--- orc/configure.ac.orig	2016-06-20 13:07:27.584543779 +0000
+++ orc/configure.ac	2016-06-20 13:14:21.920651349 +0000
@@ -90,20 +90,7 @@
   AS_COMPILER_FLAG(-Werror, ERROR_CFLAGS="-Werror")
 fi
 
-case "${host_os}" in
-  nobody_is_using_this_currently)
-    AC_DEFINE(HAVE_CODEMEM_MALLOC, 1, [Use malloc to allocate code for execution])
-    ;;
-  mingw*|pw32*|cygwin*)
-    AC_DEFINE(HAVE_CODEMEM_VIRTUALALLOC, 1, [Use VirtualAlloc to allocate code for execution])
-    ;;
-  linux*|darwin*|solaris*|netbsd*|freebsd*|openbsd*|kfreebsd*|dragonfly*|gnu*)
-    AC_DEFINE(HAVE_CODEMEM_MMAP, 1, [Use mmap to allocate code for execution])
-    ;;
-  *)
-    AC_ERROR([no code allocation backend])
-    ;;
-esac
+AC_CHECK_FUNCS([VirtualAlloc mmap])
 
 case "${host_os}" in
   mingw*|pw32*|cygwin*)
--- orc/orc/orccodemem.c.orig	2016-06-20 16:43:22.126619599 +0200
+++ orc/orc/orccodemem.c	2016-06-20 16:45:03.370771546 +0200
@@ -11,10 +11,10 @@
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <fcntl.h>
-#ifdef HAVE_CODEMEM_MMAP
+#ifdef HAVE_MMAP
 #include <sys/mman.h>
 #endif
-#ifdef HAVE_CODEMEM_VIRTUALALLOC
+#ifdef HAVE_VIRTUALALLOC
 #include <windows.h>
 #endif
 
@@ -190,7 +190,7 @@
   }
 }
 
-#ifdef HAVE_CODEMEM_MMAP
+#ifdef HAVE_MMAP
 int
 orc_code_region_allocate_codemem_dual_map (OrcCodeRegion *region,
     const char *dir, int force_unlink)
@@ -285,9 +285,7 @@
       "and $TMPDIR and $HOME are mounted noexec (bad).");
 }
 
-#endif
-
-#ifdef HAVE_CODEMEM_VIRTUALALLOC
+#elif defined(HAVE_VIRTUALALLOC)
 void
 orc_code_region_allocate_codemem (OrcCodeRegion *region)
 {
@@ -295,9 +293,7 @@
   region->exec_ptr = region->write_ptr;
   region->size = SIZE;
 }
-#endif
-
-#ifdef HAVE_CODEMEM_MALLOC
+#else
 void
 orc_code_region_allocate_codemem (OrcCodeRegion *region)
 {