r15183: Hoist the critical sizes initialiser into a header so that modules

can have standard access to critical sizes. Add a convenience function
to determine whether two critical sizes differ.
(This used to be commit 7ced96d2d348701734cc4cdf3f8899dbce8cd0f7)

2 files changed, 48 insertions, 9 deletions

diff --git a/source4/ntvfs/ntvfs.h b/source4/ntvfs/ntvfs.h
index ec1f741fa8..3d12c5efc9 100644
--- a/source4/ntvfs/ntvfs.h
+++ b/source4/ntvfs/ntvfs.h
@@ -266,6 +266,17 @@ struct ntvfs_critical_sizes {
 	int sizeof_ntvfs_request;
 };
 
+#define NTVFS_CURRENT_CRITICAL_SIZES(c) \
+    struct ntvfs_critical_sizes c = { \
+	.interface_version		= NTVFS_INTERFACE_VERSION, \
+	.sizeof_ntvfs_critical_sizes	= sizeof(struct ntvfs_critical_sizes), \
+	.sizeof_ntvfs_context		= sizeof(struct ntvfs_context), \
+	.sizeof_ntvfs_module_context	= sizeof(struct ntvfs_module_context), \
+	.sizeof_ntvfs_ops		= sizeof(struct ntvfs_ops), \
+	.sizeof_ntvfs_async_state	= sizeof(struct ntvfs_async_state), \
+	.sizeof_ntvfs_request		= sizeof(struct ntvfs_request), \
+    }
+
 struct messaging_context;
 #include "librpc/gen_ndr/security.h"
 #include "librpc/gen_ndr/notify.h"
diff --git a/source4/ntvfs/ntvfs_base.c b/source4/ntvfs/ntvfs_base.c
index b1efb44ec7..1705bbef2f 100644
--- a/source4/ntvfs/ntvfs_base.c
+++ b/source4/ntvfs/ntvfs_base.c
@@ -98,21 +98,49 @@ _PUBLIC_ const struct ntvfs_ops *ntvfs_backend_byname(const char *name, enum ntv
   This can be used by backends to either detect compilation errors, or provide
   multiple implementations for different smbd compilation options in one module
 */
-static const struct ntvfs_critical_sizes critical_sizes = {
-	.interface_version		= NTVFS_INTERFACE_VERSION,
-	.sizeof_ntvfs_critical_sizes	= sizeof(struct ntvfs_critical_sizes),
-	.sizeof_ntvfs_context		= sizeof(struct ntvfs_context),
-	.sizeof_ntvfs_module_context	= sizeof(struct ntvfs_module_context),
-	.sizeof_ntvfs_ops		= sizeof(struct ntvfs_ops),
-	.sizeof_ntvfs_async_state	= sizeof(struct ntvfs_async_state),
-	.sizeof_ntvfs_request		= sizeof(struct ntvfs_request),
-};
+
+static const NTVFS_CURRENT_CRITICAL_SIZES(critical_sizes);
 
 _PUBLIC_ const struct ntvfs_critical_sizes *ntvfs_interface_version(void)
 {
 	return &critical_sizes;
 }
 
+_PUBLIC_ BOOL ntvfs_interface_differs(const struct ntvfs_critical_sizes *const iface)
+{
+	/* The comparison would be easier with memcmp, but compiler-interset
+	 * alignment padding is not guaranteed to be zeroed.
+	 */
+
+#define FIELD_DIFFERS(field) (iface->field != critical_sizes.field)
+
+	if (FIELD_DIFFERS(interface_version))
+		return True;
+
+	if (FIELD_DIFFERS(sizeof_ntvfs_critical_sizes))
+		return True;
+
+	if (FIELD_DIFFERS(sizeof_ntvfs_context))
+		return True;
+
+	if (FIELD_DIFFERS(sizeof_ntvfs_module_context))
+		return True;
+
+	if (FIELD_DIFFERS(sizeof_ntvfs_ops))
+		return True;
+
+	if (FIELD_DIFFERS(sizeof_ntvfs_async_state))
+		return True;
+
+	if (FIELD_DIFFERS(sizeof_ntvfs_request))
+		return True;
+
+	/* Versions match. */
+	return False;
+
+#undef FIELD_DIFFERS
+}
+
 
 /*
   initialise a connection structure to point at a NTVFS backend