Posted on 2013-03-26 15:26
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網(wǎng)絡編程
ACE源碼
OS_Memory.h是這樣定義的。
# if defined (ACE_HAS_NEW_NOTHROW)
# define ACE_NEW_RETURN(POINTER,CONSTRUCTOR,RET_VAL) \
do { POINTER = new (ACE_nothrow) CONSTRUCTOR; \
if (POINTER == 0) { errno = ENOMEM; return RET_VAL; } \
} while (0)
# define ACE_NEW(POINTER,CONSTRUCTOR) \
do { POINTER = new(ACE_nothrow) CONSTRUCTOR; \
if (POINTER == 0) { errno = ENOMEM; return; } \
} while (0)
# define ACE_NEW_NORETURN(POINTER,CONSTRUCTOR) \
do { POINTER = new(ACE_nothrow) CONSTRUCTOR; \
if (POINTER == 0) { errno = ENOMEM; } \
} while (0)
# else
# define ACE_NEW_RETURN(POINTER,CONSTRUCTOR,RET_VAL) \
do { try { POINTER = new CONSTRUCTOR; } \
catch (ACE_bad_alloc) { ACE_del_bad_alloc errno = ENOMEM; POINTER = 0; return RET_VAL; } \
} while (0)
# define ACE_NEW(POINTER,CONSTRUCTOR) \
do { try { POINTER = new CONSTRUCTOR; } \
catch (ACE_bad_alloc) { ACE_del_bad_alloc errno = ENOMEM; POINTER = 0; return; } \
} while (0)
# define ACE_NEW_NORETURN(POINTER,CONSTRUCTOR) \
do { try { POINTER = new CONSTRUCTOR; } \
catch (ACE_bad_alloc) { ACE_del_bad_alloc errno = ENOMEM; POINTER = 0; } \
} while (0)
# endif /* ACE_HAS_NEW_NOTHROW */
#else /* ACE_NEW_THROWS_EXCEPTIONS */
# define ACE_NEW_RETURN(POINTER,CONSTRUCTOR,RET_VAL) \
do { POINTER = new CONSTRUCTOR; \
if (POINTER == 0) { errno = ENOMEM; return RET_VAL; } \
} while (0)
# define ACE_NEW(POINTER,CONSTRUCTOR) \
do { POINTER = new CONSTRUCTOR; \
if (POINTER == 0) { errno = ENOMEM; return; } \
} while (0)
# define ACE_NEW_NORETURN(POINTER,CONSTRUCTOR) \
do { POINTER = new CONSTRUCTOR; \
if (POINTER == 0) { errno = ENOMEM; } \
} while (0)
以上是用宏定義替換的表達式，功能都是用一個POINTER指針new一個CONSTRUCTOR實例，內(nèi)部做了一些錯誤信息的標志和異常處理。
宏ifelse對平臺的不同進行了分離，每個平臺下都有三種new的方法，他們的區(qū)別是return。
每個宏定義都用到了do{}while(0)，是因為宏只能替換一句表達式，而你用do{}while(0)可以方便的把多個表達式集中起來。