This is not strictly necessary since it is essentially a no-op currently: a cast to void* and value*, even in OCaml 5.0.
However it does make it clearer that what we have here is not a regular OCaml value, but one allocated with Abstract_tag or Custom_tag, and follows the example from the manual more closely: https://v2.ocaml.org/manual/intfc.html#ss:c-outside-head It also makes it clearer that these modules have been reviewed for compat with OCaml 5.0. We cannot use OCaml finalizers here, because we want control over when to unmap these pages from remote domains. A follow-up commit will add use-after-free detection instead. No functional change. Signed-off-by: Edwin Török <edvin.to...@citrix.com> Acked-by: Christian Lindig <christian.lin...@citrix.com> --- Reason for inclusion in 4.17: - make code follow best practice for upcoming OCaml 5.0 compiler (already in beta) Changes since v2: - add Acked-by line Changes since v3: - mention that use-after-free is fixed in another commit, and we cannot use finalizers here --- tools/ocaml/libs/mmap/mmap_stubs.h | 4 ++++ tools/ocaml/libs/mmap/xenmmap_stubs.c | 2 +- tools/ocaml/libs/xb/xs_ring_stubs.c | 2 +- 3 files changed, 6 insertions(+), 2 deletions(-) diff --git a/tools/ocaml/libs/mmap/mmap_stubs.h b/tools/ocaml/libs/mmap/mmap_stubs.h index 65e4239890..66f18d4406 100644 --- a/tools/ocaml/libs/mmap/mmap_stubs.h +++ b/tools/ocaml/libs/mmap/mmap_stubs.h @@ -30,4 +30,8 @@ struct mmap_interface int len; }; +#ifndef Data_abstract_val +#define Data_abstract_val(x) ((void*)(value*)(x)) +#endif + #endif diff --git a/tools/ocaml/libs/mmap/xenmmap_stubs.c b/tools/ocaml/libs/mmap/xenmmap_stubs.c index e2ce088e25..141dedb78c 100644 --- a/tools/ocaml/libs/mmap/xenmmap_stubs.c +++ b/tools/ocaml/libs/mmap/xenmmap_stubs.c @@ -28,7 +28,7 @@ #include <caml/fail.h> #include <caml/callback.h> -#define Intf_val(a) ((struct mmap_interface *) a) +#define Intf_val(a) ((struct mmap_interface *) Data_abstract_val(a)) static int mmap_interface_init(struct mmap_interface *intf, int fd, int pflag, int mflag, diff --git a/tools/ocaml/libs/xb/xs_ring_stubs.c b/tools/ocaml/libs/xb/xs_ring_stubs.c index 7a91fdee75..cc9114029f 100644 --- a/tools/ocaml/libs/xb/xs_ring_stubs.c +++ b/tools/ocaml/libs/xb/xs_ring_stubs.c @@ -35,7 +35,7 @@ #include <sys/mman.h> #include "mmap_stubs.h" -#define GET_C_STRUCT(a) ((struct mmap_interface *) a) +#define GET_C_STRUCT(a) ((struct mmap_interface *) Data_abstract_val(a)) /* * Bytes_val has been introduced by Ocaml 4.06.1. So define our own version -- 2.34.1
