configure: cache mmap MAP_SIZE detection

aclocal.m4

@@ -225,9 +225,9 @@ camlPervasives__loop_1128:
   ])])
 
 AC_DEFUN([OCAML_MMAP_SUPPORTS_MAP_STACK], [
-  AC_MSG_CHECKING([whether mmap supports MAP_STACK])
-  AC_RUN_IFELSE(
-    [AC_LANG_PROGRAM([[
+  AC_CACHE_CHECK([whether mmap supports MAP_STACK],
+    [ocaml_cv_func_mmap_MAP_STACK],
+    [AC_RUN_IFELSE([AC_LANG_PROGRAM([[
 #include <sys/mman.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -239,10 +239,9 @@ AC_DEFUN([OCAML_MMAP_SUPPORTS_MAP_STACK], [
   if (block == MAP_FAILED)
      return 1;
     ]])],
-    [has_mmap_map_stack=true
-    AC_MSG_RESULT([yes])],
-    [AC_MSG_RESULT([no])],
-    [AC_MSG_RESULT([no assumed])])
+      [ocaml_cv_func_mmap_MAP_STACK=yes],
+      [ocaml_cv_func_mmap_MAP_STACK=no],
+      [ocaml_cv_func_mmap_MAP_STACK='no assumed'])])
 ])
 
 AC_DEFUN([OCAML_MMAP_SUPPORTS_HUGE_PAGES], [

configure.ac

@@ -2386,21 +2386,19 @@ AS_IF([test x"$enable_flat_float_array" = "xno"],
 
 OCAML_MMAP_SUPPORTS_MAP_STACK
 AS_IF([test x"$enable_mmap_map_stack" = "xyes"],
-  [AS_IF([test x"$has_mmap_map_stack" = "xtrue"],
+  [AS_IF([test x"$ocaml_cv_func_mmap_MAP_STACK" = "xyes"],
     [AS_CASE([$target],
        [*-freebsd*],
-         [AC_MSG_ERROR([mmap MAP_STACK not supported on FreeBSD])],
-       [with_mmap_map_stack=true;
-        AC_DEFINE([USE_MMAP_MAP_STACK], [1])])],
-    [AC_MSG_ERROR([mmap MAP_STACK requested but not found on $target])])
-  ],
+         [AC_MSG_ERROR([mmap MAP_STACK is not supported on FreeBSD])],
+       [use_mmap_map_stack=true])],
+    [AC_MSG_ERROR([mmap MAP_STACK requested but not found on $target])])],
   [AS_CASE([$target],
     [*-openbsd*],
-     [with_mmap_map_stack=true;
-      AC_DEFINE([USE_MMAP_MAP_STACK], [1])
-      AC_MSG_NOTICE([using MAP_STACK on OpenBSD due to stack checking])],
-    [with_mmap_map_stack=false])
-  ])
+     [use_mmap_map_stack=true
+      AC_MSG_NOTICE([Using MAP_STACK on OpenBSD due to stack checking])])])
+
+AS_IF([$use_mmap_map_stack],
+  [AC_DEFINE([USE_MMAP_MAP_STACK], [1], [Define to use mmap MAP_STACK.])])
 
 oc_native_compflags=''