faux.net: faux_send(), iovec, pthread lib

configure.ac

@@ -156,5 +156,11 @@ AC_CHECK_HEADERS(dlfcn.h, [
           AC_MSG_ERROR([dlfcn.h not found: the dl operations is not supported])
     ])
 
+################################
+# Check for pthread
+################################
+AX_PTHREAD
+
+
 AC_CONFIG_FILES([Makefile])
 AC_OUTPUT

faux/Makefile.am

@@ -1,9 +1,10 @@
 lib_LTLIBRARIES += libfaux.la
 libfaux_la_SOURCES =
-libfaux_la_LIBADD =
+libfaux_la_LIBADD = $(PTHREAD_LIBS)
+libfaux_la_CFLAGS = $(PTHREAD_CFLAGS)
 
 if TESTC
-libfaux_la_CFLAGS = -DTESTC
+libfaux_la_CFLAGS += -DTESTC
 endif
 
 nobase_include_HEADERS += \

faux/net/net.c

@@ -2,6 +2,9 @@
  * @brief Network related functions.
  */
 
+// For ppol()
+#define _GNU_SOURCE
+
 #include <stdlib.h>
 #include <unistd.h>
 #include <assert.h>
@@ -11,18 +14,29 @@
 #include <sys/socket.h>
 #include <sys/uio.h>
 #include <signal.h>
+#include <poll.h>
 
 #include "faux/faux.h"
 #include "faux/time.h"
 #include "faux/net.h"
 
+
+/** @brief Sends data to socket. Uses timeout and signal mask.
+ *
+ * The function acts like a pselect(). It gets timeout interval to interrupt
+ * too long sending. It gets signal mask to atomically set it while blocking
+ * within select() like function. But it doesn't blocks signals before it.
+ * User code must do it. The function can be interrupted by unblocked signal or
+ * by timeout. Else it will send() all data given.
+ *
+ * @param [in] fd Socket.
+ * @param [in] buf Buffer to write.
+ * @param [in] n Number of bytes to write.
+ * @return Number of bytes written or < 0 on error.
+ */
 ssize_t faux_send(int fd, const void *buf, size_t n,
 	const struct timespec *timeout, const sigset_t *sigmask)
 {
-	sigset_t all_sigmask = {}; // All signals mask
-	sigset_t orig_sigmask = {}; // Saved signal mask
-	fd_set fdset = {};
-	ssize_t bytes_written = 0;
 	size_t total_written = 0;
 	size_t left = n;
 	const void *data = buf;
@@ -36,16 +50,6 @@ ssize_t faux_send(int fd, const void *buf, size_t n,
 	if (0 == n)
 		return 0;
 
-	// Block signals to prevent race conditions right before pselect()
-	// Catch signals while pselect() only
-	// Now blocks all signals
-	sigfillset(&all_sigmask);
-	sigprocmask(SIG_SETMASK, &all_sigmask, &orig_sigmask);
-
-	// Handlers for pselect()
-	FD_ZERO(&fdset);
-	FD_SET(fd, &fdset);
-
 	// Calculate deadline - the time when timeout must occur.
 	if (timeout) {
 		faux_timespec_now(&now);
@@ -53,7 +57,9 @@ ssize_t faux_send(int fd, const void *buf, size_t n,
 	}
 
 	do {
-		struct timespec *select_timeout = NULL;
+		ssize_t bytes_written = 0;
+		struct pollfd fds = {};
+		struct timespec *poll_timeout = NULL;
 		struct timespec to = {};
 		int sn = 0;
 
@@ -62,25 +68,38 @@ ssize_t faux_send(int fd, const void *buf, size_t n,
 				break; // Timeout already occured
 			faux_timespec_now(&now);
 			faux_timespec_diff(&to, &deadline, &now);
-			select_timeout = &to;
+			poll_timeout = &to;
 		}
 
-		sn = pselect(fd + 1, 0, &fdset, 0, select_timeout, sigmask);
+		// Handlers for poll()
+		faux_bzero(&fds, sizeof(fds));
+		fds.fd = fd;
+		fds.events = POLLOUT;
+
+		sn = ppoll(&fds, 1, poll_timeout, sigmask);
+		// When kernel can't allocate some internal structures it can
+		// return EAGAIN so retry.
+		if ((sn < 0) && (EAGAIN == errno))
+			continue;
 		// All unneded signals are masked so don't process EINTR
 		// in special way. Just break the loop
 		if (sn < 0)
 			break;
-
 		// Timeout: break the loop. User don't want to wait any more
 		if (0 == sn)
 			break;
+		// Some unknown event (not POLLOUT). So retry polling
+		if (!(fds.revents & POLLOUT))
+			continue;
 
-		bytes_written = send(fd, data, left, 0);
-		// The send() call can't be interrupted because all signals are
-		// blocked now. So any "-1" result is a really error.
+		// The send() call is non-blocking but it's not obvious that
+		// it can't return EINTR. Probably it can. Due to the fact the
+		// call is non-blocking re-send() on any signal i.e. any EINTR.
+		do {
+			bytes_written = send(fd, data, left, MSG_DONTWAIT | MSG_NOSIGNAL);
+		} while ((bytes_written < 0) && (EINTR == errno));
 		if (bytes_written < 0)
 			break;
-
 		// Insufficient space
 		if (0 == bytes_written)
 			break;
@@ -91,27 +110,16 @@ ssize_t faux_send(int fd, const void *buf, size_t n,
 
 	} while (left > 0);
 
-	sigprocmask(SIG_SETMASK, &orig_sigmask, NULL);
-
 	return total_written;
 }
 
-
-/** @brief Sends data to socket.
- *
- * The system send() can be interrupted by signal. This function will retry to
- * send in a case of interrupted call.
- *
- * @param [in] fd Socket.
- * @param [in] buf Buffer to write.
- * @param [in] n Number of bytes to write.
- * @param [in] flags Flags.
- * @return Number of bytes written or < 0 on error.
- */
-#if 0
-ssize_t faux_send(int fd, const void *buf, size_t n, int flags)
+ssize_t faux_send_block(int fd, const void *buf, size_t n,
+	const struct timespec *timeout, const sigset_t *sigmask,
+	int (*isbreak_func)(void))
 {
-	ssize_t bytes_written = 0;
+	sigset_t all_sigmask = {}; // All signals mask
+	sigset_t orig_sigmask = {}; // Saved signal mask
+	ssize_t bytes_num = 0;
 
 	assert(fd != -1);
 	assert(buf);
@@ -120,88 +128,81 @@ ssize_t faux_send(int fd, const void *buf, size_t n, int flags)
 	if (0 == n)
 		return 0;
 
-	do {
-		bytes_written = send(fd, buf, n, flags);
-	} while ((bytes_written < 0) && (EINTR == errno));
-
-	return bytes_written;
-}
+	// Block signals to prevent race conditions right before pselect()
+	// Catch signals while pselect() only
+	// Now blocks all signals
+	sigfillset(&all_sigmask);
+	pthread_sigmask(SIG_SETMASK, &all_sigmask, &orig_sigmask);
 
+	// Signal handler can set var to interrupt exchange.
+	// Get value of this var by special callback function.
+	if (isbreak_func && isbreak_func())
+		return -1;
 
-/** @brief Sends data block to socket.
- *
- * The system send() can be interrupted by signal or can write less bytes
- * than specified. This function will continue to send data until all data
- * will be sent or error occured.
- *
- * @param [in] fd Socket.
- * @param [in] buf Buffer to write.
- * @param [in] n Number of bytes to write.
- * @param [in] flags Flags.
- * @return Number of bytes written.
- * < n then insufficient space or error (but some data was already written).
- * < 0 - error.
- */
-ssize_t faux_send_block(int fd, const void *buf, size_t n, int flags)
-{
-	ssize_t bytes_written = 0;
-	size_t total_written = 0;
-	size_t left = n;
-	const void *data = buf;
+	bytes_num = faux_send(fd, buf, n, timeout, sigmask);
 
-	do {
-		bytes_written = faux_send(fd, data, left, flags);
-		if (bytes_written < 0) { // Error
-			if (total_written != 0)
-				return total_written;
-			return -1;
-		}
-		if (0 == bytes_written) // Insufficient space
-			return total_written;
-		data += bytes_written;
-		left = left - bytes_written;
-		total_written += bytes_written;
-	} while (left > 0);
+	pthread_sigmask(SIG_SETMASK, &orig_sigmask, NULL);
 
-	return total_written;
+	return bytes_num;
 }
 
 
 /** @brief Sends struct iovec data blocks to socket.
  *
- * This function is like a faux_send_block() function but uses scatter/gather.
+ * This function is like a faux_send() function but uses scatter/gather.
  *
- * @see faux_send_block().
+ * @see faux_send().
  * @param [in] fd Socket.
  * @param [in] buf Buffer to write.
  * @param [in] n Number of bytes to write.
  * @param [in] flags Flags.
  * @return Number of bytes written.
- * < n then insufficient space or error (but some data was already written).
+ * < total_length then insufficient space, timeout or
+ * error (but some data were already sent).
  * < 0 - error.
  */
-ssize_t faux_sendv_block(int fd, const struct iovec *iov, int iovcnt, int flags)
+ssize_t faux_sendv(int fd, const struct iovec *iov, int iovcnt,
+	const struct timespec *timeout, const sigset_t *sigmask)
 {
-	ssize_t bytes_written = 0;
 	size_t total_written = 0;
 	int i = 0;
+	struct timespec now = {};
+	struct timespec deadline = {};
 
 	if (!iov)
 		return -1;
 	if (iovcnt == 0)
 		return 0;
 
+	// Calculate deadline - the time when timeout must occur.
+	if (timeout) {
+		faux_timespec_now(&now);
+		faux_timespec_sum(&deadline, &now, timeout);
+	}
+
 	for (i = 0; i < iovcnt; i++) {
+		ssize_t bytes_written = 0;
+		struct timespec *send_timeout = NULL;
+		struct timespec to = {};
+
+		if (timeout) {
+			if (faux_timespec_before_now(&deadline))
+				break; // Timeout already occured
+			faux_timespec_now(&now);
+			faux_timespec_diff(&to, &deadline, &now);
+			send_timeout = &to;
+		}
 		if (iov[i].iov_len == 0)
 			continue;
-		bytes_written = faux_send_block(fd, iov[i].iov_base, iov[i].iov_len, flags);
+		bytes_written = faux_send(fd, iov[i].iov_base, iov[i].iov_len,
+			send_timeout, sigmask);
 		if (bytes_written < 0) { // Error
 			if (total_written != 0)
-				return total_written;
+				break;
 			return -1;
 		}
-		if (0 == bytes_written) // Insufficient space
-			return total_written;
+		if (0 == bytes_written) // Insufficient space or timeout
+			break;
 		total_written += bytes_written;
 	}
 
@@ -209,73 +210,165 @@ ssize_t faux_sendv_block(int fd, const struct iovec *iov, int iovcnt, int flags)
 }
 
 
-/** @brief Receive data from socket.
- *
- * The system recv() can be interrupted by signal. This function will retry to
- * receive if it was interrupted by signal.
- *
- * @param [in] fd Socket.
- * @param [in] buf Buffer to write.
- * @param [in] n Number of bytes to write.
- * @param [in] flags Flags.
- * @return Number of bytes readed or < 0 on error.
- * 0 bytes indicates EOF
- */
-ssize_t faux_recv(int fd, void *buf, size_t n, int flags)
+ssize_t faux_sendv_block(int fd, const struct iovec *iov, int iovcnt,
+	const struct timespec *timeout, const sigset_t *sigmask,
+	int (*isbreak_func)(void))
 {
-	ssize_t bytes_readed = 0;
+	sigset_t all_sigmask = {}; // All signals mask
+	sigset_t orig_sigmask = {}; // Saved signal mask
+	ssize_t bytes_num = 0;
 
 	assert(fd != -1);
-	assert(buf);
-	if ((-1 == fd) || !buf)
+	if ((-1 == fd))
 		return -1;
-	if (0 == n)
+	if (!iov)
+		return -1;
+	if (iovcnt == 0)
 		return 0;
 
-	do {
-		bytes_readed = recv(fd, buf, n, flags);
-	} while ((bytes_readed < 0) && (EINTR == errno));
+	// Block signals to prevent race conditions right before pselect()
+	// Catch signals while pselect() only
+	// Now blocks all signals
+	sigfillset(&all_sigmask);
+	pthread_sigmask(SIG_SETMASK, &all_sigmask, &orig_sigmask);
+
+	// Signal handler can set var to interrupt exchange.
+	// Get value of this var by special callback function.
+	if (isbreak_func && isbreak_func())
+		return -1;
 
-	return bytes_readed;
+	bytes_num = faux_sendv(fd, iov, iovcnt, timeout, sigmask);
+
+	pthread_sigmask(SIG_SETMASK, &orig_sigmask, NULL);
+
+	return bytes_num;
 }
 
 
-/** @brief Receive data block from socket.
- *
- * The system recv() can be interrupted by signal or can read less bytes
- * than specified. This function will continue to read data until all data
- * will be readed or error occured.
- *
- * @param [in] fd Socket.
- * @param [in] buf Buffer to write.
- * @param [in] n Number of bytes to write.
- * @param [in] flags Flags.
- * @return Number of bytes readed.
- * < n EOF or error (but some data was already readed).
- * < 0 Error.
- */
-size_t faux_recv_block(int fd, void *buf, size_t n, int flags)
+ssize_t faux_recv(int fd, void *buf, size_t n,
+	const struct timespec *timeout, const sigset_t *sigmask)
 {
-	ssize_t bytes_readed = 0;
 	size_t total_readed = 0;
 	size_t left = n;
 	void *data = buf;
+	struct timespec now = {};
+	struct timespec deadline = {};
+
+	assert(fd != -1);
+	assert(buf);
+	if ((-1 == fd) || !buf)
+		return -1;
+	if (0 == n)
+		return 0;
+
+	// Calculate deadline - the time when timeout must occur.
+	if (timeout) {
+		faux_timespec_now(&now);
+		faux_timespec_sum(&deadline, &now, timeout);
+	}
 
 	do {
-		bytes_readed = recv(fd, data, left, flags);
-		if (bytes_readed < 0) {
-			if (total_readed != 0)
-				return total_readed;
-			return -1;
+		ssize_t bytes_readed = 0;
+		struct pollfd fds = {};
+		struct timespec *poll_timeout = NULL;
+		struct timespec to = {};
+		int sn = 0;
+
+		if (timeout) {
+			if (faux_timespec_before_now(&deadline))
+				break; // Timeout already occured
+			faux_timespec_now(&now);
+			faux_timespec_diff(&to, &deadline, &now);
+			poll_timeout = &to;
 		}
-		if (0 == bytes_readed) // EOF
-			return total_readed;
+
+		// Handlers for poll()
+		faux_bzero(&fds, sizeof(fds));
+		fds.fd = fd;
+		fds.events = POLLIN;
+
+		sn = ppoll(&fds, 1, poll_timeout, sigmask);
+		// When kernel can't allocate some internal structures it can
+		// return EAGAIN so retry.
+		if ((sn < 0) && (EAGAIN == errno))
+			continue;
+		// All unneded signals are masked so don't process EINTR
+		// in special way. Just break the loop
+		if (sn < 0)
+			break;
+		// Timeout: break the loop. User don't want to wait any more
+		if (0 == sn)
+			break;
+		// Some unknown event (not POLLIN). So retry polling
+		if (!(fds.revents & POLLIN))
+			continue;
+
+		// The send() call is non-blocking but it's not obvious that
+		// it can't return EINTR. Probably it can. Due to the fact the
+		// call is non-blocking re-send() on any signal i.e. any EINTR.
+		do {
+			bytes_readed = recv(fd, data, left, MSG_DONTWAIT | MSG_NOSIGNAL);
+		} while ((bytes_readed < 0) && (EINTR == errno));
+		if (bytes_readed < 0)
+			break;
+		// EOF
+		if (0 == bytes_readed)
+			break;
+
 		data += bytes_readed;
 		left = left - bytes_readed;
 		total_readed += bytes_readed;
+
 	} while (left > 0);
 
 	return total_readed;
 }
 
-#endif
+
+ssize_t faux_recvv(int fd, struct iovec *iov, int iovcnt,
+	const struct timespec *timeout, const sigset_t *sigmask)
+{
+	size_t total_readed = 0;
+	int i = 0;
+	struct timespec now = {};
+	struct timespec deadline = {};
+
+	if (!iov)
+		return -1;
+	if (iovcnt == 0)
+		return 0;
+
+	// Calculate deadline - the time when timeout must occur.
+	if (timeout) {
+		faux_timespec_now(&now);
+		faux_timespec_sum(&deadline, &now, timeout);
+	}
+
+	for (i = 0; i < iovcnt; i++) {
+		ssize_t bytes_readed = 0;
+		struct timespec *recv_timeout = NULL;
+		struct timespec to = {};
+
+		if (timeout) {
+			if (faux_timespec_before_now(&deadline))
+				break; // Timeout already occured
+			faux_timespec_now(&now);
+			faux_timespec_diff(&to, &deadline, &now);
+			recv_timeout = &to;
+		}
+		if (iov[i].iov_len == 0)
+			continue;
+		bytes_readed = faux_recv(fd, iov[i].iov_base, iov[i].iov_len,
+			recv_timeout, sigmask);
+		if (bytes_readed < 0) { // Error
+			if (total_readed != 0)
+				break;
+			return -1;
+		}
+		if (0 == bytes_readed) // EOF or timeout
+			break;
+		total_readed += bytes_readed;
+	}
+
+	return total_readed;
+}

m4/m4_ax_pthread.m4

@@ -0,0 +1,507 @@
+# ===========================================================================
+#        https://www.gnu.org/software/autoconf-archive/ax_pthread.html
+# ===========================================================================
+#
+# SYNOPSIS
+#
+#   AX_PTHREAD([ACTION-IF-FOUND[, ACTION-IF-NOT-FOUND]])
+#
+# DESCRIPTION
+#
+#   This macro figures out how to build C programs using POSIX threads. It
+#   sets the PTHREAD_LIBS output variable to the threads library and linker
+#   flags, and the PTHREAD_CFLAGS output variable to any special C compiler
+#   flags that are needed. (The user can also force certain compiler
+#   flags/libs to be tested by setting these environment variables.)
+#
+#   Also sets PTHREAD_CC to any special C compiler that is needed for
+#   multi-threaded programs (defaults to the value of CC otherwise). (This
+#   is necessary on AIX to use the special cc_r compiler alias.)
+#
+#   NOTE: You are assumed to not only compile your program with these flags,
+#   but also to link with them as well. For example, you might link with
+#   $PTHREAD_CC $CFLAGS $PTHREAD_CFLAGS $LDFLAGS ... $PTHREAD_LIBS $LIBS
+#
+#   If you are only building threaded programs, you may wish to use these
+#   variables in your default LIBS, CFLAGS, and CC:
+#
+#     LIBS="$PTHREAD_LIBS $LIBS"
+#     CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+#     CC="$PTHREAD_CC"
+#
+#   In addition, if the PTHREAD_CREATE_JOINABLE thread-attribute constant
+#   has a nonstandard name, this macro defines PTHREAD_CREATE_JOINABLE to
+#   that name (e.g. PTHREAD_CREATE_UNDETACHED on AIX).
+#
+#   Also HAVE_PTHREAD_PRIO_INHERIT is defined if pthread is found and the
+#   PTHREAD_PRIO_INHERIT symbol is defined when compiling with
+#   PTHREAD_CFLAGS.
+#
+#   ACTION-IF-FOUND is a list of shell commands to run if a threads library
+#   is found, and ACTION-IF-NOT-FOUND is a list of commands to run it if it
+#   is not found. If ACTION-IF-FOUND is not specified, the default action
+#   will define HAVE_PTHREAD.
+#
+#   Please let the authors know if this macro fails on any platform, or if
+#   you have any other suggestions or comments. This macro was based on work
+#   by SGJ on autoconf scripts for FFTW (http://www.fftw.org/) (with help
+#   from M. Frigo), as well as ac_pthread and hb_pthread macros posted by
+#   Alejandro Forero Cuervo to the autoconf macro repository. We are also
+#   grateful for the helpful feedback of numerous users.
+#
+#   Updated for Autoconf 2.68 by Daniel Richard G.
+#
+# LICENSE
+#
+#   Copyright (c) 2008 Steven G. Johnson <stevenj@alum.mit.edu>
+#   Copyright (c) 2011 Daniel Richard G. <skunk@iSKUNK.ORG>
+#   Copyright (c) 2019 Marc Stevens <marc.stevens@cwi.nl>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <https://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 27
+
+AU_ALIAS([ACX_PTHREAD], [AX_PTHREAD])
+AC_DEFUN([AX_PTHREAD], [
+AC_REQUIRE([AC_CANONICAL_HOST])
+AC_REQUIRE([AC_PROG_CC])
+AC_REQUIRE([AC_PROG_SED])
+AC_LANG_PUSH([C])
+ax_pthread_ok=no
+
+# We used to check for pthread.h first, but this fails if pthread.h
+# requires special compiler flags (e.g. on Tru64 or Sequent).
+# It gets checked for in the link test anyway.
+
+# First of all, check if the user has set any of the PTHREAD_LIBS,
+# etcetera environment variables, and if threads linking works using
+# them:
+if test "x$PTHREAD_CFLAGS$PTHREAD_LIBS" != "x"; then
+        ax_pthread_save_CC="$CC"
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        AS_IF([test "x$PTHREAD_CC" != "x"], [CC="$PTHREAD_CC"])
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+        AC_MSG_CHECKING([for pthread_join using $CC $PTHREAD_CFLAGS $PTHREAD_LIBS])
+        AC_LINK_IFELSE([AC_LANG_CALL([], [pthread_join])], [ax_pthread_ok=yes])
+        AC_MSG_RESULT([$ax_pthread_ok])
+        if test "x$ax_pthread_ok" = "xno"; then
+                PTHREAD_LIBS=""
+                PTHREAD_CFLAGS=""
+        fi
+        CC="$ax_pthread_save_CC"
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+fi
+
+# We must check for the threads library under a number of different
+# names; the ordering is very important because some systems
+# (e.g. DEC) have both -lpthread and -lpthreads, where one of the
+# libraries is broken (non-POSIX).
+
+# Create a list of thread flags to try. Items with a "," contain both
+# C compiler flags (before ",") and linker flags (after ","). Other items
+# starting with a "-" are C compiler flags, and remaining items are
+# library names, except for "none" which indicates that we try without
+# any flags at all, and "pthread-config" which is a program returning
+# the flags for the Pth emulation library.
+
+ax_pthread_flags="pthreads none -Kthread -pthread -pthreads -mthreads pthread --thread-safe -mt pthread-config"
+
+# The ordering *is* (sometimes) important.  Some notes on the
+# individual items follow:
+
+# pthreads: AIX (must check this before -lpthread)
+# none: in case threads are in libc; should be tried before -Kthread and
+#       other compiler flags to prevent continual compiler warnings
+# -Kthread: Sequent (threads in libc, but -Kthread needed for pthread.h)
+# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads), Tru64
+#           (Note: HP C rejects this with "bad form for `-t' option")
+# -pthreads: Solaris/gcc (Note: HP C also rejects)
+# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
+#      doesn't hurt to check since this sometimes defines pthreads and
+#      -D_REENTRANT too), HP C (must be checked before -lpthread, which
+#      is present but should not be used directly; and before -mthreads,
+#      because the compiler interprets this as "-mt" + "-hreads")
+# -mthreads: Mingw32/gcc, Lynx/gcc
+# pthread: Linux, etcetera
+# --thread-safe: KAI C++
+# pthread-config: use pthread-config program (for GNU Pth library)
+
+case $host_os in
+
+        freebsd*)
+
+        # -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
+        # lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
+
+        ax_pthread_flags="-kthread lthread $ax_pthread_flags"
+        ;;
+
+        hpux*)
+
+        # From the cc(1) man page: "[-mt] Sets various -D flags to enable
+        # multi-threading and also sets -lpthread."
+
+        ax_pthread_flags="-mt -pthread pthread $ax_pthread_flags"
+        ;;
+
+        openedition*)
+
+        # IBM z/OS requires a feature-test macro to be defined in order to
+        # enable POSIX threads at all, so give the user a hint if this is
+        # not set. (We don't define these ourselves, as they can affect
+        # other portions of the system API in unpredictable ways.)
+
+        AC_EGREP_CPP([AX_PTHREAD_ZOS_MISSING],
+            [
+#            if !defined(_OPEN_THREADS) && !defined(_UNIX03_THREADS)
+             AX_PTHREAD_ZOS_MISSING
+#            endif
+            ],
+            [AC_MSG_WARN([IBM z/OS requires -D_OPEN_THREADS or -D_UNIX03_THREADS to enable pthreads support.])])
+        ;;
+
+        solaris*)
+
+        # On Solaris (at least, for some versions), libc contains stubbed
+        # (non-functional) versions of the pthreads routines, so link-based
+        # tests will erroneously succeed. (N.B.: The stubs are missing
+        # pthread_cleanup_push, or rather a function called by this macro,
+        # so we could check for that, but who knows whether they'll stub
+        # that too in a future libc.)  So we'll check first for the
+        # standard Solaris way of linking pthreads (-mt -lpthread).
+
+        ax_pthread_flags="-mt,-lpthread pthread $ax_pthread_flags"
+        ;;
+esac
+
+# Are we compiling with Clang?
+
+AC_CACHE_CHECK([whether $CC is Clang],
+    [ax_cv_PTHREAD_CLANG],
+    [ax_cv_PTHREAD_CLANG=no
+     # Note that Autoconf sets GCC=yes for Clang as well as GCC
+     if test "x$GCC" = "xyes"; then
+        AC_EGREP_CPP([AX_PTHREAD_CC_IS_CLANG],
+            [/* Note: Clang 2.7 lacks __clang_[a-z]+__ */
+#            if defined(__clang__) && defined(__llvm__)
+             AX_PTHREAD_CC_IS_CLANG
+#            endif
+            ],
+            [ax_cv_PTHREAD_CLANG=yes])
+     fi
+    ])
+ax_pthread_clang="$ax_cv_PTHREAD_CLANG"
+
+
+# GCC generally uses -pthread, or -pthreads on some platforms (e.g. SPARC)
+
+# Note that for GCC and Clang -pthread generally implies -lpthread,
+# except when -nostdlib is passed.
+# This is problematic using libtool to build C++ shared libraries with pthread:
+# [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=25460
+# [2] https://bugzilla.redhat.com/show_bug.cgi?id=661333
+# [3] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=468555
+# To solve this, first try -pthread together with -lpthread for GCC
+
+AS_IF([test "x$GCC" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread -pthreads $ax_pthread_flags"])
+
+# Clang takes -pthread (never supported any other flag), but we'll try with -lpthread first
+
+AS_IF([test "x$ax_pthread_clang" = "xyes"],
+      [ax_pthread_flags="-pthread,-lpthread -pthread"])
+
+
+# The presence of a feature test macro requesting re-entrant function
+# definitions is, on some systems, a strong hint that pthreads support is
+# correctly enabled
+
+case $host_os in
+        darwin* | hpux* | linux* | osf* | solaris*)
+        ax_pthread_check_macro="_REENTRANT"
+        ;;
+
+        aix*)
+        ax_pthread_check_macro="_THREAD_SAFE"
+        ;;
+
+        *)
+        ax_pthread_check_macro="--"
+        ;;
+esac
+AS_IF([test "x$ax_pthread_check_macro" = "x--"],
+      [ax_pthread_check_cond=0],
+      [ax_pthread_check_cond="!defined($ax_pthread_check_macro)"])
+
+
+if test "x$ax_pthread_ok" = "xno"; then
+for ax_pthread_try_flag in $ax_pthread_flags; do
+
+        case $ax_pthread_try_flag in
+                none)
+                AC_MSG_CHECKING([whether pthreads work without any flags])
+                ;;
+
+                *,*)
+                PTHREAD_CFLAGS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\1/"`
+                PTHREAD_LIBS=`echo $ax_pthread_try_flag | sed "s/^\(.*\),\(.*\)$/\2/"`
+                AC_MSG_CHECKING([whether pthreads work with "$PTHREAD_CFLAGS" and "$PTHREAD_LIBS"])
+                ;;
+
+                -*)
+                AC_MSG_CHECKING([whether pthreads work with $ax_pthread_try_flag])
+                PTHREAD_CFLAGS="$ax_pthread_try_flag"
+                ;;
+
+                pthread-config)
+                AC_CHECK_PROG([ax_pthread_config], [pthread-config], [yes], [no])
+                AS_IF([test "x$ax_pthread_config" = "xno"], [continue])
+                PTHREAD_CFLAGS="`pthread-config --cflags`"
+                PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
+                ;;
+
+                *)
+                AC_MSG_CHECKING([for the pthreads library -l$ax_pthread_try_flag])
+                PTHREAD_LIBS="-l$ax_pthread_try_flag"
+                ;;
+        esac
+
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Check for various functions.  We must include pthread.h,
+        # since some functions may be macros.  (On the Sequent, we
+        # need a special flag -Kthread to make this header compile.)
+        # We check for pthread_join because it is in -lpthread on IRIX
+        # while pthread_create is in libc.  We check for pthread_attr_init
+        # due to DEC craziness with -lpthreads.  We check for
+        # pthread_cleanup_push because it is one of the few pthread
+        # functions on Solaris that doesn't have a non-functional libc stub.
+        # We try pthread_create on general principles.
+
+        AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>
+#                       if $ax_pthread_check_cond
+#                        error "$ax_pthread_check_macro must be defined"
+#                       endif
+                        static void *some_global = NULL;
+                        static void routine(void *a)
+                          {
+                             /* To avoid any unused-parameter or
+                                unused-but-set-parameter warning.  */
+                             some_global = a;
+                          }
+                        static void *start_routine(void *a) { return a; }],
+                       [pthread_t th; pthread_attr_t attr;
+                        pthread_create(&th, 0, start_routine, 0);
+                        pthread_join(th, 0);
+                        pthread_attr_init(&attr);
+                        pthread_cleanup_push(routine, 0);
+                        pthread_cleanup_pop(0) /* ; */])],
+            [ax_pthread_ok=yes],
+            [])
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        AC_MSG_RESULT([$ax_pthread_ok])
+        AS_IF([test "x$ax_pthread_ok" = "xyes"], [break])
+
+        PTHREAD_LIBS=""
+        PTHREAD_CFLAGS=""
+done
+fi
+
+
+# Clang needs special handling, because older versions handle the -pthread
+# option in a rather... idiosyncratic way
+
+if test "x$ax_pthread_clang" = "xyes"; then
+
+        # Clang takes -pthread; it has never supported any other flag
+
+        # (Note 1: This will need to be revisited if a system that Clang
+        # supports has POSIX threads in a separate library.  This tends not
+        # to be the way of modern systems, but it's conceivable.)
+
+        # (Note 2: On some systems, notably Darwin, -pthread is not needed
+        # to get POSIX threads support; the API is always present and
+        # active.  We could reasonably leave PTHREAD_CFLAGS empty.  But
+        # -pthread does define _REENTRANT, and while the Darwin headers
+        # ignore this macro, third-party headers might not.)
+
+        # However, older versions of Clang make a point of warning the user
+        # that, in an invocation where only linking and no compilation is
+        # taking place, the -pthread option has no effect ("argument unused
+        # during compilation").  They expect -pthread to be passed in only
+        # when source code is being compiled.
+        #
+        # Problem is, this is at odds with the way Automake and most other
+        # C build frameworks function, which is that the same flags used in
+        # compilation (CFLAGS) are also used in linking.  Many systems
+        # supported by AX_PTHREAD require exactly this for POSIX threads
+        # support, and in fact it is often not straightforward to specify a
+        # flag that is used only in the compilation phase and not in
+        # linking.  Such a scenario is extremely rare in practice.
+        #
+        # Even though use of the -pthread flag in linking would only print
+        # a warning, this can be a nuisance for well-run software projects
+        # that build with -Werror.  So if the active version of Clang has
+        # this misfeature, we search for an option to squash it.
+
+        AC_CACHE_CHECK([whether Clang needs flag to prevent "argument unused" warning when linking with -pthread],
+            [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG],
+            [ax_cv_PTHREAD_CLANG_NO_WARN_FLAG=unknown
+             # Create an alternate version of $ac_link that compiles and
+             # links in two steps (.c -> .o, .o -> exe) instead of one
+             # (.c -> exe), because the warning occurs only in the second
+             # step
+             ax_pthread_save_ac_link="$ac_link"
+             ax_pthread_sed='s/conftest\.\$ac_ext/conftest.$ac_objext/g'
+             ax_pthread_link_step=`$as_echo "$ac_link" | sed "$ax_pthread_sed"`
+             ax_pthread_2step_ac_link="($ac_compile) && (echo ==== >&5) && ($ax_pthread_link_step)"
+             ax_pthread_save_CFLAGS="$CFLAGS"
+             for ax_pthread_try in '' -Qunused-arguments -Wno-unused-command-line-argument unknown; do
+                AS_IF([test "x$ax_pthread_try" = "xunknown"], [break])
+                CFLAGS="-Werror -Wunknown-warning-option $ax_pthread_try -pthread $ax_pthread_save_CFLAGS"
+                ac_link="$ax_pthread_save_ac_link"
+                AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
+                    [ac_link="$ax_pthread_2step_ac_link"
+                     AC_LINK_IFELSE([AC_LANG_SOURCE([[int main(void){return 0;}]])],
+                         [break])
+                    ])
+             done
+             ac_link="$ax_pthread_save_ac_link"
+             CFLAGS="$ax_pthread_save_CFLAGS"
+             AS_IF([test "x$ax_pthread_try" = "x"], [ax_pthread_try=no])
+             ax_cv_PTHREAD_CLANG_NO_WARN_FLAG="$ax_pthread_try"
+            ])
+
+        case "$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG" in
+                no | unknown) ;;
+                *) PTHREAD_CFLAGS="$ax_cv_PTHREAD_CLANG_NO_WARN_FLAG $PTHREAD_CFLAGS" ;;
+        esac
+
+fi # $ax_pthread_clang = yes
+
+
+
+# Various other checks:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ax_pthread_save_CFLAGS="$CFLAGS"
+        ax_pthread_save_LIBS="$LIBS"
+        CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
+        LIBS="$PTHREAD_LIBS $LIBS"
+
+        # Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
+        AC_CACHE_CHECK([for joinable pthread attribute],
+            [ax_cv_PTHREAD_JOINABLE_ATTR],
+            [ax_cv_PTHREAD_JOINABLE_ATTR=unknown
+             for ax_pthread_attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
+                 AC_LINK_IFELSE([AC_LANG_PROGRAM([#include <pthread.h>],
+                                                 [int attr = $ax_pthread_attr; return attr /* ; */])],
+                                [ax_cv_PTHREAD_JOINABLE_ATTR=$ax_pthread_attr; break],
+                                [])
+             done
+            ])
+        AS_IF([test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xunknown" && \
+               test "x$ax_cv_PTHREAD_JOINABLE_ATTR" != "xPTHREAD_CREATE_JOINABLE" && \
+               test "x$ax_pthread_joinable_attr_defined" != "xyes"],
+              [AC_DEFINE_UNQUOTED([PTHREAD_CREATE_JOINABLE],
+                                  [$ax_cv_PTHREAD_JOINABLE_ATTR],
+                                  [Define to necessary symbol if this constant
+                                   uses a non-standard name on your system.])
+               ax_pthread_joinable_attr_defined=yes
+              ])
+
+        AC_CACHE_CHECK([whether more special flags are required for pthreads],
+            [ax_cv_PTHREAD_SPECIAL_FLAGS],
+            [ax_cv_PTHREAD_SPECIAL_FLAGS=no
+             case $host_os in
+             solaris*)
+             ax_cv_PTHREAD_SPECIAL_FLAGS="-D_POSIX_PTHREAD_SEMANTICS"
+             ;;
+             esac
+            ])
+        AS_IF([test "x$ax_cv_PTHREAD_SPECIAL_FLAGS" != "xno" && \
+               test "x$ax_pthread_special_flags_added" != "xyes"],
+              [PTHREAD_CFLAGS="$ax_cv_PTHREAD_SPECIAL_FLAGS $PTHREAD_CFLAGS"
+               ax_pthread_special_flags_added=yes])
+
+        AC_CACHE_CHECK([for PTHREAD_PRIO_INHERIT],
+            [ax_cv_PTHREAD_PRIO_INHERIT],
+            [AC_LINK_IFELSE([AC_LANG_PROGRAM([[#include <pthread.h>]],
+                                             [[int i = PTHREAD_PRIO_INHERIT;
+                                               return i;]])],
+                            [ax_cv_PTHREAD_PRIO_INHERIT=yes],
+                            [ax_cv_PTHREAD_PRIO_INHERIT=no])
+            ])
+        AS_IF([test "x$ax_cv_PTHREAD_PRIO_INHERIT" = "xyes" && \
+               test "x$ax_pthread_prio_inherit_defined" != "xyes"],
+              [AC_DEFINE([HAVE_PTHREAD_PRIO_INHERIT], [1], [Have PTHREAD_PRIO_INHERIT.])
+               ax_pthread_prio_inherit_defined=yes
+              ])
+
+        CFLAGS="$ax_pthread_save_CFLAGS"
+        LIBS="$ax_pthread_save_LIBS"
+
+        # More AIX lossage: compile with *_r variant
+        if test "x$GCC" != "xyes"; then
+            case $host_os in
+                aix*)
+                AS_CASE(["x/$CC"],
+                    [x*/c89|x*/c89_128|x*/c99|x*/c99_128|x*/cc|x*/cc128|x*/xlc|x*/xlc_v6|x*/xlc128|x*/xlc128_v6],
+                    [#handle absolute path differently from PATH based program lookup
+                     AS_CASE(["x$CC"],
+                         [x/*],
+                         [AS_IF([AS_EXECUTABLE_P([${CC}_r])],[PTHREAD_CC="${CC}_r"])],
+                         [AC_CHECK_PROGS([PTHREAD_CC],[${CC}_r],[$CC])])])
+                ;;
+            esac
+        fi
+fi
+
+test -n "$PTHREAD_CC" || PTHREAD_CC="$CC"
+
+AC_SUBST([PTHREAD_LIBS])
+AC_SUBST([PTHREAD_CFLAGS])
+AC_SUBST([PTHREAD_CC])
+
+# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
+if test "x$ax_pthread_ok" = "xyes"; then
+        ifelse([$1],,[AC_DEFINE([HAVE_PTHREAD],[1],[Define if you have POSIX threads libraries and header files.])],[$1])
+        :
+else
+        ax_pthread_ok=no
+        $2
+fi
+AC_LANG_POP
+])dnl AX_PTHREAD