configure.ac - third_party/libusb - Git at Google

 dnl These m4 macros are whitespace sensitive and break if moved around much.
 m4_define([LU_VERSION_H], m4_include([libusb/version.h]))
 m4_define([LU_DEFINE_VERSION_ATOM],
 	[m4_define([$1], m4_bregexp(LU_VERSION_H,
 	[^#define\s*$1\s*\([0-9]*\).*], [\1]))])
 m4_define([LU_DEFINE_VERSION_RC_ATOM],
 	[m4_define([$1], m4_bregexp(LU_VERSION_H,
 	[^#define\s*$1\s*"\(-rc[0-9]*\)".*], [\1]))])
 dnl The m4_bregexp() returns (only) the numbers following the #define named
 dnl in the first macro parameter. m4_define() then defines the name for use
 dnl in AC_INIT.

 LU_DEFINE_VERSION_ATOM([LIBUSB_MAJOR])
 LU_DEFINE_VERSION_ATOM([LIBUSB_MINOR])
 LU_DEFINE_VERSION_ATOM([LIBUSB_MICRO])
 LU_DEFINE_VERSION_RC_ATOM([LIBUSB_RC])

 AC_PREREQ([2.69])
 AC_INIT([libusb-1.0], [LIBUSB_MAJOR[.]LIBUSB_MINOR[.]LIBUSB_MICRO[]LIBUSB_RC], [libusb-devel@lists.sourceforge.net], [libusb-1.0], [http://libusb.info])
 AC_CONFIG_HEADERS([config.h])
 AC_CONFIG_SRCDIR([libusb/core.c])
 AC_CONFIG_MACRO_DIR([m4])
 AC_PROG_CC
 AC_PROG_CXX
 AC_C_INLINE
 AM_INIT_AUTOMAKE
 LT_INIT
 LT_LANG([Windows Resource])

 dnl Library versioning
 dnl These numbers should be tweaked on every release. Read carefully:
 dnl http://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
 dnl http://sourceware.org/autobook/autobook/autobook_91.html
 lt_current=3
 lt_revision=0
 lt_age=3
 LT_LDFLAGS="-version-info ${lt_current}:${lt_revision}:${lt_age} -no-undefined"

 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])

 EXTRA_CPPFLAGS=
 EXTRA_CFLAGS=

 dnl check for -std=gnu11 compiler support (optional)
 dnl note that we don't just check if the compiler accepts '-std=x11'
 dnl but also that it supports the _Thread_local keyword because some compilers
 dnl (e.g. gcc 4.8) accept the command line option but do not implement TLS
 saved_CFLAGS="${CFLAGS}"
 CFLAGS="-std=gnu11"
 AC_MSG_CHECKING([if $CC supports -std=gnu11])
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([_Thread_local int x;], [x = 42;])],
 	[AC_MSG_RESULT([yes])
 	 c_dialect=gnu],
 	[AC_MSG_RESULT([no])
 	 c_dialect=])
 if test "x$c_dialect" != xgnu; then
 	dnl fallback check for -std=c11 compiler support (required)
 	CFLAGS="-std=c11"
 	AC_MSG_CHECKING([if $CC supports -std=c11])
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([_Thread_local int x;], [x = 42;])],
 		[AC_MSG_RESULT([yes])],
 		[AC_MSG_RESULT([no])
 		 AC_MSG_ERROR([compiler with C11 support is required to build libusb])])
 	c_dialect=c
 fi
 CFLAGS="${saved_CFLAGS}"

 AC_DEFINE([_GNU_SOURCE], [1], [Enable GNU extensions.])
 AC_DEFINE([DEFAULT_VISIBILITY], [__attribute__ ((visibility ("default")))], [Define to the attribute for default visibility.])
 AC_DEFINE([PRINTF_FORMAT(a, b)], [__attribute__ ((__format__ (__printf__, a, b)))], [Define to the attribute for enabling parameter checks on printf-like functions.])

 create_import_lib=
 is_android_linux=
 AC_MSG_CHECKING([operating system])
 case $host in
 *-darwin*)
 	AC_MSG_RESULT([Darwin/Mac OS X])
 	backend=darwin
 	platform=posix
 	;;
 *-haiku*)
 	AC_MSG_RESULT([Haiku])
 	backend=haiku
 	platform=posix
 	;;
 *-linux* | *-uclinux*)
 	dnl on Android Linux, some functions are in different places
 	case $host in
 	*-linux-android*)
 		AC_MSG_RESULT([Android Linux])
 		is_android_linux=yes
 		;;
 	*)
 		AC_MSG_RESULT([Linux])
 		;;
 	esac
 	backend=linux
 	platform=posix
 	;;
 *-netbsd*)
 	AC_MSG_RESULT([NetBSD])
 	backend=netbsd
 	platform=posix
 	;;
 *-openbsd*)
 	AC_MSG_RESULT([OpenBSD])
 	backend=openbsd
 	platform=posix
 	;;
 *-solaris*)
 	AC_MSG_RESULT([SunOS])
 	backend=sunos
 	platform=posix
 	;;
 *-cygwin*)
 	AC_MSG_RESULT([Windows (using Cygwin)])
 	backend=windows
 	platform=windows
 	EXTRA_CFLAGS="-mwin32"
 	;;
 *-mingw* | *msys*)
 	AC_MSG_RESULT([Windows])
 	backend=windows
 	platform=windows
 	test "x$enable_shared" = xyes && create_import_lib=yes
 	EXTRA_CFLAGS="-mwin32 -fno-omit-frame-pointer"
 	EXTRA_LDFLAGS="-static-libgcc"
 	;;
 *)
 	AC_MSG_RESULT([Null])
 	AC_MSG_WARN([The host being compiled for is not supported.])
 	AC_MSG_WARN([The library may compile but will not function in any useful manner.])
 	backend=null
 	platform=posix
 	;;
 esac

 if test "x$platform" = xposix; then
 	AC_DEFINE([PLATFORM_POSIX], [1], [Define to 1 if compiling for a POSIX platform.])
 	AC_CHECK_TYPES([nfds_t], [], [], [[#include <poll.h>]])
 	AC_CHECK_FUNCS([pipe2])
 	dnl Some compilers do not support the '-pthread' option so check for it here
 	saved_CFLAGS="${CFLAGS}"
 	CFLAGS="-Wall -Werror -pthread"
 	AC_MSG_CHECKING([if $CC recognizes -pthread])
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
 		[AC_MSG_RESULT([yes])
 		 AC_SUBST(THREAD_CFLAGS, [-pthread])],
 		[AC_MSG_RESULT([no])])
 	CFLAGS="${saved_CFLAGS}"
 	dnl Android Linux and Darwin provide pthread functions directly in libc
 	dnl glibc also provides some pthread functions directly, so search for a thread-specific function
 	AC_SEARCH_LIBS([pthread_create], [pthread],
 		[test "x$ac_cv_search_pthread_create" != "xnone required" && AC_SUBST(THREAD_LIBS, [-lpthread])],
 		[], [])
 	AC_SEARCH_LIBS([__atomic_fetch_add_4], [atomic])
 elif test "x$platform" = xwindows; then
 	AC_DEFINE([PLATFORM_WINDOWS], [1], [Define to 1 if compiling for a Windows platform.])
 else
 	AC_MSG_ERROR([Unknown platform])
 fi

 case $backend in
 darwin)
 	AC_CHECK_FUNCS([pthread_threadid_np])
 	LIBS="${LIBS} -lobjc -Wl,-framework,IOKit -Wl,-framework,CoreFoundation -Wl,-framework,Security"
 	AC_CHECK_HEADERS([IOKit/usb/IOUSBHostFamilyDefinitions.h])
 	;;
 haiku)
 	LIBS="${LIBS} -lbe"
 	;;
 linux)
 	AC_SEARCH_LIBS([clock_gettime], [rt], [], [], [])
 	AC_CHECK_FUNCS([pthread_setname_np])
 	AC_ARG_ENABLE([udev],
 		[AS_HELP_STRING([--enable-udev], [use udev for device enumeration and hotplug support (recommended) [default=yes]])],
 		[use_udev=$enableval], [use_udev=yes])
 	if test "x$use_udev" = xyes; then
 		dnl system has udev. use it or fail!
 		AC_CHECK_HEADER([libudev.h], [], [AC_MSG_ERROR([udev support requested but libudev header not installed])])
 		AC_CHECK_LIB([udev], [udev_new], [], [AC_MSG_ERROR([udev support requested but libudev not installed])])

 		# We can build umockdev tests (if available)
 		PKG_PROG_PKG_CONFIG
 		PKG_CHECK_MODULES(UMOCKDEV, umockdev-1.0 >= 0.16.0, ac_have_umockdev=yes, ac_have_umockdev=no)
 		PKG_CHECK_MODULES(UMOCKDEV_HOTPLUG, umockdev-1.0 >= 0.17.7, ac_umockdev_hotplug=yes, ac_umockdev_hotplug=no)
 		if test "x$ac_umockdev_hotplug" = xyes; then
 			AC_DEFINE([UMOCKDEV_HOTPLUG], [1], [UMockdev hotplug code is not racy])
 		fi
 	else
 		AC_CHECK_HEADERS([asm/types.h])
 		AC_CHECK_HEADER([linux/netlink.h], [], [AC_MSG_ERROR([Linux netlink header not found])])
 		AC_CHECK_HEADER([sys/socket.h], [], [AC_MSG_ERROR([Linux socket header not found])])
 	fi
 	;;
 sunos)
 	LIBS="${LIBS} -ldevinfo"
 	;;
 windows)
 	AC_CHECK_TYPES([struct timespec], [], [], [[#include <time.h>]])
 	AC_DEFINE([_WIN32_WINNT], [_WIN32_WINNT_VISTA], [Define to the oldest supported Windows version.])
 	LT_LDFLAGS="${LT_LDFLAGS} -avoid-version -Wl,--add-stdcall-alias"
 	;;
 *)
 	dnl no special handling required
 	;;
 esac

 dnl headers not available on all platforms but required on others
 AC_CHECK_HEADERS([sys/time.h])

 if test "x$platform" = xposix; then
 	dnl check availability of clock_gettime()
 	if test "x$backend" = xdarwin; then
 		dnl need to verify that OS X target is 10.12 or later for clock_gettime()
 		AC_MSG_CHECKING([whether OS X target version is 10.12 or later])
 		AC_COMPILE_IFELSE([AC_LANG_PROGRAM([
 				#include <AvailabilityMacros.h>
 				#if MAC_OS_X_VERSION_MIN_REQUIRED < 101200
 				# error "Target OS X version is too old"
 				#endif
 			], [])],
 			[AC_MSG_RESULT([yes])
 			 osx_10_12_or_later=yes],
 			[AC_MSG_RESULT([no])
 			 osx_10_12_or_later=])
 		if test "x$osx_10_12_or_later" = xyes; then
 			AC_CHECK_FUNCS([clock_gettime], [have_clock_gettime=yes], [have_clock_gettime=])
 		else
 			AC_MSG_NOTICE([clock_gettime() is not available on target OS X version])
 		fi
 	else
 		AC_CHECK_FUNCS([clock_gettime], [have_clock_gettime=yes], [AC_MSG_ERROR([clock_gettime() is required on this platform])])
 	fi

 	if test "x$have_clock_gettime" = xyes; then
 		dnl the clock_gettime() function needs certain clock IDs defined
 		AC_CHECK_DECL([CLOCK_MONOTONIC], [], [AC_MSG_ERROR([C library headers missing definition for CLOCK_MONOTONIC])], [[#include <time.h>]])
 		dnl use the monotonic clock for condition variable timed waits if possible
 		AC_CHECK_FUNCS([pthread_condattr_setclock], [need_clock_realtime=], [need_clock_realtime=yes])
 		if test "x$need_clock_realtime" = xyes; then
 			AC_CHECK_DECL([CLOCK_REALTIME], [], [AC_MSG_ERROR([C library headers missing definition for CLOCK_REALTIME])], [[#include <time.h>]])
 		fi
 	fi
 fi

 dnl eventfd support
 if test "x$backend" = xlinux || test "x$backend" = xsunos; then
 	AC_ARG_ENABLE([eventfd],
 		[AS_HELP_STRING([--enable-eventfd], [use eventfd for signalling [default=auto]])],
 		[use_eventfd=$enableval],
 		[use_eventfd=auto])
 	if test "x$use_eventfd" != xno; then
 		AC_CHECK_HEADER([sys/eventfd.h], [eventfd_h=yes], [eventfd_h=])
 		if test "x$eventfd_h" = xyes; then
 			AC_CHECK_DECLS([EFD_NONBLOCK, EFD_CLOEXEC], [eventfd_h_ok=yes], [eventfd_h_ok=], [[#include <sys/eventfd.h>]])
 			if test "x$eventfd_h_ok" = xyes; then
 				AC_CHECK_FUNC([eventfd], [eventfd_ok=yes], [eventfd_ok=])
 				if test "x$eventfd_ok" = xyes; then
 					AC_DEFINE([HAVE_EVENTFD], [1], [Define to 1 if the system has eventfd functionality.])
 				elif test "x$use_eventfd" = xyes; then
 					AC_MSG_ERROR([eventfd() function not found; glibc 2.9+ required])
 				fi
 			elif test "x$use_eventfd" = xyes; then
 				AC_MSG_ERROR([eventfd header not usable; glibc 2.9+ required])
 			fi
 		elif test "x$use_eventfd" = xyes; then
 			AC_MSG_ERROR([eventfd header not available; glibc 2.9+ required])
 		fi
 	fi
 	AC_MSG_CHECKING([whether to use eventfd for signalling])
 	if test "x$use_eventfd" = xno; then
 		AC_MSG_RESULT([no (disabled by user)])
 	elif test "x$eventfd_h" != xyes; then
 		AC_MSG_RESULT([no (header not available)])
 	elif test "x$eventfd_h_ok" != xyes; then
 		AC_MSG_RESULT([no (header not usable)])
 	elif test "x$eventfd_ok" != xyes; then
 		AC_MSG_RESULT([no (functions not available)])
 	else
 		AC_MSG_RESULT([yes])
 	fi
 fi

 dnl timerfd support
 if test "x$backend" = xlinux || test "x$backend" = xsunos; then
 	AC_ARG_ENABLE([timerfd],
 		[AS_HELP_STRING([--enable-timerfd], [use timerfd for timing [default=auto]])],
 		[use_timerfd=$enableval],
 		[use_timerfd=auto])
 	if test "x$use_timerfd" != xno; then
 		AC_CHECK_HEADER([sys/timerfd.h], [timerfd_h=yes], [timerfd_h=])
 		if test "x$timerfd_h" = xyes; then
 			AC_CHECK_DECLS([TFD_NONBLOCK, TFD_CLOEXEC], [timerfd_h_ok=yes], [timerfd_h_ok=], [[#include <sys/timerfd.h>]])
 			if test "x$timerfd_h_ok" = xyes; then
 				AC_CHECK_FUNC([timerfd_create], [timerfd_ok=yes], [timerfd_ok=])
 				if test "x$timerfd_ok" = xyes; then
 					AC_DEFINE([HAVE_TIMERFD], [1], [Define to 1 if the system has timerfd functionality.])
 				elif test "x$use_timerfd" = xyes; then
 					AC_MSG_ERROR([timerfd_create() function not found; glibc 2.9+ required])
 				fi
 			elif test "x$use_timerfd" = xyes; then
 				AC_MSG_ERROR([timerfd header not usable; glibc 2.9+ required])
 			fi
 		elif test "x$use_timerfd" = xyes; then
 			AC_MSG_ERROR([timerfd header not available; glibc 2.9+ required])
 		fi
 	fi
 	AC_MSG_CHECKING([whether to use timerfd for timing])
 	if test "x$use_timerfd" = xno; then
 		AC_MSG_RESULT([no (disabled by user)])
 	elif test "x$timerfd_h" != xyes; then
 		AC_MSG_RESULT([no (header not available)])
 	elif test "x$timerfd_h_ok" != xyes; then
 		AC_MSG_RESULT([no (header not usable)])
 	elif test "x$timerfd_ok" != xyes; then
 		AC_MSG_RESULT([no (functions not available)])
 	else
 		AC_MSG_RESULT([yes])
 	fi
 fi

 dnl Message logging
 AC_ARG_ENABLE([log],
 	[AS_HELP_STRING([--disable-log], [disable all logging])],
 	[log_enabled=$enableval],
 	[log_enabled=yes])
 if test "x$log_enabled" != xno; then
 	AC_DEFINE([ENABLE_LOGGING], [1], [Define to 1 to enable message logging.])
 fi

 AC_ARG_ENABLE([debug-log],
 	[AS_HELP_STRING([--enable-debug-log], [start with debug message logging enabled [default=no]])],
 	[debug_log_enabled=$enableval],
 	[debug_log_enabled=no])
 if test "x$debug_log_enabled" != xno; then
 	AC_DEFINE([ENABLE_DEBUG_LOGGING], [1], [Define to 1 to start with debug message logging enabled.])
 fi

 AC_ARG_ENABLE([system-log],
 	[AS_HELP_STRING([--enable-system-log], [output logging messages to the systemwide log, if supported by the OS [default=no]])],
 	[system_log_enabled=$enableval],
 	[system_log_enabled=no])
 if test "x$system_log_enabled" != xno; then
 	AC_DEFINE([USE_SYSTEM_LOGGING_FACILITY], [1], [Define to 1 to output logging messages to the systemwide log.])
 	if test "x$backend" != xwindows && test "x$is_android_linux" != xyes; then
 		dnl Check if syslog is available in standard C library
 		AC_CHECK_HEADER([syslog.h], [syslog_h=yes], [syslog_h=])
 		if test "x$syslog_h" = xyes; then
 			AC_CHECK_FUNCS([syslog])
 		fi
 	fi
 fi

 dnl Examples build
 AC_ARG_ENABLE([examples-build],
 	[AS_HELP_STRING([--enable-examples-build], [build example applications [default=no]])],
 	[build_examples=$enableval],
 	[build_examples=no])

 dnl Tests build
 AC_ARG_ENABLE([tests-build],
 	[AS_HELP_STRING([--enable-tests-build], [build test applications [default=no]])],
 	[build_tests=$enableval],
 	[build_tests=no])

 AM_CONDITIONAL([BUILD_EXAMPLES], [test "x$build_examples" != xno])
 AM_CONDITIONAL([BUILD_TESTS], [test "x$build_tests" != xno])
 AM_CONDITIONAL([BUILD_UMOCKDEV_TEST], [test "x$ac_have_umockdev" = xyes -a "x$log_enabled" != xno])
 AM_CONDITIONAL([CREATE_IMPORT_LIB], [test "x$create_import_lib" = xyes])
 AM_CONDITIONAL([OS_DARWIN], [test "x$backend" = xdarwin])
 AM_CONDITIONAL([OS_HAIKU], [test "x$backend" = xhaiku])
 AM_CONDITIONAL([OS_LINUX], [test "x$backend" = xlinux])
 AM_CONDITIONAL([OS_NETBSD], [test "x$backend" = xnetbsd])
 AM_CONDITIONAL([OS_NULL], [test "x$backend" = xnull])
 AM_CONDITIONAL([OS_OPENBSD], [test "x$backend" = xopenbsd])
 AM_CONDITIONAL([OS_SUNOS], [test "x$backend" = xsunos])
 AM_CONDITIONAL([OS_WINDOWS], [test "x$backend" = xwindows])
 AM_CONDITIONAL([PLATFORM_POSIX], [test "x$platform" = xposix])
 AM_CONDITIONAL([PLATFORM_WINDOWS], [test "x$platform" = xwindows])
 AM_CONDITIONAL([USE_UDEV], [test "x$use_udev" = xyes])

 dnl The -Wcast-function-type warning causes a flurry of warnings when compiling
 dnl Windows with GCC 8 or later because of dynamically loaded functions
 if test "x$backend" = xwindows; then
 	saved_CFLAGS="${CFLAGS}"
 	CFLAGS="-Werror -Wcast-function-type"
 	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
 		[EXTRA_CFLAGS="${EXTRA_CFLAGS} -Wno-cast-function-type"],
 		[])
 	CFLAGS="${saved_CFLAGS}"
 fi

 SHARED_CFLAGS="-Wall -Wextra -Wshadow -Wunused -Wwrite-strings -Werror=format-security -Werror=implicit-function-declaration -Werror=implicit-int -Werror=init-self -Werror=missing-prototypes -Werror=strict-prototypes -Werror=undef -Werror=uninitialized"

 AM_CPPFLAGS="${EXTRA_CPPFLAGS}"
 AC_SUBST(AM_CPPFLAGS)

 AM_CFLAGS="-std=${c_dialect}11 ${EXTRA_CFLAGS} ${SHARED_CFLAGS}"
 AC_SUBST(AM_CFLAGS)

 AM_CXXFLAGS="-std=${c_dialect}++11 ${EXTRA_CFLAGS} ${SHARED_CFLAGS} -Wmissing-declarations"
 AC_SUBST(AM_CXXFLAGS)

 AC_SUBST(LT_LDFLAGS)

 AC_SUBST([EXTRA_LDFLAGS])

 dnl set name of html output directory for doxygen
 AC_SUBST(DOXYGEN_HTMLDIR, [api-1.0])

 AC_CONFIG_FILES([libusb-1.0.pc])
 AC_CONFIG_FILES([Makefile])
 AC_CONFIG_FILES([libusb/Makefile])
 AC_CONFIG_FILES([examples/Makefile])
 AC_CONFIG_FILES([tests/Makefile])
 AC_CONFIG_FILES([doc/Makefile])
 AC_CONFIG_FILES([doc/doxygen.cfg])
 AC_OUTPUT
	dnl These m4 macros are whitespace sensitive and break if moved around much.
	m4_define([LU_VERSION_H], m4_include([libusb/version.h]))
	m4_define([LU_DEFINE_VERSION_ATOM],
	[m4_define([$1], m4_bregexp(LU_VERSION_H,
	[^#define\s$1\s\([0-9]\).], [\1]))])
	m4_define([LU_DEFINE_VERSION_RC_ATOM],
	[m4_define([$1], m4_bregexp(LU_VERSION_H,
	[^#define\s$1\s"\(-rc[0-9]\)".], [\1]))])
	dnl The m4_bregexp() returns (only) the numbers following the #define named
	dnl in the first macro parameter. m4_define() then defines the name for use
	dnl in AC_INIT.

	LU_DEFINE_VERSION_ATOM([LIBUSB_MAJOR])
	LU_DEFINE_VERSION_ATOM([LIBUSB_MINOR])
	LU_DEFINE_VERSION_ATOM([LIBUSB_MICRO])
	LU_DEFINE_VERSION_RC_ATOM([LIBUSB_RC])

	AC_PREREQ([2.69])
	AC_INIT([libusb-1.0], [LIBUSB_MAJOR[.]LIBUSB_MINOR[.]LIBUSB_MICRO[]LIBUSB_RC], [libusb-devel@lists.sourceforge.net], [libusb-1.0], [http://libusb.info])
	AC_CONFIG_HEADERS([config.h])
	AC_CONFIG_SRCDIR([libusb/core.c])
	AC_CONFIG_MACRO_DIR([m4])
	AC_PROG_CC
	AC_PROG_CXX
	AC_C_INLINE
	AM_INIT_AUTOMAKE
	LT_INIT
	LT_LANG([Windows Resource])

	dnl Library versioning
	dnl These numbers should be tweaked on every release. Read carefully:
	dnl http://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html
	dnl http://sourceware.org/autobook/autobook/autobook_91.html
	lt_current=3
	lt_revision=0
	lt_age=3
	LT_LDFLAGS="-version-info ${lt_current}:${lt_revision}:${lt_age} -no-undefined"

	m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])

	EXTRA_CPPFLAGS=
	EXTRA_CFLAGS=

	dnl check for -std=gnu11 compiler support (optional)
	dnl note that we don't just check if the compiler accepts '-std=x11'
	dnl but also that it supports the _Thread_local keyword because some compilers
	dnl (e.g. gcc 4.8) accept the command line option but do not implement TLS
	saved_CFLAGS="${CFLAGS}"
	CFLAGS="-std=gnu11"
	AC_MSG_CHECKING([if $CC supports -std=gnu11])
	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([_Thread_local int x;], [x = 42;])],
	[AC_MSG_RESULT([yes])
	c_dialect=gnu],
	[AC_MSG_RESULT([no])
	c_dialect=])
	if test "x$c_dialect" != xgnu; then
	dnl fallback check for -std=c11 compiler support (required)
	CFLAGS="-std=c11"
	AC_MSG_CHECKING([if $CC supports -std=c11])
	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([_Thread_local int x;], [x = 42;])],
	[AC_MSG_RESULT([yes])],
	[AC_MSG_RESULT([no])
	AC_MSG_ERROR([compiler with C11 support is required to build libusb])])
	c_dialect=c
	fi
	CFLAGS="${saved_CFLAGS}"

	AC_DEFINE([_GNU_SOURCE], [1], [Enable GNU extensions.])
	AC_DEFINE([DEFAULT_VISIBILITY], [__attribute__ ((visibility ("default")))], [Define to the attribute for default visibility.])
	AC_DEFINE([PRINTF_FORMAT(a, b)], [__attribute__ ((__format__ (__printf__, a, b)))], [Define to the attribute for enabling parameter checks on printf-like functions.])

	create_import_lib=
	is_android_linux=
	AC_MSG_CHECKING([operating system])
	case $host in
	-darwin)
	AC_MSG_RESULT([Darwin/Mac OS X])
	backend=darwin
	platform=posix
	;;
	-haiku)
	AC_MSG_RESULT([Haiku])
	backend=haiku
	platform=posix
	;;
	-linux \| -uclinux)
	dnl on Android Linux, some functions are in different places
	case $host in
	-linux-android)
	AC_MSG_RESULT([Android Linux])
	is_android_linux=yes
	;;
	*)
	AC_MSG_RESULT([Linux])
	;;
	esac
	backend=linux
	platform=posix
	;;
	-netbsd)
	AC_MSG_RESULT([NetBSD])
	backend=netbsd
	platform=posix
	;;
	-openbsd)
	AC_MSG_RESULT([OpenBSD])
	backend=openbsd
	platform=posix
	;;
	-solaris)
	AC_MSG_RESULT([SunOS])
	backend=sunos
	platform=posix
	;;
	-cygwin)
	AC_MSG_RESULT([Windows (using Cygwin)])
	backend=windows
	platform=windows
	EXTRA_CFLAGS="-mwin32"
	;;
	-mingw \| msys)
	AC_MSG_RESULT([Windows])
	backend=windows
	platform=windows
	test "x$enable_shared" = xyes && create_import_lib=yes
	EXTRA_CFLAGS="-mwin32 -fno-omit-frame-pointer"
	EXTRA_LDFLAGS="-static-libgcc"
	;;
	*)
	AC_MSG_RESULT([Null])
	AC_MSG_WARN([The host being compiled for is not supported.])
	AC_MSG_WARN([The library may compile but will not function in any useful manner.])
	backend=null
	platform=posix
	;;
	esac

	if test "x$platform" = xposix; then
	AC_DEFINE([PLATFORM_POSIX], [1], [Define to 1 if compiling for a POSIX platform.])
	AC_CHECK_TYPES([nfds_t], [], [], [[#include <poll.h>]])
	AC_CHECK_FUNCS([pipe2])
	dnl Some compilers do not support the '-pthread' option so check for it here
	saved_CFLAGS="${CFLAGS}"
	CFLAGS="-Wall -Werror -pthread"
	AC_MSG_CHECKING([if $CC recognizes -pthread])
	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
	[AC_MSG_RESULT([yes])
	AC_SUBST(THREAD_CFLAGS, [-pthread])],
	[AC_MSG_RESULT([no])])
	CFLAGS="${saved_CFLAGS}"
	dnl Android Linux and Darwin provide pthread functions directly in libc
	dnl glibc also provides some pthread functions directly, so search for a thread-specific function
	AC_SEARCH_LIBS([pthread_create], [pthread],
	[test "x$ac_cv_search_pthread_create" != "xnone required" && AC_SUBST(THREAD_LIBS, [-lpthread])],
	[], [])
	AC_SEARCH_LIBS([__atomic_fetch_add_4], [atomic])
	elif test "x$platform" = xwindows; then
	AC_DEFINE([PLATFORM_WINDOWS], [1], [Define to 1 if compiling for a Windows platform.])
	else
	AC_MSG_ERROR([Unknown platform])
	fi

	case $backend in
	darwin)
	AC_CHECK_FUNCS([pthread_threadid_np])
	LIBS="${LIBS} -lobjc -Wl,-framework,IOKit -Wl,-framework,CoreFoundation -Wl,-framework,Security"
	AC_CHECK_HEADERS([IOKit/usb/IOUSBHostFamilyDefinitions.h])
	;;
	haiku)
	LIBS="${LIBS} -lbe"
	;;
	linux)
	AC_SEARCH_LIBS([clock_gettime], [rt], [], [], [])
	AC_CHECK_FUNCS([pthread_setname_np])
	AC_ARG_ENABLE([udev],
	[AS_HELP_STRING([--enable-udev], [use udev for device enumeration and hotplug support (recommended) [default=yes]])],
	[use_udev=$enableval], [use_udev=yes])
	if test "x$use_udev" = xyes; then
	dnl system has udev. use it or fail!
	AC_CHECK_HEADER([libudev.h], [], [AC_MSG_ERROR([udev support requested but libudev header not installed])])
	AC_CHECK_LIB([udev], [udev_new], [], [AC_MSG_ERROR([udev support requested but libudev not installed])])

	# We can build umockdev tests (if available)
	PKG_PROG_PKG_CONFIG
	PKG_CHECK_MODULES(UMOCKDEV, umockdev-1.0 >= 0.16.0, ac_have_umockdev=yes, ac_have_umockdev=no)
	PKG_CHECK_MODULES(UMOCKDEV_HOTPLUG, umockdev-1.0 >= 0.17.7, ac_umockdev_hotplug=yes, ac_umockdev_hotplug=no)
	if test "x$ac_umockdev_hotplug" = xyes; then
	AC_DEFINE([UMOCKDEV_HOTPLUG], [1], [UMockdev hotplug code is not racy])
	fi
	else
	AC_CHECK_HEADERS([asm/types.h])
	AC_CHECK_HEADER([linux/netlink.h], [], [AC_MSG_ERROR([Linux netlink header not found])])
	AC_CHECK_HEADER([sys/socket.h], [], [AC_MSG_ERROR([Linux socket header not found])])
	fi
	;;
	sunos)
	LIBS="${LIBS} -ldevinfo"
	;;
	windows)
	AC_CHECK_TYPES([struct timespec], [], [], [[#include <time.h>]])
	AC_DEFINE([_WIN32_WINNT], [_WIN32_WINNT_VISTA], [Define to the oldest supported Windows version.])
	LT_LDFLAGS="${LT_LDFLAGS} -avoid-version -Wl,--add-stdcall-alias"
	;;
	*)
	dnl no special handling required
	;;
	esac

	dnl headers not available on all platforms but required on others
	AC_CHECK_HEADERS([sys/time.h])

	if test "x$platform" = xposix; then
	dnl check availability of clock_gettime()
	if test "x$backend" = xdarwin; then
	dnl need to verify that OS X target is 10.12 or later for clock_gettime()
	AC_MSG_CHECKING([whether OS X target version is 10.12 or later])
	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([
	#include <AvailabilityMacros.h>
	#if MAC_OS_X_VERSION_MIN_REQUIRED < 101200
	# error "Target OS X version is too old"
	#endif
	], [])],
	[AC_MSG_RESULT([yes])
	osx_10_12_or_later=yes],
	[AC_MSG_RESULT([no])
	osx_10_12_or_later=])
	if test "x$osx_10_12_or_later" = xyes; then
	AC_CHECK_FUNCS([clock_gettime], [have_clock_gettime=yes], [have_clock_gettime=])
	else
	AC_MSG_NOTICE([clock_gettime() is not available on target OS X version])
	fi
	else
	AC_CHECK_FUNCS([clock_gettime], [have_clock_gettime=yes], [AC_MSG_ERROR([clock_gettime() is required on this platform])])
	fi

	if test "x$have_clock_gettime" = xyes; then
	dnl the clock_gettime() function needs certain clock IDs defined
	AC_CHECK_DECL([CLOCK_MONOTONIC], [], [AC_MSG_ERROR([C library headers missing definition for CLOCK_MONOTONIC])], [[#include <time.h>]])
	dnl use the monotonic clock for condition variable timed waits if possible
	AC_CHECK_FUNCS([pthread_condattr_setclock], [need_clock_realtime=], [need_clock_realtime=yes])
	if test "x$need_clock_realtime" = xyes; then
	AC_CHECK_DECL([CLOCK_REALTIME], [], [AC_MSG_ERROR([C library headers missing definition for CLOCK_REALTIME])], [[#include <time.h>]])
	fi
	fi
	fi

	dnl eventfd support
	if test "x$backend" = xlinux \|\| test "x$backend" = xsunos; then
	AC_ARG_ENABLE([eventfd],
	[AS_HELP_STRING([--enable-eventfd], [use eventfd for signalling [default=auto]])],
	[use_eventfd=$enableval],
	[use_eventfd=auto])
	if test "x$use_eventfd" != xno; then
	AC_CHECK_HEADER([sys/eventfd.h], [eventfd_h=yes], [eventfd_h=])
	if test "x$eventfd_h" = xyes; then
	AC_CHECK_DECLS([EFD_NONBLOCK, EFD_CLOEXEC], [eventfd_h_ok=yes], [eventfd_h_ok=], [[#include <sys/eventfd.h>]])
	if test "x$eventfd_h_ok" = xyes; then
	AC_CHECK_FUNC([eventfd], [eventfd_ok=yes], [eventfd_ok=])
	if test "x$eventfd_ok" = xyes; then
	AC_DEFINE([HAVE_EVENTFD], [1], [Define to 1 if the system has eventfd functionality.])
	elif test "x$use_eventfd" = xyes; then
	AC_MSG_ERROR([eventfd() function not found; glibc 2.9+ required])
	fi
	elif test "x$use_eventfd" = xyes; then
	AC_MSG_ERROR([eventfd header not usable; glibc 2.9+ required])
	fi
	elif test "x$use_eventfd" = xyes; then
	AC_MSG_ERROR([eventfd header not available; glibc 2.9+ required])
	fi
	fi
	AC_MSG_CHECKING([whether to use eventfd for signalling])
	if test "x$use_eventfd" = xno; then
	AC_MSG_RESULT([no (disabled by user)])
	elif test "x$eventfd_h" != xyes; then
	AC_MSG_RESULT([no (header not available)])
	elif test "x$eventfd_h_ok" != xyes; then
	AC_MSG_RESULT([no (header not usable)])
	elif test "x$eventfd_ok" != xyes; then
	AC_MSG_RESULT([no (functions not available)])
	else
	AC_MSG_RESULT([yes])
	fi
	fi

	dnl timerfd support
	if test "x$backend" = xlinux \|\| test "x$backend" = xsunos; then
	AC_ARG_ENABLE([timerfd],
	[AS_HELP_STRING([--enable-timerfd], [use timerfd for timing [default=auto]])],
	[use_timerfd=$enableval],
	[use_timerfd=auto])
	if test "x$use_timerfd" != xno; then
	AC_CHECK_HEADER([sys/timerfd.h], [timerfd_h=yes], [timerfd_h=])
	if test "x$timerfd_h" = xyes; then
	AC_CHECK_DECLS([TFD_NONBLOCK, TFD_CLOEXEC], [timerfd_h_ok=yes], [timerfd_h_ok=], [[#include <sys/timerfd.h>]])
	if test "x$timerfd_h_ok" = xyes; then
	AC_CHECK_FUNC([timerfd_create], [timerfd_ok=yes], [timerfd_ok=])
	if test "x$timerfd_ok" = xyes; then
	AC_DEFINE([HAVE_TIMERFD], [1], [Define to 1 if the system has timerfd functionality.])
	elif test "x$use_timerfd" = xyes; then
	AC_MSG_ERROR([timerfd_create() function not found; glibc 2.9+ required])
	fi
	elif test "x$use_timerfd" = xyes; then
	AC_MSG_ERROR([timerfd header not usable; glibc 2.9+ required])
	fi
	elif test "x$use_timerfd" = xyes; then
	AC_MSG_ERROR([timerfd header not available; glibc 2.9+ required])
	fi
	fi
	AC_MSG_CHECKING([whether to use timerfd for timing])
	if test "x$use_timerfd" = xno; then
	AC_MSG_RESULT([no (disabled by user)])
	elif test "x$timerfd_h" != xyes; then
	AC_MSG_RESULT([no (header not available)])
	elif test "x$timerfd_h_ok" != xyes; then
	AC_MSG_RESULT([no (header not usable)])
	elif test "x$timerfd_ok" != xyes; then
	AC_MSG_RESULT([no (functions not available)])
	else
	AC_MSG_RESULT([yes])
	fi
	fi

	dnl Message logging
	AC_ARG_ENABLE([log],
	[AS_HELP_STRING([--disable-log], [disable all logging])],
	[log_enabled=$enableval],
	[log_enabled=yes])
	if test "x$log_enabled" != xno; then
	AC_DEFINE([ENABLE_LOGGING], [1], [Define to 1 to enable message logging.])
	fi

	AC_ARG_ENABLE([debug-log],
	[AS_HELP_STRING([--enable-debug-log], [start with debug message logging enabled [default=no]])],
	[debug_log_enabled=$enableval],
	[debug_log_enabled=no])
	if test "x$debug_log_enabled" != xno; then
	AC_DEFINE([ENABLE_DEBUG_LOGGING], [1], [Define to 1 to start with debug message logging enabled.])
	fi

	AC_ARG_ENABLE([system-log],
	[AS_HELP_STRING([--enable-system-log], [output logging messages to the systemwide log, if supported by the OS [default=no]])],
	[system_log_enabled=$enableval],
	[system_log_enabled=no])
	if test "x$system_log_enabled" != xno; then
	AC_DEFINE([USE_SYSTEM_LOGGING_FACILITY], [1], [Define to 1 to output logging messages to the systemwide log.])
	if test "x$backend" != xwindows && test "x$is_android_linux" != xyes; then
	dnl Check if syslog is available in standard C library
	AC_CHECK_HEADER([syslog.h], [syslog_h=yes], [syslog_h=])
	if test "x$syslog_h" = xyes; then
	AC_CHECK_FUNCS([syslog])
	fi
	fi
	fi

	dnl Examples build
	AC_ARG_ENABLE([examples-build],
	[AS_HELP_STRING([--enable-examples-build], [build example applications [default=no]])],
	[build_examples=$enableval],
	[build_examples=no])

	dnl Tests build
	AC_ARG_ENABLE([tests-build],
	[AS_HELP_STRING([--enable-tests-build], [build test applications [default=no]])],
	[build_tests=$enableval],
	[build_tests=no])

	AM_CONDITIONAL([BUILD_EXAMPLES], [test "x$build_examples" != xno])
	AM_CONDITIONAL([BUILD_TESTS], [test "x$build_tests" != xno])
	AM_CONDITIONAL([BUILD_UMOCKDEV_TEST], [test "x$ac_have_umockdev" = xyes -a "x$log_enabled" != xno])
	AM_CONDITIONAL([CREATE_IMPORT_LIB], [test "x$create_import_lib" = xyes])
	AM_CONDITIONAL([OS_DARWIN], [test "x$backend" = xdarwin])
	AM_CONDITIONAL([OS_HAIKU], [test "x$backend" = xhaiku])
	AM_CONDITIONAL([OS_LINUX], [test "x$backend" = xlinux])
	AM_CONDITIONAL([OS_NETBSD], [test "x$backend" = xnetbsd])
	AM_CONDITIONAL([OS_NULL], [test "x$backend" = xnull])
	AM_CONDITIONAL([OS_OPENBSD], [test "x$backend" = xopenbsd])
	AM_CONDITIONAL([OS_SUNOS], [test "x$backend" = xsunos])
	AM_CONDITIONAL([OS_WINDOWS], [test "x$backend" = xwindows])
	AM_CONDITIONAL([PLATFORM_POSIX], [test "x$platform" = xposix])
	AM_CONDITIONAL([PLATFORM_WINDOWS], [test "x$platform" = xwindows])
	AM_CONDITIONAL([USE_UDEV], [test "x$use_udev" = xyes])

	dnl The -Wcast-function-type warning causes a flurry of warnings when compiling
	dnl Windows with GCC 8 or later because of dynamically loaded functions
	if test "x$backend" = xwindows; then
	saved_CFLAGS="${CFLAGS}"
	CFLAGS="-Werror -Wcast-function-type"
	AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], [])],
	[EXTRA_CFLAGS="${EXTRA_CFLAGS} -Wno-cast-function-type"],
	[])
	CFLAGS="${saved_CFLAGS}"
	fi

	SHARED_CFLAGS="-Wall -Wextra -Wshadow -Wunused -Wwrite-strings -Werror=format-security -Werror=implicit-function-declaration -Werror=implicit-int -Werror=init-self -Werror=missing-prototypes -Werror=strict-prototypes -Werror=undef -Werror=uninitialized"

	AM_CPPFLAGS="${EXTRA_CPPFLAGS}"
	AC_SUBST(AM_CPPFLAGS)

	AM_CFLAGS="-std=${c_dialect}11 ${EXTRA_CFLAGS} ${SHARED_CFLAGS}"
	AC_SUBST(AM_CFLAGS)

	AM_CXXFLAGS="-std=${c_dialect}++11 ${EXTRA_CFLAGS} ${SHARED_CFLAGS} -Wmissing-declarations"
	AC_SUBST(AM_CXXFLAGS)

	AC_SUBST(LT_LDFLAGS)

	AC_SUBST([EXTRA_LDFLAGS])

	dnl set name of html output directory for doxygen
	AC_SUBST(DOXYGEN_HTMLDIR, [api-1.0])

	AC_CONFIG_FILES([libusb-1.0.pc])
	AC_CONFIG_FILES([Makefile])
	AC_CONFIG_FILES([libusb/Makefile])
	AC_CONFIG_FILES([examples/Makefile])
	AC_CONFIG_FILES([tests/Makefile])
	AC_CONFIG_FILES([doc/Makefile])
	AC_CONFIG_FILES([doc/doxygen.cfg])
	AC_OUTPUT