[ovs-dev] [PATCH] util: Avoid uninitialized pointer complaints from Coverity.
Ben Pfaff
blp at nicira.com
Thu Feb 24 23:34:51 UTC 2011
---
lib/util.h | 18 +++++++++++++++++-
1 files changed, 17 insertions(+), 1 deletions(-)
diff --git a/lib/util.h b/lib/util.h
index 635d331..e533987 100644
--- a/lib/util.h
+++ b/lib/util.h
@@ -85,6 +85,22 @@ extern const char *program_name;
#define OVS_TYPEOF(OBJECT) void *
#endif
+/* Given OBJECT of type pointer-to-structure, expands to the offset of MEMBER
+ * within an instance of the structure.
+ *
+ * The GCC-specific version avoids the technicality of undefined behavior if
+ * OBJECT is null, invalid, or not yet initialized. This makes some static
+ * checkers (like Coverity) happier. But the non-GCC version does not actually
+ * dereference any pointer, so it would be surprising for it to cause any
+ * problems in practice.
+ */
+#ifdef __GNUC__
+#define OBJECT_OFFSETOF(OBJECT, MEMBER) offsetof(typeof(*(OBJECT)), MEMBER)
+#else
+#define OBJECT_OFFSETOF(OBJECT, MEMBER) \
+ ((char *) &(OBJECT)->MEMBER - (char *) (OBJECT))
+#endif
+
/* Given POINTER, the address of the given MEMBER in a STRUCT object, returns
the STRUCT object. */
#define CONTAINER_OF(POINTER, STRUCT, MEMBER) \
@@ -99,7 +115,7 @@ extern const char *program_name;
* from the type of '*OBJECT'. */
#define OBJECT_CONTAINING(POINTER, OBJECT, MEMBER) \
((OVS_TYPEOF(OBJECT)) (void *) \
- ((char *) (POINTER) - ((char *) &(OBJECT)->MEMBER - (char *) (OBJECT))))
+ ((char *) (POINTER) - OBJECT_OFFSETOF(OBJECT, MEMBER)))
/* Given POINTER, the address of the given MEMBER within an object of the type
* that that OBJECT points to, assigns the address of the outer object to
--
1.7.2.3
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