build: Require C11 to build and clean up autoconfig/automake files

C11 compiler support has been available for many years now. It is not
unreasonable to require this now, and doing so allows some cleanup to
the configure script. It is no longer necessary to check for compiler
support of the '-fvibility' flag because any compiler that supports C11
will support this flag as well.

Fix up the way that compiler and linker flags are passed down to the
various makefiles. The compiler flags should be shared by all, but the
linker flags and libraries should be separated between the library and
the examples/tests. The visibility flag is only relevant for the
library and the thread flags are only relevant for sources using thread
constructs, so provide them as needed.

Rearrange configure.ac to group similar functionality and consolidate
where possible.

Based on these changes, update the Travis configuration file to include
newer versions of test platforms to ensure proper C11 compiler support.

Signed-off-by: Chris Dickens <christopher.a.dickens@gmail.com>

13 files changed, 189 insertions, 208 deletions

diff --git a/.travis.yml b/.travis.yml
index f5d194a..eb477a1 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,30 +3,34 @@ language: c
 matrix:
     include:
         - os: linux
-          dist: trusty
-          sudo: required
+          dist: bionic
           compiler: gcc
         - os: linux
-          dist: trusty
-          sudo: required
+          dist: bionic
+          compiler: clang
+        - os: linux
+          dist: xenial
+          compiler: gcc
+        - os: linux
+          dist: xenial
           compiler: clang
         - os: osx
-          osx_image: xcode8
+          osx_image: xcode11.3
           compiler: gcc
         - os: osx
-          osx_image: xcode8
+          osx_image: xcode11.3
           compiler: clang
         - os: osx
-          osx_image: xcode7.1
+          osx_image: xcode9.4
           compiler: gcc
         - os: osx
-          osx_image: xcode7.1
+          osx_image: xcode9.4
           compiler: clang
         - os: osx
-          osx_image: beta-xcode6.2
+          osx_image: xcode6.4
           compiler: gcc
         - os: osx
-          osx_image: beta-xcode6.2
+          osx_image: xcode6.4
           compiler: clang
 
 addons:
diff --git a/Xcode/common.xcconfig b/Xcode/common.xcconfig
index 2c7ff3c..0989351 100644
--- a/Xcode/common.xcconfig
+++ b/Xcode/common.xcconfig
@@ -17,11 +17,11 @@
 // License along with this library; if not, write to the Free Software
 // Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
-// libusb does not follow C99 strict aliasing rules, so disable it.
+// libusb does not follow C11 strict aliasing rules, so disable it.
 GCC_STRICT_ALIASING = NO
 
-// Use C99 dialect.
-GCC_C_LANGUAGE_STANDARD = c99
+// Use GNU11 dialect.
+GCC_C_LANGUAGE_STANDARD = gnu11
 
 // Don't search user paths with <> style #includes.
 ALWAYS_SEARCH_USER_PATHS = NO
diff --git a/Xcode/config.h b/Xcode/config.h
index 3aaeb7b..9761542 100644
--- a/Xcode/config.h
+++ b/Xcode/config.h
@@ -2,15 +2,12 @@
 
 #include <AvailabilityMacros.h>
 
-/* Default visibility */
+/* Define to the attribute for default visibility. */
 #define DEFAULT_VISIBILITY /**/
 
-/* Message logging */
+/* Define to 1 to enable message logging. */
 #define ENABLE_LOGGING 1
 
-/* Define to 1 if the compiler supports _Thread_local. */
-#define HAVE_CC_THREAD_LOCAL 1
-
 /* On 10.12 and later, use newly available clock_*() functions */
 #if MAC_OS_X_VERSION_MIN_REQUIRED >= 101200
 /* Define to 1 if you have the `clock_gettime' function. */
@@ -29,11 +26,11 @@
 /* Define to 1 if you have the <sys/time.h> header file. */
 #define HAVE_SYS_TIME_H 1
 
-/* Use POSIX poll() implementation */
+/* Define to 1 if using the POSIX poll() implementation. */
 #define POLL_POSIX 1
 
-/* Use POSIX Threads */
+/* Define to 1 if using POSIX threads. */
 #define THREADS_POSIX 1
 
-/* Use GNU extensions */
+/* Enable GNU extensions. */
 #define _GNU_SOURCE 1
diff --git a/android/config.h b/android/config.h
index 59c7544..341c01f 100644
--- a/android/config.h
+++ b/android/config.h
@@ -17,20 +17,20 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  */
 
-/* Default visibility */
-#define DEFAULT_VISIBILITY __attribute__((visibility("default")))
+/* Define to the attribute for default visibility. */
+#define DEFAULT_VISIBILITY __attribute__ ((visibility ("default")))
 
-/* Start with debug message logging enabled */
+/* Define to 1 to start with debug message logging enabled. */
 /* #undef ENABLE_DEBUG_LOGGING */
 
-/* Message logging */
-#define ENABLE_LOGGING
+/* Define to 1 to enable message logging. */
+#define ENABLE_LOGGING 1
 
 /* Define to 1 if you have the <asm/types.h> header file. */
 #define HAVE_ASM_TYPES_H 1
 
-/* Define to 1 if the compiler supports _Thread_local. */
-#define HAVE_CC_THREAD_LOCAL 1
+/* Define to 1 if you have the `clock_gettime' function. */
+#define HAVE_CLOCK_GETTIME 1
 
 /* Define to 1 if the system has the type `nfds_t'. */
 #define HAVE_NFDS_T 1
@@ -41,11 +41,14 @@
 /* Define to 1 if you have the <sys/time.h> header file. */
 #define HAVE_SYS_TIME_H 1
 
-/* Use POSIX poll() implementation */
+/* Define to 1 if using the POSIX poll() implementation. */
 #define POLL_POSIX 1
 
-/* Use POSIX Threads */
+/* Define to 1 if using POSIX threads. */
 #define THREADS_POSIX 1
 
-/* Enable output to system log */
+/* Define to 1 to output logging messages to the systemwide log. */
 #define USE_SYSTEM_LOGGING_FACILITY 1
+
+/* Enable GNU extensions. */
+#define _GNU_SOURCE 1
diff --git a/configure.ac b/configure.ac
index 37c79c9..2d6cfad 100644
--- a/configure.ac
+++ b/configure.ac
@@ -15,7 +15,17 @@ 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:
@@ -24,26 +34,44 @@ dnl http://sourceware.org/autobook/autobook/autobook_91.html
 lt_current=2
 lt_revision=0
 lt_age=2
-LTLDFLAGS="-version-info ${lt_current}:${lt_revision}:${lt_age}"
-
-AM_INIT_AUTOMAKE
+LT_LDFLAGS="-version-info ${lt_current}:${lt_revision}:${lt_age} -no-undefined"
 
-AC_CONFIG_SRCDIR([libusb/core.c])
-AC_CONFIG_MACRO_DIR([m4])
-AC_CONFIG_HEADERS([config.h])
 m4_ifdef([AM_SILENT_RULES],[AM_SILENT_RULES([yes])])
 
-AC_PREREQ([2.69])
-AC_PROG_CC
-AC_PROG_CXX
-LT_INIT
-LT_LANG([Windows Resource])
-AC_C_INLINE
-AM_PROG_CC_C_O
-AC_DEFINE([_GNU_SOURCE], [1], [Use GNU extensions])
+dnl check for -std=gnu11 compiler support (optional)
+dnl note that we don't just check whether 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="${CFLAGS}"
+CFLAGS="-std=gnu11"
+AC_MSG_CHECKING([whether CC supports -std=gnu11])
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([_Thread_local int x;], [x = 42;])],
+	[AC_MSG_RESULT([yes])
+	 cc_supports_gnu11=yes],
+	[AC_MSG_RESULT([no])
+	 cc_supports_gnu11=])
+CFLAGS="${saved_CFLAGS}"
+
+if test "x$cc_supports_gnu11" = xyes; then
+	AM_CFLAGS="-std=gnu11"
+else
+	dnl fallback check for -std=c11 compiler support (required)
+	saved_CFLAGS="${CFLAGS}"
+	CFLAGS="-std=c11"
+	AC_MSG_CHECKING([whether 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])])
+	CFLAGS="${saved_CFLAGS}"
+	AM_CFLAGS="-std=c11"
+fi
 
-LTLDFLAGS="${LTLDFLAGS} -no-undefined"
+AC_DEFINE([_GNU_SOURCE], [1], [Enable GNU extensions.])
+AC_DEFINE([DEFAULT_VISIBILITY], [__attribute__ ((visibility ("default")))], [Define to the attribute for default visibility.])
 
+create_import_lib=
+is_android_linux=
 AC_MSG_CHECKING([operating system])
 case $host in
 *-darwin*)
@@ -59,15 +87,14 @@ case $host in
 	threads=posix
 	;;
 *-linux* | *-uclinux*)
-	dnl on linux-android platform, some functions are in different places
+	dnl on Android Linux, some functions are in different places
 	case $host in
 	*-linux-android*)
-		AC_MSG_RESULT([Linux (Android system)])
-		is_backend_android=yes
+		AC_MSG_RESULT([Android Linux])
+		is_android_linux=yes
 		;;
 	*)
 		AC_MSG_RESULT([Linux])
-		is_backend_android=no
 		;;
 	esac
 	backend=linux
@@ -108,27 +135,51 @@ case $host in
 	;;
 *)
 	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"
 	poll=posix
 	threads="posix"
 	;;
 esac
 
+if test "x$poll" = xposix; then
+	AC_DEFINE([POLL_POSIX], [1], [Define to 1 if using the POSIX poll() implementation.])
+	AC_CHECK_TYPES([nfds_t], [], [], [[#include <poll.h>]])
+	AC_CHECK_FUNCS([pipe2])
+elif test "x$poll" = xwindows; then
+	AC_DEFINE([POLL_WINDOWS], [1], [Define to 1 if using the Windows poll() implementation.])
+else
+	AC_MSG_ERROR([Unknown poll implementation])
+fi
+
+if test "x$threads" = xposix; then
+	AC_DEFINE([THREADS_POSIX], [1], [Define to 1 if using POSIX threads.])
+	AC_SUBST(THREAD_CFLAGS, [-pthread])
+	dnl Android Linux and Darwin provide pthread functions directly in libc
+	dnl glibc also provides some pthread functions directly, so search for a thread-specific function
+	AC_SEARCH_LIBS([pthread_key_create], [pthread], [AC_SUBST(THREAD_LIBS, [-lpthread])], [], [])
+elif test "x$threads" = xwindows; then
+	AC_DEFINE([THREADS_WINDOWS], [1], [Define to 1 if using Windows threads.])
+else
+	AC_MSG_ERROR([Unknown threads implementation])
+fi
+
 case $backend in
 darwin)
 	AC_CHECK_FUNCS([pthread_threadid_np])
-	LIBS="-lobjc -Wl,-framework,IOKit -Wl,-framework,CoreFoundation"
-	LTLDFLAGS="${LTLDFLAGS} -Wl,-prebind"
+	LIBS="${LIBS} -lobjc -Wl,-framework,IOKit -Wl,-framework,CoreFoundation"
 	;;
 haiku)
-	LIBS="-lbe"
+	LIBS="${LIBS} -lbe"
 	;;
 linux)
-	AC_SEARCH_LIBS([clock_gettime], [rt], [], [], [-pthread])
+	AC_SEARCH_LIBS([clock_gettime], [rt], [], [], [])
+	AC_CHECK_FUNCS([pthread_setname_np])
 	AC_ARG_ENABLE([udev],
 		[AC_HELP_STRING([--enable-udev], [use udev for device enumeration and hotplug support (recommended) [default=yes]])],
-		[], [enable_udev=yes])
-	if test "x$enable_udev" = xyes ; then
+		[use_udev=$enableval], [use_udev=yes])
+	if test "x$use_udev" = xyes; then
 		dnl system has udev. use it or fail!
 		AC_CHECK_HEADER([libudev.h], [], [AC_MSG_ERROR([udev support requested but libudev header not installed])])
 		AC_CHECK_LIB([udev], [udev_new], [], [AC_MSG_ERROR([udev support requested but libudev not installed])])
@@ -137,84 +188,30 @@ linux)
 		AC_CHECK_HEADER([linux/netlink.h], [], [AC_MSG_ERROR([Linux netlink header not found])])
 		AC_CHECK_HEADER([sys/socket.h], [], [AC_MSG_ERROR([Linux socket header not found])])
 	fi
-	if test "x$is_backend_android" != xyes; then
-		THREAD_CFLAGS="-pthread"
-		LIBS="${LIBS} -pthread"
-	fi
-	AC_CHECK_FUNCS([pthread_setname_np])
-	;;
-netbsd)
-	THREAD_CFLAGS="-pthread"
-	LIBS="-pthread"
-	;;
-null)
-	THREAD_CFLAGS="-pthread"
-	LIBS="-pthread"
-	;;
-openbsd)
-	THREAD_CFLAGS="-pthread"
-	LIBS="-pthread"
 	;;
 sunos)
-	THREAD_CFLAGS="-pthread"
-	LIBS="-pthread -ldevinfo"
+	LIBS="${LIBS} -ldevinfo"
 	;;
 windows)
 	AC_CHECK_TYPES([struct timespec], [], [], [[#include <time.h>]])
-	LIBS=""
-	LTLDFLAGS="${LTLDFLAGS} -avoid-version -Wl,--add-stdcall-alias"
-	AC_DEFINE([_WIN32_WINNT], [_WIN32_WINNT_VISTA], [Oldest Windows version supported (Vista)])
+	AC_DEFINE([_WIN32_WINNT], [_WIN32_WINNT_VISTA], [Define to the oldest supported Windows version.])
+	LT_LDFLAGS="${LT_LDFLAGS} -avoid-version -Wl,--add-stdcall-alias"
 	;;
 *)
-	AC_MSG_ERROR([Unknown backend])
+	dnl no special handling required
 	;;
 esac
 
-AC_SUBST(LIBS)
-
-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([POLL_POSIX], [test "x$poll" = xposix])
-AM_CONDITIONAL([POLL_WINDOWS], [test "x$poll" = xwindows])
-AM_CONDITIONAL([THREADS_POSIX], [test "x$threads" = xposix])
-AM_CONDITIONAL([THREADS_WINDOWS], [test "x$threads" = xwindows])
-AM_CONDITIONAL([CREATE_IMPORT_LIB], [test "x$create_import_lib" = xyes])
-AM_CONDITIONAL([USE_UDEV], [test "x$enable_udev" = xyes])
-
-if test "x$poll" = xposix; then
-	AC_DEFINE([POLL_POSIX], [1], [Use POSIX poll() implementation])
-	AC_CHECK_TYPES([nfds_t], [], [], [[#include <poll.h>]])
-	AC_CHECK_FUNCS([pipe2])
-elif test "x$poll" = xwindows; then
-	AC_DEFINE([POLL_WINDOWS], [1], [Use Windows poll() implementation])
-else
-	AC_MSG_ERROR([Unknown poll implementation])
-fi
-
-if test "x$threads" = xposix; then
-	AC_DEFINE([THREADS_POSIX], [1], [Use POSIX Threads])
-elif test "x$threads" = xwindows; then
-	AC_DEFINE([THREADS_WINDOWS], [1], [Use Windows Threads])
-else
-	AC_MSG_ERROR([Unknown threads implementation])
-fi
-
 dnl headers not available on all platforms but required on others
 AC_CHECK_HEADERS([sys/time.h])
 
 dnl the clock_gettime() function needs certain clock IDs defined
-AC_CHECK_FUNCS([clock_gettime], [have_clock_gettime=yes], [have_clockgettime=no])
+AC_CHECK_FUNCS([clock_gettime], [have_clock_gettime=yes], [have_clock_gettime=])
 if test "x$have_clock_gettime" = xyes; then
 	AC_CHECK_DECL([CLOCK_REALTIME], [], [AC_MSG_ERROR([C library headers missing definition for CLOCK_REALTIME])], [[#include <time.h>]])
 	AC_CHECK_DECL([CLOCK_MONOTONIC], [], [AC_MSG_ERROR([C library headers missing definition for CLOCK_MONOTONIC])], [[#include <time.h>]])
 elif test "x$backend" != xdarwin && test "x$backend" != xwindows; then
-       AC_MSG_ERROR([clock_gettime() is required on this platform])
+	AC_MSG_ERROR([clock_gettime() is required on this platform])
 fi
 
 dnl timerfd support
@@ -224,13 +221,13 @@ if test "x$backend" = xlinux || test "x$backend" = xsunos; then
 		[use_timerfd=$enableval],
 		[use_timerfd=auto])
 	if test "x$use_timerfd" != xno; then
-		AC_CHECK_HEADER([sys/timerfd.h], [timerfd_h=yes], [timerfd_h=no])
+		AC_CHECK_HEADER([sys/timerfd.h], [timerfd_h=yes], [timerfd_h=])
 		if test "x$timerfd_h" = xyes; then
-			AC_CHECK_DECLS([TFD_NONBLOCK, TFD_CLOEXEC], [timerfd_h_ok=yes], [timerfd_h_ok=no], [[#include <sys/timerfd.h>]])
+			AC_CHECK_DECLS([TFD_NONBLOCK, TFD_CLOEXEC], [timerfd_h_ok=yes], [timerfd_h_ok=], [[#include <sys/timerfd.h>]])
 			if test "x$timerfd_h_ok" = xyes; then
-				AC_CHECK_FUNC([timerfd_create], [timerfd_ok=yes], [timerfd_ok=no])
+				AC_CHECK_FUNC([timerfd_create], [timerfd_ok=yes], [timerfd_ok=])
 				if test "x$timerfd_ok" = xyes; then
-					AC_DEFINE([HAVE_TIMERFD], [1], [Define if the system has timerfd functionality])
+					AC_DEFINE([HAVE_TIMERFD], [1], [Define to 1 if the system has timerfd functionality.])
 				elif test "x$use_timerfd" = xyes; then
 					AC_MSG_ERROR([timerfd_create() function not found; glibc 2.9+ required])
 				fi
@@ -244,11 +241,11 @@ if test "x$backend" = xlinux || test "x$backend" = xsunos; then
 	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" = xno; then
-		AC_MSG_RESULT([no (header not usable)])
-	elif test "x$timerfd_h_ok" = xno; then
+	elif test "x$timerfd_h" != xyes; then
 		AC_MSG_RESULT([no (header not available)])
-	elif test "x$timerfd_ok" = xno; then
+	elif test "x$timerfd_h_ok" != xyes; then
+		AC_MSG_RESULT([no (header not usable)])
+	elif test "x$timerfd_ok" != xyes; then
 		AC_MSG_RESULT([no (functions not available)])
 	else
 		AC_MSG_RESULT([yes])
@@ -261,7 +258,7 @@ AC_ARG_ENABLE([log],
 	[log_enabled=$enableval],
 	[log_enabled=yes])
 if test "x$log_enabled" != xno; then
-	AC_DEFINE([ENABLE_LOGGING], [1], [Message logging])
+	AC_DEFINE([ENABLE_LOGGING], [1], [Define to 1 to enable message logging.])
 fi
 
 AC_ARG_ENABLE([debug-log],
@@ -269,18 +266,18 @@ AC_ARG_ENABLE([debug-log],
 	[debug_log_enabled=$enableval],
 	[debug_log_enabled=no])
 if test "x$debug_log_enabled" != xno; then
-	AC_DEFINE([ENABLE_DEBUG_LOGGING], [1], [Start with debug message logging enabled])
+	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 system wide log, if supported by the OS [default=no]])],
+	[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], [Enable output to system log])
-	if test "x$backend" != xwindows && test "x$is_backend_android" != xyes; 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=no])
+		AC_CHECK_HEADER([syslog.h], [syslog_h=yes], [syslog_h=])
 		if test "x$syslog_h" = xyes; then
 			AC_CHECK_FUNCS([syslog])
 		fi
@@ -292,69 +289,42 @@ AC_ARG_ENABLE([examples-build],
 	[AS_HELP_STRING([--enable-examples-build], [build example applications [default=no]])],
 	[build_examples=$enableval],
 	[build_examples=no])
-AM_CONDITIONAL([BUILD_EXAMPLES], [test "x$build_examples" != xno])
+if test "x$build_examples" != xno; then
+	dnl sigaction needed for some example programs
+	AC_CHECK_FUNC([sigaction], [have_sigaction=yes], [have_sigaction=])
+fi
 
 dnl Tests build
 AC_ARG_ENABLE([tests-build],
 	[AS_HELP_STRING([--enable-tests-build], [build test applications [default=no]])],
 	[build_tests=$enableval],
 	[build_tests=no])
-AM_CONDITIONAL([BUILD_TESTS], [test "x$build_tests" != xno])
 
-dnl sigaction needed for some example programs
-if test "x$build_examples" != xno; then
-	AC_CHECK_FUNC([sigaction], [have_sigaction=yes], [have_sigaction=no])
-fi
+AM_CONDITIONAL([BUILD_EXAMPLES], [test "x$build_examples" != xno])
+AM_CONDITIONAL([BUILD_TESTS], [test "x$build_tests" != xno])
+AM_CONDITIONAL([CREATE_IMPORT_LIB], [test "x$create_import_lib" = xyes])
 AM_CONDITIONAL([HAVE_SIGACTION], [test "x$have_sigaction" = xyes])
+AM_CONDITIONAL([OS_DARWIN], [test "x$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$backend" = xwindows])
+AM_CONDITIONAL([POLL_POSIX], [test "x$poll" = xposix])
+AM_CONDITIONAL([POLL_WINDOWS], [test "x$poll" = xwindows])
+AM_CONDITIONAL([THREADS_POSIX], [test "x$threads" = xposix])
+AM_CONDITIONAL([THREADS_WINDOWS], [test "x$threads" = xwindows])
+AM_CONDITIONAL([USE_UDEV], [test "x$use_udev" = xyes])
 
-dnl check for -fvisibility=hidden compiler support (GCC >= 3.4)
-saved_CFLAGS="${CFLAGS}"
-dnl -Werror required for cygwin
-CFLAGS="${CFLAGS} -Werror -fvisibility=hidden"
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
-	[VISIBILITY_CFLAGS="-fvisibility=hidden"
-	 AC_DEFINE([DEFAULT_VISIBILITY], [__attribute__((visibility("default")))], [Default visibility])],
-	[VISIBILITY_CFLAGS=""
-	 AC_DEFINE([DEFAULT_VISIBILITY], [], [Default visibility])],
-	])
-CFLAGS="${saved_CFLAGS}"
-
-dnl check for -Wno-pointer-sign compiler support (GCC >= 4)
-saved_CFLAGS="${CFLAGS}"
-CFLAGS="${CFLAGS} -Wno-pointer-sign"
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
-	nopointersign_cflags="-Wno-pointer-sign", nopointersign_cflags="")
-CFLAGS="${saved_CFLAGS}"
-
-dnl check for -std=gnu11 compiler support
-saved_CFLAGS="${CFLAGS}"
-CFLAGS="-std=gnu11"
-AC_MSG_CHECKING([whether CC supports -std=gnu11])
-AC_COMPILE_IFELSE([AC_LANG_PROGRAM([])],
-	[AC_MSG_RESULT([yes])
-	 AM_CFLAGS="${AM_CFLAGS} -std=gnu11"],
-	[AC_MSG_RESULT([no])])
-CFLAGS="${saved_CFLAGS}"
-
-dnl check for _Thread_local compiler support
-if test "x$backend" != xwindows; then
-	saved_CFLAGS="${CFLAGS}"
-	saved_LDFLAGS="${LDFLAGS}"
-	CFLAGS="${CFLAGS} -fPIC"
-	LDFLAGS="${LDFLAGS} -shared"
-	AC_MSG_CHECKING([whether CC supports _Thread_local])
-	AC_LINK_IFELSE([AC_LANG_PROGRAM([], [static _Thread_local int v])],
-		[AC_MSG_RESULT([yes])
-		 AC_DEFINE([HAVE_CC_THREAD_LOCAL], [1], [Define to 1 if the compiler supports _Thread_local.])],
-		[AC_MSG_RESULT([no])])
-	CFLAGS="${saved_CFLAGS}"
-	LDFLAGS="${saved_LDFLAGS}"
-fi
+AM_CFLAGS="${AM_CFLAGS} -Wall -Wshadow -Wstrict-prototypes -Wundef -Wunused -Werror=implicit-function-declaration"
+AC_SUBST(AM_CFLAGS)
 
-AM_CFLAGS="${AM_CFLAGS} -Wall -Wundef -Wunused -Wstrict-prototypes -Werror-implicit-function-declaration ${nopointersign_cflags} -Wshadow ${THREAD_CFLAGS} ${VISIBILITY_CFLAGS}"
+AM_CXXFLAGS="${AM_CFLAGS}"
+AC_SUBST(AM_CXXFLAGS)
 
-AC_SUBST(AM_CFLAGS)
-AC_SUBST(LTLDFLAGS)
+AC_SUBST(LT_LDFLAGS)
 
 dnl set name of html output directory for doxygen
 AC_SUBST(DOXYGEN_HTMLDIR, [api-1.0])
diff --git a/examples/Makefile.am b/examples/Makefile.am
index 6185d00..2658490 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -1,19 +1,18 @@
 AM_CPPFLAGS = -I$(top_srcdir)/libusb
 LDADD = ../libusb/libusb-1.0.la
+LIBS =
 
-noinst_PROGRAMS = listdevs xusb fxload hotplugtest testlibusb
+noinst_PROGRAMS = fxload hotplugtest listdevs testlibusb xusb
+
+fxload_SOURCES = ezusb.c ezusb.h fxload.c
 
 if HAVE_SIGACTION
 noinst_PROGRAMS += dpfp
-
 if THREADS_POSIX
-dpfp_threaded_CFLAGS = $(AM_CFLAGS)
 noinst_PROGRAMS += dpfp_threaded
+dpfp_threaded_CFLAGS = $(AM_CFLAGS) $(THREAD_CFLAGS)
+dpfp_threaded_LDADD = $(LDADD) $(THREAD_LIBS)
 endif
 
-sam3u_benchmark_SOURCES = sam3u_benchmark.c
 noinst_PROGRAMS += sam3u_benchmark
 endif
-
-fxload_SOURCES = ezusb.c ezusb.h fxload.c
-fxload_CFLAGS = $(THREAD_CFLAGS) $(AM_CFLAGS)
diff --git a/examples/testlibusb.c b/examples/testlibusb.c
index a6bb15a..8031e75 100755
--- a/examples/testlibusb.c
+++ b/examples/testlibusb.c
@@ -164,7 +164,7 @@ static void print_device(libusb_device *dev)
 {
 	struct libusb_device_descriptor desc;
 	libusb_device_handle *handle = NULL;
-	char string[256];
+	unsigned char string[256];
 	int ret;
 	uint8_t i;
 
@@ -183,19 +183,19 @@ static void print_device(libusb_device *dev)
 		if (desc.iManufacturer) {
 			ret = libusb_get_string_descriptor_ascii(handle, desc.iManufacturer, string, sizeof(string));
 			if (ret > 0)
-				printf("  Manufacturer:              %s\n", string);
+				printf("  Manufacturer:              %s\n", (char *)string);
 		}
 
 		if (desc.iProduct) {
 			ret = libusb_get_string_descriptor_ascii(handle, desc.iProduct, string, sizeof(string));
 			if (ret > 0)
-				printf("  Product:                   %s\n", string);
+				printf("  Product:                   %s\n", (char *)string);
 		}
 
 		if (desc.iSerialNumber && verbose) {
 			ret = libusb_get_string_descriptor_ascii(handle, desc.iSerialNumber, string, sizeof(string));
 			if (ret > 0)
-				printf("  Serial Number:             %s\n", string);
+				printf("  Serial Number:             %s\n", (char *)string);
 		}
 	}
 
diff --git a/libusb/Makefile.am b/libusb/Makefile.am
index ad6e8ab..8b89ee6 100644
--- a/libusb/Makefile.am
+++ b/libusb/Makefile.am
@@ -1,5 +1,9 @@
 AUTOMAKE_OPTIONS = subdir-objects
 
+AM_CFLAGS += -fvisibility=hidden $(THREAD_CFLAGS)
+AM_CXXFLAGS += -fvisibility=hidden $(THREAD_CFLAGS)
+AM_LDFLAGS = $(LT_LDFLAGS)
+
 lib_LTLIBRARIES = libusb-1.0.la
 
 POSIX_POLL_SRC = os/poll_posix.h os/poll_posix.c
@@ -35,7 +39,6 @@ OS_WINDOWS_SRC = libusb-1.0.def libusb-1.0.rc \
 
 if OS_DARWIN
 OS_SRC = $(OS_DARWIN_SRC)
-AM_CFLAGS_EXT = -no-cpp-precomp
 endif
 
 if OS_HAIKU
@@ -85,7 +88,6 @@ all-local: .libs/libusb-1.0.dll.a
 endif
 endif
 
-libusb_1_0_la_LDFLAGS = $(LTLDFLAGS)
 libusb_1_0_la_SOURCES = libusbi.h version.h version_nano.h \
 	core.c descriptor.c hotplug.h hotplug.c io.c strerror.c sync.c \
 	$(POLL_SRC) $(THREADS_SRC) $(OS_SRC)
diff --git a/libusb/libusbi.h b/libusb/libusbi.h
index 1a5528d..9eeb920 100644
--- a/libusb/libusbi.h
+++ b/libusb/libusbi.h
@@ -93,9 +93,9 @@
 /* Macro to decorate printf-like functions, in order to get
  * compiler warnings about format string mistakes.
  */
-#if __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 2)
+#ifndef _MSC_VER
 #define USBI_PRINTFLIKE(formatarg, firstvararg) \
-	__attribute__((__format__ (__printf__, formatarg, firstvararg)))
+	__attribute__ ((__format__ (__printf__, formatarg, firstvararg)))
 #else
 #define USBI_PRINTFLIKE(formatarg, firstvararg)
 #endif
@@ -254,7 +254,7 @@ void usbi_log(struct libusb_context *ctx, enum libusb_log_level level,
 void usbi_log_v(struct libusb_context *ctx, enum libusb_log_level level,
 	const char *function, const char *format, va_list args) USBI_PRINTFLIKE(4, 0);
 
-#define _usbi_log(ctx, level, ...) usbi_log(ctx, level, __FUNCTION__, __VA_ARGS__)
+#define _usbi_log(ctx, level, ...) usbi_log(ctx, level, __func__, __VA_ARGS__)
 
 #define usbi_err(ctx, ...)	_usbi_log(ctx, LIBUSB_LOG_LEVEL_ERROR, __VA_ARGS__)
 #define usbi_warn(ctx, ...)	_usbi_log(ctx, LIBUSB_LOG_LEVEL_WARNING, __VA_ARGS__)
diff --git a/libusb/os/threads_posix.c b/libusb/os/threads_posix.c
index 763cd84..71a404f 100644
--- a/libusb/os/threads_posix.c
+++ b/libusb/os/threads_posix.c
@@ -60,7 +60,7 @@ int usbi_cond_timedwait(pthread_cond_t *cond,
 
 int usbi_get_tid(void)
 {
-#ifdef HAVE_CC_THREAD_LOCAL
+#ifndef _WIN32
 	static _Thread_local int tid;
 
 	if (tid)
diff --git a/libusb/version_nano.h b/libusb/version_nano.h
index 197f76f..5708a99 100644
--- a/libusb/version_nano.h
+++ b/libusb/version_nano.h
@@ -1 +1 @@
-#define LIBUSB_NANO 11478
+#define LIBUSB_NANO 11479
diff --git a/msvc/config.h b/msvc/config.h
index b2ab24b..58d1ed7 100644
--- a/msvc/config.h
+++ b/msvc/config.h
@@ -10,6 +10,11 @@
 #error "Visual Studio 2013 or later is required."
 #endif
 
+/* Visual Studio 2013 does not support __func__ */
+#if (_MSC_VER < 1900)
+#define __func__ __FUNCTION__
+#endif
+
 /* Visual Studio 2015 and later defines timespec */
 #if (_MSC_VER >= 1900)
 #define _TIMESPEC_DEFINED 1
@@ -33,20 +38,20 @@
 #pragma warning(disable:28125)
 #endif
 
-/* Default visibility */
+/* Define to the attribute for default visibility. */
 #define DEFAULT_VISIBILITY /**/
 
-/* Uncomment to start with debug message logging enabled */
-// #define ENABLE_DEBUG_LOGGING 1
+/* Define to 1 to start with debug message logging enabled. */
+/* #undef ENABLE_DEBUG_LOGGING */
 
-/* Message logging */
+/* Define to 1 to enable message logging. */
 #define ENABLE_LOGGING 1
 
-/* Use Windows poll() implementation */
+/* Define to 1 if using the Windows poll() implementation. */
 #define POLL_WINDOWS 1
 
-/* Use Windows Threads */
+/* Define to 1 if using Windows threads. */
 #define THREADS_WINDOWS 1
 
-/* Uncomment to enabling output to system log */
-// #define USE_SYSTEM_LOGGING_FACILITY
+/* Define to 1 to output logging messages to the systemwide log. */
+/* #undef USE_SYSTEM_LOGGING_FACILITY */
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 12c5105..cb8fad9 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,5 +1,6 @@
 AM_CPPFLAGS = -I$(top_srcdir)/libusb
 LDADD = ../libusb/libusb-1.0.la
+LIBS =
 
 noinst_PROGRAMS = stress