[Libguestfs] [PATCH 1/4] ocaml: Use generational global roots.

[Richard W.M. Jones]

These are considerably more efficient than ordinary global roots, but
with the caveat that the program is not allowed to modify them without
calling a special function.  We don't modify them, so this change is
safe.

This requires OCaml >= 3.11, but we have that on RHEL 6
(since we dropped support for RHEL 5).

See also:
http://caml.inria.fr/pub/ml-archives/caml-list/2008/03/c3bf86990088236ceeb9a0f0f4c35390.en.html
---
 README            |  2 +-
 ocaml/guestfs-c.c | 16 +++++-----------
 2 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/README b/README
index 8c74901..19a1fb2 100644
--- a/README
+++ b/README
@@ -84,7 +84,7 @@ The full requirements are described below.
 +--------------+-------------+---+-----------------------------------------+
 | Pod::Simple  |             | R | Part of Perl core.                      |
 +--------------+-------------+---+-----------------------------------------+
-| OCaml        |             |R/O| Required if compiling from git.         |
+| OCaml        | 3.11        |R/O| Required if compiling from git.         |
 |              |             |   | Optional if compiling from tarball.     |
 |              |             |   | To build generated files and OCaml bindings.
 +--------------+-------------+---+-----------------------------------------+
diff --git a/ocaml/guestfs-c.c b/ocaml/guestfs-c.c
index cbff846..1ee5ba7 100644
--- a/ocaml/guestfs-c.c
+++ b/ocaml/guestfs-c.c
@@ -88,12 +88,12 @@ guestfs_finalize (value gv)
 
     /* Now unregister the global roots. */
     for (i = 0; i < len; ++i) {
-      caml_remove_global_root (roots[i]);
+      caml_remove_generational_global_root (roots[i]);
       free (roots[i]);
     }
     free (roots);
 
-    caml_remove_global_root (v);
+    caml_remove_generational_global_root (v);
     free (v);
   }
 }
@@ -179,10 +179,7 @@ ocaml_guestfs_create (value environmentv, value close_on_exitv, value unitv)
    */
   v = guestfs_int_safe_malloc (g, sizeof *v);
   *v = gv;
-  /* XXX This global root is generational, but we cannot rely on every
-   * user having the OCaml 3.11 version which supports this.
-   */
-  caml_register_global_root (v);
+  caml_register_generational_global_root (v);
   guestfs_set_private (g, "_ocaml_g", v);
 
   CAMLreturn (gv);
@@ -255,10 +252,7 @@ ocaml_guestfs_set_event_callback (value gv, value closure, value events)
     ocaml_guestfs_raise_error (g, "set_event_callback");
   }
 
-  /* XXX This global root is generational, but we cannot rely on every
-   * user having the OCaml 3.11 version which supports this.
-   */
-  caml_register_global_root (root);
+  caml_register_generational_global_root (root);
 
   snprintf (key, sizeof key, "_ocaml_event_%d", eh);
   guestfs_set_private (g, key, root);
@@ -280,7 +274,7 @@ ocaml_guestfs_delete_event_callback (value gv, value ehv)
 
   value *root = guestfs_get_private (g, key);
   if (root) {
-    caml_remove_global_root (root);
+    caml_remove_generational_global_root (root);
     free (root);
     guestfs_set_private (g, key, NULL);
     guestfs_delete_event_callback (g, eh);
-- 
2.5.0