-# Can we rebuild the parsers?
-# We really want flex and refuse other lex. So, the parser is portable and
-# does not induce extra lib dependency
-AC_PROG_LEX
-if test "$LEX" != flex; then
- AC_MSG_NOTICE([Will not rebuild the parsers. I want flex.])
- LEX="$SHELL $missing_dir/missing flex";
+SG_CONFIGURE_PART(Checking GRAS architecture signature...)
+# Check architecture signature begin
+GRAS_ARCH
+# Check architecture signature end
+GRAS_CHECK_STRUCT_COMPACTION
+
+
+dnl ##
+dnl ## CONTEXT IMPLEMENTATION
+dnl ##
+
+SG_CONFIGURE_PART([Checking for threads, contexts or assimilated...])
+
+dnl #
+dnl # 1. determine possibilities
+dnl #
+
+dnl # check for MCSC method
+AC_MSG_CHECKING(on top of what can we build the contexts)
+AC_CHECK_HEADER(ucontext.h,,, [#include <sys/types.h>])
+AC_CHECK_FUNCS(makecontext swapcontext getcontext setcontext)
+AC_CHECK_MCSC(mcsc=yes, mcsc=no)
+
+dnl # check for pthread method
+AC_CHECK_HEADERS([pthread.h])
+AC_CHECK_LIB(pthread,pthread_create,pthread=yes, pthread=no)
+
+dnl #
+dnl # 2. make a general decision
+dnl #
+
+if test ".$mcsc" = .yes; then
+ mcsc=yes
+elif test ".$pthread" = .yes; then
+ pthread=yes