+SG_CONFIGURE_PART(Checking GRAS architecture signature...)
+# Check architecture signature begin
+GRAS_ARCH
+# Check architecture signature end
+GRAS_CHECK_STRUCT_COMPACTION
+
+
+dnl ##
+dnl ## CONTEXT IMPLEMENTATION
+dnl ##
+
+SG_CONFIGURE_PART([Checking for threads, contexts or assimilated...])
+
+dnl #
+dnl # 1. determine possibilities
+dnl #
+
+dnl # check for MCSC method
+AC_MSG_CHECKING(on top of what can we build the contexts)
+AC_CHECK_HEADER(ucontext.h,,, [#include <sys/types.h>])
+AC_CHECK_FUNCS(makecontext swapcontext getcontext setcontext)
+AC_CHECK_MCSC(mcsc=yes, mcsc=no)
+
+dnl # check for pthread method
+AC_CHECK_HEADERS([pthread.h])
+AC_CHECK_LIB(pthread,pthread_create,pthread=yes, pthread=no)
+
+dnl #
+dnl # 2. make a general decision
+dnl #
+
+if test ".$mcsc" = .yes; then
+ mcsc=yes
+elif test ".$pthread" = .yes; then
+ pthread=yes
+else
+ ac_header=windows.h
+ as_ac_Header=`echo "ac_cv_header_$ac_header" | $as_tr_sh`
+ if test `eval echo '${'$as_ac_Header'}'` = yes; then
+ windows_context=yes
+ else
+ AC_ERROR([no appropriate backend found])
+ fi
+fi
+
+dnl #
+dnl # 3. allow decision to be overridden by user
+dnl #
+
+AC_MSG_CHECKING(what kind of backend should we use)
+AC_ARG_WITH(context,
+ [ --with-context=[ucontext/pthread] Use either (System V) swapcontext or pthread [[default=auto]].],,
+ with_context=auto)
+case $with_context in
+ ucontext) ;;
+ pthread) ;;
+ windows) ;;
+ auto) with_context=ucontext;;
+ *) AC_MSG_ERROR("--with-context must be either ucontext or pthread") ;;
+esac
+
+if test "x$with_context" = "xucontext" ; then
+ if test ".$mcsc" = .yes; then
+ AC_MSG_RESULT(found working ucontext. Great!)
+ AC_DEFINE([USE_UCONTEXT],1,[Define if we use ucontext or not])
+ else
+ if test ".$windows_context" = .yes ; then
+ AC_MSG_RESULT(use windows context portability layer.)
+ with_context=windows
+ else
+ AC_MSG_RESULT([[no working ucontext found. Try pthreads as a fallback]])
+ with_context=pthread
+ fi
+ fi
+fi
+
+if test "x$with_context" = "xpthread"; then
+ AC_CHECK_HEADERS([pthread.h])
+ AC_CHECK_LIB(pthread,pthread_create,,
+ [AC_MSG_ERROR([[Cannot find pthreads, no way (try --with-context=ucontext if you haven't already tried).]])])
+ AC_DEFINE([USE_PTHREADS],1,[Define if we use pthreads or not])
+ AC_MSG_RESULT(You have pthreads. Let's use them.)