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authorHaru <haru@dotalux.com>2015-12-27 17:35:25 +0100
committerHaru <haru@dotalux.com>2016-01-06 15:14:49 +0100
commita1b0dae953f0dde5f614f828710bcee78b5f2b78 (patch)
treede1c5b46a05ccb108c0a2555b2c5f83a615b729c
parent3007a376242f00d8127e39e9e6a89c7e0e5a8b20 (diff)
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Introduced the BL_UCAST() macro as an alternative to explicit casts
- The benefit of using BL_UCAST() instead of an explicit cast is that it produces a compiler error if the argument is not a block_list. - The benefit of using BL_UCAST() instead of BL_CAST() is that the block_list argument is guaranteed to be evaluated only once. As such it can be used in places where the argument is a function. - No block_list type checking is done. As such, if a different block_list type is passed, behavior is undefined. The user should do the checking beforehand. Signed-off-by: Haru <haru@dotalux.com>
-rw-r--r--src/map/map.h41
1 files changed, 40 insertions, 1 deletions
diff --git a/src/map/map.h b/src/map/map.h
index 7047feab6..f785ddc83 100644
--- a/src/map/map.h
+++ b/src/map/map.h
@@ -828,8 +828,47 @@ typedef struct homun_data TBL_HOM;
typedef struct mercenary_data TBL_MER;
typedef struct elemental_data TBL_ELEM;
+/**
+ * Casts a block list to a specific type.
+ *
+ * @remark
+ * The `bl` argument may be evaluated more than once.
+ *
+ * @param type_ The block list type (using symbols from enum bl_type).
+ * @param bl The source block list to cast.
+ * @return The block list, cast to the correct type.
+ * @retval NULL if bl is the wrong type or NULL.
+ */
#define BL_CAST(type_, bl) \
- ( ((bl) == (struct block_list*)NULL || (bl)->type != (type_)) ? (T ## type_ *)NULL : (T ## type_ *)(bl) )
+ ( ((bl) == (struct block_list *)NULL || (bl)->type != (type_)) ? (T ## type_ *)NULL : (T ## type_ *)(bl) )
+
+/**
+ * Helper function for `BL_UCAST`.
+ *
+ * @warning
+ * This function shouldn't be called on it own.
+ *
+ * The purpose of this function is to produce a compile-timer error if a non-bl
+ * object is passed to BL_UCAST. It's declared as static inline to let the
+ * compiler optimize out the function call overhead.
+ */
+static inline struct block_list *BL_UCAST_(struct block_list *bl)
+{
+ return bl;
+}
+
+/**
+ * Casts a block list to a specific type, without performing any type checks.
+ *
+ * @remark
+ * The `bl` argument is guaranteed to be evaluated once and only once.
+ *
+ * @param type_ The block list type (using symbols from enum bl_type).
+ * @param bl The source block list to cast.
+ * @return The block list, cast to the correct type.
+ */
+#define BL_UCAST(type_, bl) \
+ ((T ## type_ *)BL_UCAST_(bl))
struct charid_request {
struct charid_request* next;