys/tree.h \
	util.h \
	])

	# Look for sys_signame.
	AC_SEARCH_LIBS(sys_signame, , AC_DEFINE(HAVE_SYS_SIGNAME))

	# Look for fmod.
	AC_CHECK_LIB(m, fmod)

	# Look for library needed for flock.
	AC_SEARCH_LIBS(flock, bsd)

	# Check for functions that are replaced or omitted.
	AC_CHECK_FUNCS([ \
	dirfd \
	flock \
	prctl \
	proc_pidinfo \
	sysconf
	])

	# Check for functions with a compatibility implementation.
	AC_REPLACE_FUNCS([ \
	asprintf \
	cfmakeraw \
	clock_gettime \
	closefrom \
	explicit_bzero \
	fgetln \
	freezero \
	getdtablecount \
	getdtablesize \
	getline \
	getprogname \
	memmem \
	setenv \
	setproctitle \
	strcasestr \
	strlcat \
	strlcpy \
	strndup \
	strsep \
	])
	AC_FUNC_STRNLEN

	# Check if strtonum works.
	AC_MSG_CHECKING([for working strtonum])
	AC_RUN_IFELSE([AC_LANG_PROGRAM(
	[#include <stdlib.h>],
	[return (strtonum("0", 0, 1, NULL) == 0 ? 0 : 1);]
	)],
	[AC_DEFINE(HAVE_STRTONUM) AC_MSG_RESULT(yes)],
	[AC_LIBOBJ(strtonum) AC_MSG_RESULT(no)],
	[AC_LIBOBJ(strtonum) AC_MSG_RESULT(no)]
	)

	# Clang sanitizers wrap reallocarray even if it isn't available on the target
	# system. When compiled it always returns NULL and crashes the program. To
	# detect this we need a more complicated test.
	AC_MSG_CHECKING([for working reallocarray])
	AC_RUN_IFELSE([AC_LANG_PROGRAM(
	[#include <stdlib.h>],
	[return (reallocarray(NULL, 1, 1) == NULL);]
	)],
	AC_MSG_RESULT(yes),
	[AC_LIBOBJ(reallocarray) AC_MSG_RESULT([no])],
	[AC_LIBOBJ(reallocarray) AC_MSG_RESULT([no])]
	)
	AC_MSG_CHECKING([for working recallocarray])
	AC_RUN_IFELSE([AC_LANG_PROGRAM(
	[#include <stdlib.h>],
	[return (recallocarray(NULL, 1, 1, 1) == NULL);]
	)],
	AC_MSG_RESULT(yes),
	[AC_LIBOBJ(recallocarray) AC_MSG_RESULT([no])],
	[AC_LIBOBJ(recallocarray) AC_MSG_RESULT([no])]
	)

	# Look for clock_gettime. Must come before event_init.
	AC_SEARCH_LIBS(clock_gettime, rt)

	# Always use our getopt because 1) glibc's doesn't enforce argument order 2)
	# musl does not set optarg to NULL for flags without arguments (although it is
	# not required to, but it is helpful) 3) there are probably other weird
	# implementations.
	AC_LIBOBJ(getopt)

	# Look for libevent. Try libevent_core or libevent with pkg-config first then
	# look for the library.
	PKG_CHECK_MODULES(
	LIBEVENT_CORE,
	[libevent_core >= 2],
	[
	AM_CPPFLAGS="$LIBEVENT_CORE_CFLAGS $AM_CPPFLAGS"
	CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
	LIBS="$LIBEVENT_CORE_LIBS $LIBS"
	found_libevent=yes
	],
	found_libevent=no
	)
	if test x$found_libevent = xno; then
	PKG_CHECK_MODULES(
	LIBEVENT,
	[libevent >= 2],
	[
	AM_CPPFLAGS="$LIBEVENT_CFLAGS $AM_CPPFLAGS"
	CPPFLAGS="$AM_CPPFLAGS $SAVED_CPPFLAGS"
	LIBS="$LIBEVENT_LIBS $LIBS"
	found_libevent=yes
	],
	found_libevent=no
	)
	fi
	if test x$found_libevent = xno; then
	AC_SEARCH_LIBS(
	event_init,
	[event_core event event-1.4],
	found_libevent=yes,
	found_libevent=no
	)
	fi
	AC_CHECK_HEADER(
	event2/event.h,
	AC_DEFINE(HAVE_EVENT2_EVENT_H),
	[
	AC_CHECK_HEADER(
	event.h,
	AC_DEFINE(HAVE_EVENT_H),
	found_libevent=no
	)
	]
	)
	if test "x$found_libevent" = xno; then
	AC_MSG_ERROR("libevent not found")
	fi

	# Look for ncurses or curses. Try pkg-config first then directly for the
	# library.
	PKG_CHECK_MODULES(
	LIBTINFO,
	tinfo,
	[
	AM_CPPFLAGS="$LIBTINFO_CFLAGS $AM_CPPFLAGS"
	CPPFLAGS="$LIBTINFO_CFLAGS $SAVED_CPPFLAGS"
	LIBS="$LIBTINFO_LIBS $LIBS"
	found_ncurses=yes
	],
	found_ncurses=no
	)
	if test "x$found_ncurses" = xno; then
	PKG_CHECK_MODULES(
	LIBNCURSES,
	ncurses,
	[
	AM_CPPFLAGS="$LIBNCURSES_CFLAGS $AM_CPPFLAGS"
	CPPFLAGS="$LIBNCURSES_CFLAGS $SAVED_CPPFLAGS"
	LIBS="$LIBNCURSES_LIBS $LIBS"
	found_ncurses=yes
	],
	found_ncurses=no
	)
	fi
	if test "x$found_ncurses" = xno; then
	PKG_CHECK_MODULES(
	LIBNCURSESW,
	ncursesw,
	[
	AM_CPPFLAGS="$LIBNCURSESW_CFLAGS $AM_CPPFLAGS"
	CPPFLAGS="$LIBNCURSESW_CFLAGS $SAVED_CPPFLAGS"
	LIBS="$LIBNCURSESW_LIBS $LIBS"
	found_ncurses=yes
	],
	found_ncurses=no
	)
	fi
	if test "x$found_ncurses" = xno; then
	AC_SEARCH_LIBS(
	setupterm,
	[tinfo ncurses ncursesw],
	found_ncurses=yes,
	found_ncurses=no
	)
	if test "x$found_ncurses" = xyes; then
	AC_CHECK_HEADER(
	ncurses.h,
	LIBS="$LIBS -lncurses",
	found_ncurses=no
	)
	fi
	fi
	if test "x$found_ncurses" = xyes; then
	CPPFLAGS="$CPPFLAGS -DHAVE_NCURSES_H"
	AC_DEFINE(HAVE_NCURSES_H)
	else
	AC_CHECK_LIB(
	curses,
	setupterm,
	found_curses=yes,
	found_curses=no
	)
	AC_CHECK_HEADER(
	curses.h,
	,
	found_curses=no
	)
	if test "x$found_curses" = xyes; then
	LIBS="$LIBS -lcurses"
	CPPFLAGS="$CPPFLAGS -DHAVE_CURSES_H"
	AC_DEFINE(HAVE_CURSES_H)
	else
	AC_MSG_ERROR("curses not found")
	fi
	fi

	# Look for utempter.
	AC_ARG_ENABLE(
	utempter,
	AS_HELP_STRING(--enable-utempter, use utempter if it is installed)
	)
	if test "x$enable_utempter" = xyes; then
	AC_CHECK_HEADER(utempter.h, enable_utempter=yes, enable_utempter=no)
	if test "x$enable_utempter" = xyes; then
	AC_SEARCH_LIBS(
	utempter_add_record,
	utempter,
	enable_utempter=yes,
	enable_utempter=no
	)
	fi
	if test "x$enable_utempter" = xyes; then
	AC_DEFINE(HAVE_UTEMPTER)
	else
	AC_MSG_ERROR("utempter not found")
	fi
	fi

	# Look for utf8proc.
	AC_ARG_ENABLE(
	utf8proc,
	AS_HELP_STRING(--enable-utf8proc, use utf8proc if it is installed)
	)
	if test "x$enable_utf8proc" = xyes; then
	AC_CHECK_HEADER(utf8proc.h, enable_utf8proc=yes, enable_utf8proc=no)
	if test "x$enable_utf8proc" = xyes; then
	AC_SEARCH_LIBS(
	utf8proc_charwidth,
	utf8proc,
	enable_utf8proc=yes,
	enable_utf8proc=no
	)
	fi
	if test "x$enable_utf8proc" = xyes; then
	AC_DEFINE(HAVE_UTF8PROC)
	else
	AC_MSG_ERROR("utf8proc not found")
	fi
	fi
	AM_CONDITIONAL(HAVE_UTF8PROC, [test "x$enable_utf8proc" = xyes])

	# Check for b64_ntop. If we have b64_ntop, we assume b64_pton as well.
	AC_MSG_CHECKING(for b64_ntop)
	AC_LINK_IFELSE([AC_LANG_PROGRAM(
	[
	#include <sys/types.h>
	#include <netinet/in.h>
	#include <resolv.h>
	],
	[
	b64_ntop(NULL, 0, NULL, 0);
	])],
	found_b64_ntop=yes,
	found_b64_ntop=no
	)
	AC_MSG_RESULT($found_b64_ntop)
	OLD_LIBS="$LIBS"
	if test "x$found_b64_ntop" = xno; then
	AC_MSG_CHECKING(for b64_ntop with -lresolv)
	LIBS="$OLD_LIBS -lresolv"
	AC_LINK_IFELSE([AC_LANG_PROGRAM(
	[
	#include <sys/types.h>
	#include <netinet/in.h>
	#include <resolv.h>
	],
	[
	b64_ntop(NULL, 0, NULL, 0);
	])],
	found_b64_ntop=yes,
	found_b64_ntop=no
	)
	AC_MSG_RESULT($found_b64_ntop)
	fi
	if test "x$found_b64_ntop" = xno; then
	AC_MSG_CHECKING(for b64_ntop with -lnetwork)
	LIBS="$OLD_LIBS -lnetwork"
	AC_LINK_IFELSE([AC_LANG_PROGRAM(
	[
	#include <sys/types.h>
	#include <netinet/in.h>
	#include <resolv.h>
	],
	[
	b64_ntop(NULL, 0, NULL, 0);
	])],
	found_b64_ntop=yes,
	found_b64_ntop=no
	)
	AC_MSG_RESULT($found_b64_ntop)
	fi
	if test "x$found_b64_ntop" = xyes; then
	AC_DEFINE(HAVE_B64_NTOP)
	else
	LIBS="$OLD_LIBS"
	AC_LIBOBJ(base64)
	fi

	# Look for networking libraries.
	AC_SEARCH_LIBS(inet_ntoa, nsl)
	AC_SEARCH_LIBS(socket, socket)
	AC_CHECK_LIB(xnet, socket)

	# Check if using glibc and have malloc_trim(3). The glibc free(3) is pretty bad
	# about returning memory to the kernel unless the application tells it when to
	# with malloc_trim(3).
	AC_MSG_CHECKING(if free doesn't work very well)
	AC_LINK_IFELSE([AC_LANG_SOURCE(
	[
	#include <stdlib.h>
	#ifdef __GLIBC__
	#include <malloc.h>
	int main(void) {
	malloc_trim (0);
	exit(0);
	}
	#else
	no
	#endif
	])],
	found_malloc_trim=yes,
	found_malloc_trim=no
	)
	AC_MSG_RESULT($found_malloc_trim)
	if test "x$found_malloc_trim" = xyes; then
	AC_DEFINE(HAVE_MALLOC_TRIM)
	fi

	# Check for CMSG_DATA. On some platforms like HP-UX this requires UNIX 95
	# (_XOPEN_SOURCE and _XOPEN_SOURCE_EXTENDED) (see xopen_networking(7)). On
	# others, UNIX 03 (_XOPEN_SOURCE 600, see standards(7) on Solaris).
	XOPEN_DEFINES=
	AC_MSG_CHECKING(for CMSG_DATA)
	AC_EGREP_CPP(
	yes,
	[
	#include <sys/socket.h>
	#ifdef CMSG_DATA
	yes
	#endif
	],
	found_cmsg_data=yes,
	found_cmsg_data=no
	)
	AC_MSG_RESULT($found_cmsg_data)
	if test "x$found_cmsg_data" = xno; then
	AC_MSG_CHECKING(if CMSG_DATA needs _XOPEN_SOURCE_EXTENDED)
	AC_EGREP_CPP(
	yes,
	[
	#define _XOPEN_SOURCE 1
	#define _XOPEN_SOURCE_EXTENDED 1
	#include <sys/socket.h>
	#ifdef CMSG_DATA
	yes
	#endif
	],
	found_cmsg_data=yes,
	found_cmsg_data=no
	)
	AC_MSG_RESULT($found_cmsg_data)
	if test "x$found_cmsg_data" = xyes; then
	XOPEN_DEFINES="-D_XOPEN_SOURCE -D_XOPEN_SOURCE_EXTENDED"
	fi
	fi
	if test "x$found_cmsg_data" = xno; then
	AC_MSG_CHECKING(if CMSG_DATA needs _XOPEN_SOURCE 600)
	AC_EGREP_CPP(
	yes,
	[
	#define _XOPEN_SOURCE 600
	#include <sys/socket.h>
	#ifdef CMSG_DATA
	yes
	#endif
	],
	found_cmsg_data=yes,
	found_cmsg_data=no
	)
	AC_MSG_RESULT($found_cmsg_data)
	if test "x$found_cmsg_data" = xyes; then
	XOPEN_DEFINES="-D_XOPEN_SOURCE=600"
	else
	AC_MSG_ERROR("CMSG_DATA not found")
	fi
	fi
	AC_SUBST(XOPEN_DEFINES)

	# Look for err and friends in err.h.
	AC_CHECK_FUNC(err, found_err_h=yes, found_err_h=no)
	AC_CHECK_FUNC(errx, , found_err_h=no)
	AC_CHECK_FUNC(warn, , found_err_h=no)
	AC_CHECK_FUNC(warnx, , found_err_h=no)
	if test "x$found_err_h" = xyes; then
	AC_CHECK_HEADER(err.h, , found_err_h=no)
	else
	AC_LIBOBJ(err)
	fi

	# Look for imsg_init in libutil.
	AC_SEARCH_LIBS(imsg_init, util, found_imsg_init=yes, found_imsg_init=no)
	if test "x$found_imsg_init" = xyes; then
	AC_DEFINE(HAVE_IMSG)
	else
	AC_LIBOBJ(imsg)
	AC_LIBOBJ(imsg-buffer)
	fi

	# Look for daemon, compat/daemon.c used if missing. Solaris 10 has it in
	# libresolv, but no declaration anywhere, so check for declaration as well as
	# function.
	AC_CHECK_FUNC(daemon, found_daemon=yes, found_daemon=no)
	AC_CHECK_DECL(
	daemon,
	,
	found_daemon=no,
	[
	#include <stdlib.h>
	#include <unistd.h>
	]
	)
	if test "x$found_daemon" = xyes; then
	AC_DEFINE(HAVE_DAEMON)
	else
	AC_LIBOBJ(daemon)
	fi

	# Look for stravis, compat/{vis,unvis}.c used if missing.
	AC_CHECK_FUNC(stravis, found_stravis=yes, found_stravis=no)
	if test "x$found_stravis" = xyes; then
	AC_MSG_CHECKING(if strnvis is broken)
	AC_EGREP_HEADER([strnvis\(char \, const char \, size_t, int\)],
	vis.h,
	AC_MSG_RESULT(no),
	[found_stravis=no])
	if test "x$found_stravis" = xno; then
	AC_MSG_RESULT(yes)
	fi
	fi
	if test "x$found_stravis" = xyes; then
	AC_CHECK_DECL(
	VIS_DQ,
	,
	found_stravis=no,
	[
	#include <stdlib.h>
	#include <vis.h>
	]
	)
	fi
	if test "x$found_stravis" = xyes; then
	AC_DEFINE(HAVE_VIS)
	else
	AC_LIBOBJ(vis)
	AC_LIBOBJ(unvis)
	fi

	# Look for fdforkpty and forkpty in libutil.
	AC_SEARCH_LIBS(fdforkpty, util, found_fdforkpty=yes, found_fdforkpty=no)
	if test "x$found_fdforkpty" = xyes; then
	AC_DEFINE(HAVE_FDFORKPTY)
	else
	AC_LIBOBJ(fdforkpty)
	fi
	AC_SEARCH_LIBS(forkpty, util, found_forkpty=yes, found_forkpty=no)
	if test "x$found_forkpty" = xyes; then
	AC_DEFINE(HAVE_FORKPTY)
	fi
	AM_CONDITIONAL(NEED_FORKPTY, test "x$found_forkpty" = xno)

	# Look for kinfo_getfile in libutil.
	AC_SEARCH_LIBS(kinfo_getfile, [util util-freebsd])

	# Look for a suitable queue.h.
	AC_CHECK_DECL(
	TAILQ_CONCAT,
	found_queue_h=yes,
	found_queue_h=no,
	[#include <sys/queue.h>]
	)
	AC_CHECK_DECL(
	TAILQ_PREV,
	,
	found_queue_h=no,
	[#include <sys/queue.h>]
	)
	AC_CHECK_DECL(
	TAILQ_REPLACE,
	,
	found_queue_h=no,
	[#include <sys/queue.h>]
	)
	if test "x$found_queue_h" = xyes; then
	AC_DEFINE(HAVE_QUEUE_H)
	fi

	# Look for __progname.
	AC_MSG_CHECKING(for __progname)
	AC_LINK_IFELSE([AC_LANG_SOURCE(
	[
	#include <stdio.h>
	#include <stdlib.h>
	extern char *__progname;
	int main(void) {
	const char *cp = __progname;
	printf("%s\n", cp);
	exit(0);
	}
	])],
	[AC_DEFINE(HAVE___PROGNAME) AC_MSG_RESULT(yes)],
	AC_MSG_RESULT(no)
	)

	# Look for program_invocation_short_name.
	AC_MSG_CHECKING(for program_invocation_short_name)
	AC_LINK_IFELSE([AC_LANG_SOURCE(
	[
	#include <errno.h>
	#include <stdio.h>
	#include <stdlib.h>
	int main(void) {
	const char *cp = program_invocation_short_name;
	printf("%s\n", cp);
	exit(0);
	}
	])],
	[AC_DEFINE(HAVE_PROGRAM_INVOCATION_SHORT_NAME) AC_MSG_RESULT(yes)],
	AC_MSG_RESULT(no)
	)

	# Look for prctl(PR_SET_NAME).
	AC_CHECK_DECL(
	PR_SET_NAME,
	AC_DEFINE(HAVE_PR_SET_NAME),
	,
	[#include <sys/prctl.h>]
	)

	# Look for fcntl(F_CLOSEM).
	AC_CHECK_DECL(
	F_CLOSEM,
	AC_DEFINE(HAVE_FCNTL_CLOSEM),
	,
	[#include <fcntl.h>]
	)

	# Look for /proc/$$.
	AC_MSG_CHECKING(for /proc/\$\$)
	if test -d /proc/$$; then
	AC_DEFINE(HAVE_PROC_PID)
	AC_MSG_RESULT(yes)
	else
	AC_MSG_RESULT(no)
	fi

	# Try to figure out what the best value for TERM might be.
	if test "x$DEFAULT_TERM" = x; then
	DEFAULT_TERM=screen
	AC_MSG_CHECKING(TERM)
	AC_RUN_IFELSE([AC_LANG_SOURCE(
	[
	#include <stdio.h>
	#include <stdlib.h>
	#if defined(HAVE_CURSES_H)
	#include <curses.h>
	#elif defined(HAVE_NCURSES_H)
	#include <ncurses.h>
	#endif
	#include <term.h>
	int main(void) {
	if (setupterm("screen-256color", -1, NULL) != OK)
	exit(1);
	exit(0);
	}
	])],
	[DEFAULT_TERM=screen-256color],
	,
	[DEFAULT_TERM=screen]
	)
	AC_RUN_IFELSE([AC_LANG_SOURCE(
	[
	#include <stdio.h>
	#include <stdlib.h>
	#if defined(HAVE_CURSES_H)
	#include <curses.h>
	#elif defined(HAVE_NCURSES_H)
	#include <ncurses.h>
	#endif
	#include <term.h>
	int main(void) {
	if (setupterm("tmux", -1, NULL) != OK)
	exit(1);
	exit(0);
	}
	])],
	[DEFAULT_TERM=tmux],
	,
	[DEFAULT_TERM=screen]
	)
	AC_RUN_IFELSE([AC_LANG_SOURCE(
	[
	#include <stdio.h>
	#include <stdlib.h>
	#if defined(HAVE_CURSES_H)
	#include <curses.h>
	#elif defined(HAVE_NCURSES_H)
	#include <ncurses.h>
	#endif
	#include <term.h>
	int main(void) {
	if (setupterm("tmux-256color", -1, NULL) != OK)
	exit(1);
	exit(0);
	}
	])],
	[DEFAULT_TERM=tmux-256color],
	,
	[DEFAULT_TERM=screen]
	)
	AC_MSG_RESULT($DEFAULT_TERM)
	fi
	AC_SUBST(DEFAULT_TERM)

	# Man page defaults to mdoc.
	MANFORMAT=mdoc
	AC_SUBST(MANFORMAT)

	# Figure out the platform.
	AC_MSG_CHECKING(platform)
	case "$host_os" in
	aix)
	AC_MSG_RESULT(aix)
	PLATFORM=aix
	;;
	darwin)
	AC_MSG_RESULT(darwin)
	PLATFORM=darwin
	#
	# macOS uses __dead2 instead of __dead, like FreeBSD. But it defines
	# __dead away so it needs to be removed before we can replace it.
	#
	AC_DEFINE(BROKEN___DEAD)
	#
	# macOS CMSG_FIRSTHDR is broken, so redefine it with a working one.
	# daemon works but has some stupid side effects, so use our internal
	# version which has a workaround.
	#
	AC_DEFINE(BROKEN_CMSG_FIRSTHDR)
	AC_LIBOBJ(daemon)
	AC_LIBOBJ(daemon-darwin)
	#
	# macOS wcwidth(3) is bad, so complain and suggest using utf8proc
	# instead.
	#
	if test "x$enable_utf8proc" = x; then
	AC_MSG_NOTICE([])
	AC_MSG_NOTICE([ macOS library support for Unicode is very poor,])
	AC_MSG_NOTICE([ particularly for complex codepoints like emojis;])
	AC_MSG_NOTICE([ to use these correctly, configuring with])
	AC_MSG_NOTICE([ --enable-utf8proc is recommended. To build])
	AC_MSG_NOTICE([ without anyway, use --disable-utf8proc])
	AC_MSG_NOTICE([])
	AC_MSG_ERROR([must give --enable-utf8proc or --disable-utf8proc])
	fi
	;;
	dragonfly)
	AC_MSG_RESULT(dragonfly)
	PLATFORM=dragonfly
	;;
	linux)
	AC_MSG_RESULT(linux)
	PLATFORM=linux
	;;
	freebsd)
	AC_MSG_RESULT(freebsd)
	PLATFORM=freebsd
	;;
	netbsd)
	AC_MSG_RESULT(netbsd)
	PLATFORM=netbsd
	;;
	openbsd)
	AC_MSG_RESULT(openbsd)
	PLATFORM=openbsd
	;;
	sunos)
	AC_MSG_RESULT(sunos)
	PLATFORM=sunos
	;;
	solaris)
	AC_MSG_RESULT(sunos)
	PLATFORM=sunos
	case `/usr/bin/nroff --version 2>&1` in
	GNU)
	# Solaris 11.4 and later use GNU groff.
	MANFORMAT=mdoc
	;;
	*)
	# Solaris 2.0 to 11.3 use AT&T nroff.
	MANFORMAT=man
	;;
	esac
	;;
	hpux)
	AC_MSG_RESULT(hpux)
	PLATFORM=hpux
	;;
	cygwin\|msys)
	AC_MSG_RESULT(cygwin)
	PLATFORM=cygwin
	;;
	haiku)
	AC_MSG_RESULT(haiku)
	PLATFORM=haiku
	;;
	*)
	AC_MSG_RESULT(unknown)
	PLATFORM=unknown
	;;
	esac
	AC_SUBST(PLATFORM)
	AM_CONDITIONAL(IS_AIX, test "x$PLATFORM" = xaix)
	AM_CONDITIONAL(IS_DARWIN, test "x$PLATFORM" = xdarwin)
	AM_CONDITIONAL(IS_DRAGONFLY, test "x$PLATFORM" = xdragonfly)
	AM_CONDITIONAL(IS_LINUX, test "x$PLATFORM" = xlinux)
	AM_CONDITIONAL(IS_FREEBSD, test "x$PLATFORM" = xfreebsd)
	AM_CONDITIONAL(IS_NETBSD, test "x$PLATFORM" = xnetbsd)
	AM_CONDITIONAL(IS_OPENBSD, test "x$PLATFORM" = xopenbsd)
	AM_CONDITIONAL(IS_SUNOS, test "x$PLATFORM" = xsunos)
	AM_CONDITIONAL(IS_HPUX, test "x$PLATFORM" = xhpux)
	AM_CONDITIONAL(IS_HAIKU, test "x$PLATFORM" = xhaiku)
	AM_CONDITIONAL(IS_UNKNOWN, test "x$PLATFORM" = xunknown)

	# Save our CFLAGS/CPPFLAGS/LDFLAGS for the Makefile and restore the old user
	# variables.
	AC_SUBST(AM_CPPFLAGS)
	CPPFLAGS="$SAVED_CPPFLAGS"
	AC_SUBST(AM_CFLAGS)
	CFLAGS="$SAVED_CFLAGS"
	AC_SUBST(AM_LDFLAGS)
	LDFLAGS="$SAVED_LDFLAGS"

	# autoconf should create a Makefile.
	AC_CONFIG_FILES(Makefile)
	AC_OUTPUT