[Xen-devel] [PATCH v3 for-4.7 14/16] oxenstored: fix error when shifting negative value

[Roger Pau Monne <roger.pau@xxxxxxxxxx>]

By explicitly casting it to unsigned.

Reasoning on why this is needed, provided by Andrew Cooper:

"Ocaml stores integers shifted left by one, and with the bottom bit set.

Values with the bottom bit clear are pointers into the GC'd heap. Values
with the bottom bit set are integers, and need to be shifted by 1 bit to
have calculations performed."

Signed-off-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
Cc: Ian Jackson <ian.jackson@xxxxxxxxxxxxx>
Cc: Wei Liu <wei.liu2@xxxxxxxxxx>
---
Changes since v2:
 - Expand commit message with Andrew's reasoning.
---
 tools/ocaml/xenstored/systemd_stubs.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/ocaml/xenstored/systemd_stubs.c 
b/tools/ocaml/xenstored/systemd_stubs.c
index 1bd5dea..a78a72b 100644
--- a/tools/ocaml/xenstored/systemd_stubs.c
+++ b/tools/ocaml/xenstored/systemd_stubs.c
@@ -124,7 +124,7 @@ CAMLprim value ocaml_sd_listen_fds(value connect_to)
        CAMLparam1(connect_to);
        CAMLlocal1(sock_ret);
 
-       sock_ret = Val_int(-1);
+       sock_ret = Val_int(-1U);
 
        CAMLreturn(sock_ret);
 }
@@ -144,7 +144,7 @@ CAMLprim value ocaml_sd_notify_ready(value ignore)
        CAMLparam1(ignore);
        CAMLlocal1(ret);
 
-       ret = Val_int(-1);
+       ret = Val_int(-1U);
 
        CAMLreturn(ret);
 }
-- 
2.6.4 (Apple Git-63)


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