# threads.m4 --
#
#	This file provides a set of autoconf macros to help 
#	pilot-link find threads support
#

AC_DEFUN([PILOT_LINK_THREADS_SUPPORT], [
	use_threads=false
	AC_ARG_ENABLE(threads,[  --enable-threads        Add this to have built-in thread safety],use_threads=true)
	if $use_threads; then
		ACX_PTHREAD
		if test x"$acx_pthread_ok" = xno; then
			use_threads=false
		fi
	else
		AC_DEFINE(HAVE_PTHREADS, 0, [Define if we have pthreads])
		use_threads=false
	fi
])

# ------------------------------------------------
# ACX_PTHREAD
#  Steven G. Johnson <stevenj@alum.mit.edu>
# http://autoconf-archive.cryp.to/acx_pthread.html
# ------------------------------------------------
AC_DEFUN([ACX_PTHREAD], [
	AC_REQUIRE([AC_CANONICAL_HOST])
	AC_LANG_SAVE
	AC_LANG_C
	acx_pthread_ok=no

	# We used to check for pthread.h first, but this fails if pthread.h
	# requires special compiler flags (e.g. on True64 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"$PTHREAD_LIBS$PTHREAD_CFLAGS" != x; then
			save_CFLAGS="$CFLAGS"
			CFLAGS="$CFLAGS $PTHREAD_CFLAGS"
			save_LIBS="$LIBS"
			LIBS="$PTHREAD_LIBS $LIBS"
			AC_MSG_CHECKING([for pthread_join in LIBS=$PTHREAD_LIBS with CFLAGS=$PTHREAD_CFLAGS])
			AC_TRY_LINK_FUNC(pthread_join, acx_pthread_ok=yes)
			AC_MSG_RESULT($acx_pthread_ok)
			if test x"$acx_pthread_ok" = xno; then
					PTHREAD_LIBS=""
					PTHREAD_CFLAGS=""
			fi
			LIBS="$save_LIBS"
			CFLAGS="$save_CFLAGS"
	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 starting with a "-" are
	# C compiler flags, and other 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.

	acx_pthread_flags="pthreads none -Kthread -kthread lthread -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)
	# -kthread: FreeBSD kernel threads (preferred to -pthread since SMP-able)
	# lthread: LinuxThreads port on FreeBSD (also preferred to -pthread)
	# -pthread: Linux/gcc (kernel threads), BSD/gcc (userland threads)
	# -pthreads: Solaris/gcc
	# -mthreads: Mingw32/gcc, Lynx/gcc
	# -mt: Sun Workshop C (may only link SunOS threads [-lthread], but it
	#      doesn't hurt to check since this sometimes defines pthreads too;
	#      also defines -D_REENTRANT)
	# pthread: Linux, etcetera
	# --thread-safe: KAI C++
	# pthread-config: use pthread-config program (for GNU Pth library)

	case "${host_cpu}-${host_os}" in
			*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.  (We need to link with -pthread or
			# -lpthread.)  (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 just look for -pthreads and -lpthread first:

			acx_pthread_flags="-pthread -pthreads pthread -mt $acx_pthread_flags"
			;;
	esac

	if test x"$acx_pthread_ok" = xno; then
	for flag in $acx_pthread_flags; do

			case $flag in
					none)
					AC_MSG_CHECKING([whether pthreads work without any flags])
					;;

					-*)
					AC_MSG_CHECKING([whether pthreads work with $flag])
					PTHREAD_CFLAGS="$flag"
					;;

					pthread-config)
					AC_CHECK_PROG(acx_pthread_config, pthread-config, yes, no)
					if test x"$acx_pthread_config" = xno; then continue; fi
					PTHREAD_CFLAGS="`pthread-config --cflags`"
					PTHREAD_LIBS="`pthread-config --ldflags` `pthread-config --libs`"
					;;

					*)
					AC_MSG_CHECKING([for the pthreads library -l$flag])
					PTHREAD_LIBS="-l$flag"
					;;
			esac

			save_LIBS="$LIBS"
			save_CFLAGS="$CFLAGS"
			LIBS="$PTHREAD_LIBS $LIBS"
			CFLAGS="$CFLAGS $PTHREAD_CFLAGS"

			# 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_TRY_LINK([#include <pthread.h>],
						[pthread_t th; pthread_join(th, 0);
						 pthread_attr_init(0); pthread_cleanup_push(0, 0);
						 pthread_create(0,0,0,0); pthread_cleanup_pop(0); ],
						[acx_pthread_ok=yes])

			LIBS="$save_LIBS"
			CFLAGS="$save_CFLAGS"

			AC_MSG_RESULT($acx_pthread_ok)
			if test "x$acx_pthread_ok" = xyes; then
					break;
			fi

			PTHREAD_LIBS=""
			PTHREAD_CFLAGS=""
	done
	fi

	# Various other checks:
	if test "x$acx_pthread_ok" = xyes; then
			save_LIBS="$LIBS"
			LIBS="$PTHREAD_LIBS $LIBS"
			save_CFLAGS="$CFLAGS"
			CFLAGS="$CFLAGS $PTHREAD_CFLAGS"

			# Detect AIX lossage: JOINABLE attribute is called UNDETACHED.
			AC_MSG_CHECKING([for joinable pthread attribute])
			attr_name=unknown
			for attr in PTHREAD_CREATE_JOINABLE PTHREAD_CREATE_UNDETACHED; do
				AC_TRY_LINK([#include <pthread.h>], [int attr=$attr;],
							[attr_name=$attr; break])
			done
			AC_MSG_RESULT($attr_name)
			if test "$attr_name" != PTHREAD_CREATE_JOINABLE; then
				AC_DEFINE_UNQUOTED(PTHREAD_CREATE_JOINABLE, $attr_name,
								   [Define to necessary symbol if this constant
									uses a non-standard name on your system.])
			fi

			AC_MSG_CHECKING([if more special flags are required for pthreads])
			flag=no
			case "${host_cpu}-${host_os}" in
				*-aix* | *-freebsd* | *-darwin*) flag="-D_THREAD_SAFE";;
				*solaris* | *-osf* | *-hpux*) flag="-D_REENTRANT";;
			esac
			AC_MSG_RESULT(${flag})
			if test "x$flag" != xno; then
				PTHREAD_CFLAGS="$flag $PTHREAD_CFLAGS"
			fi

			LIBS="$save_LIBS"
			CFLAGS="$save_CFLAGS"

			# More AIX lossage: must compile with cc_r
			AC_CHECK_PROG(PTHREAD_CC, cc_r, cc_r, ${CC})
	else
			PTHREAD_CC="$CC"
	fi

	AC_SUBST(PTHREAD_LIBS)
	AC_SUBST(PTHREAD_CFLAGS)
	AC_SUBST(PTHREAD_CC)

	# Finally, execute ACTION-IF-FOUND/ACTION-IF-NOT-FOUND:
	if test x"$acx_pthread_ok" = xyes; then
			ifelse([$1],,AC_DEFINE(HAVE_PTHREAD,1,[Define if you have POSIX threads libraries and header files.]),[$1])
			:
	else
			acx_pthread_ok=no
			$2
	fi
	AC_LANG_RESTORE
])dnl ACX_PTHREAD