eal: fix container_of macro for const members

[dpdk.git] / lib / librte_eal / common / include / rte_common.h

diff --git a/lib/librte_eal/common/include/rte_common.h b/lib/librte_eal/common/include/rte_common.h
index 98ecc1c..c421708 100644 (file)
--- a/lib/librte_eal/common/include/rte_common.h
+++ b/lib/librte_eal/common/include/rte_common.h
@@ -331,10 +331,40 @@ rte_bsf32(uint32_t v)
 #define offsetof(TYPE, MEMBER)  __builtin_offsetof (TYPE, MEMBER)
 #endif
 
+/**
+ * Return pointer to the wrapping struct instance.
+ *
+ * Example:
+ *
+ *  struct wrapper {
+ *      ...
+ *      struct child c;
+ *      ...
+ *  };
+ *
+ *  struct child *x = obtain(...);
+ *  struct wrapper *w = container_of(x, struct wrapper, c);
+ */
+#ifndef container_of
+#define container_of(ptr, type, member)        __extension__ ({                \
+                       const typeof(((type *)0)->member) *_ptr = (ptr); \
+                       (type *)(((uintptr_t)_ptr) - offsetof(type, member)); \
+               })
+#endif
+
 #define _RTE_STR(x) #x
 /** Take a macro value and get a string version of it */
 #define RTE_STR(x) _RTE_STR(x)
 
+/**
+ * ISO C helpers to modify format strings using variadic macros.
+ * This is a replacement for the ", ## __VA_ARGS__" GNU extension.
+ * An empty %s argument is appended to avoid a dangling comma.
+ */
+#define RTE_FMT(fmt, ...) fmt "%.0s", __VA_ARGS__ ""
+#define RTE_FMT_HEAD(fmt, ...) fmt
+#define RTE_FMT_TAIL(fmt, ...) __VA_ARGS__
+
 /** Mask value of type "tp" for the first "ln" bit set. */
 #define        RTE_LEN2MASK(ln, tp)    \
        ((tp)((uint64_t)-1 >> (sizeof(uint64_t) * CHAR_BIT - (ln))))