[Xen-devel] [PATCH] compat: Allow CHECK_FIELD_COMMON_ macro deal with fields that are handles

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

CHECK_FIELD_COMMON_ and CHECK_FIELD_COMMON macros verify whether the field in
64- and 32-bit versions of a structure is at the same offset by comparing
address of the field in both structures.

However, if the field itself is a handle, it is either

typedef struct {
    <type> *p;
} __guest_handle_<type>

or

typedef struct {
    compat_ptr_t c;
    <type> *_[0] __attribute__((__packed__));
} __compat_handle_<type>

and compiler will warn that we are trying to compare addresses of different
structures.

By casting the addresses to (void *) we will avoid this warning.

Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
---
 xen/include/xen/compat.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/xen/include/xen/compat.h b/xen/include/xen/compat.h
index ca60699..6de2d14 100644
--- a/xen/include/xen/compat.h
+++ b/xen/include/xen/compat.h
@@ -158,14 +158,14 @@ static inline int name(xen_ ## t ## _t *x, compat_ ## t 
## _t *c) \
 { \
     BUILD_BUG_ON(offsetof(xen_ ## t ## _t, f) != \
                  offsetof(compat_ ## t ## _t, f)); \
-    return &x->f == &c->f; \
+    return (void *)&x->f == (void *)&c->f; \
 }
 #define CHECK_FIELD_COMMON_(k, name, n, f) \
 static inline int name(k xen_ ## n *x, k compat_ ## n *c) \
 { \
     BUILD_BUG_ON(offsetof(k xen_ ## n, f) != \
                  offsetof(k compat_ ## n, f)); \
-    return &x->f == &c->f; \
+    return (void *)&x->f == (void *)&c->f; \
 }
 
 #define CHECK_FIELD(t, f) \
-- 
1.8.1.4


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