{"id":840,"date":"2026-04-22T14:44:30","date_gmt":"2026-04-22T06:44:30","guid":{"rendered":"https:\/\/hsiang.cc\/?p=840"},"modified":"2026-04-20T14:53:21","modified_gmt":"2026-04-20T06:53:21","slug":"c-%e7%9a%84%e9%82%a3%e4%ba%9b%e7%9c%89%e8%a7%92define-%e7%9a%84%e9%99%b7%e9%98%b1-%e6%b2%92%e7%94%a8%e5%a5%bd%e6%9c%83%e6%8e%89%e9%80%b2%e5%9d%91","status":"publish","type":"post","link":"https:\/\/hsiang.cc\/?p=840","title":{"rendered":"[C \u7684\u90a3\u4e9b\u7709\u89d2]#define \u7684\u9677\u9631 \u2014 \u6c92\u7528\u597d\u6703\u6389\u9032\u5751"},"content":{"rendered":"

#define<\/code> \u53ef\u4ee5\u8aaa\u662f C \u8a9e\u8a00\u88e1\u6700\u65e9\u5b78\u5230\u7684\u6771\u897f\u4e4b\u4e00\u3002<\/p>\n

#define MAX_SIZE 256\n#define PI 3.14159<\/code><\/pre>\n
\u770b\u8d77\u4f86\u5f88\u7121\u5bb3\uff0c\u5c0d\u5427\uff1f<\/p>\n
\u4f46\u7528\u4e45\u4e86\u624d\u767c\u73fe\uff0c#define<\/code> \u5176\u5be6\u662f\u500b\u5f88\u5bb9\u6613\u51fa\u4e8b\u7684\u5de5\u5177\u3002
\n\u5b83\u4e0d\u662f\u8b8a\u6578\u3001\u4e0d\u662f\u51fd\u5f0f\u3001\u4e0d\u9075\u5b88 scope\u3001\u4e0d\u505a\u578b\u5225\u6aa2\u67e5\uff0c
\n\u5c31\u662f\u55ae\u7d14\u7684\u6587\u5b57\u66ff\u63db\u3002<\/p>\n
\u800c\u300c\u55ae\u7d14\u7684\u6587\u5b57\u66ff\u63db\u300d\uff0c\u5728\u67d0\u4e9b\u60c5\u6cc1\u4e0b\u6703\u7522\u751f\u4f60\u5b8c\u5168\u6c92\u9810\u671f\u5230\u7684\u7d50\u679c\u3002<\/p>\n
\u9019\u7bc7\u8a18\u9304\u5e7e\u500b\u6211\u81ea\u5df1\u8e29\u904e\u3001\u6216\u5728 code review \u770b\u904e\u7684\u5751\u3002<\/p>\n
<\/p>\n
\n
\u5751 #1\uff1aMacro \u904b\u7b97\u5f0f\u6c92\u52a0\u62ec\u865f<\/h2>\n
\u9019\u662f\u6700\u7d93\u5178\u7684\uff0c\u4f46\u9084\u662f\u4e00\u76f4\u6709\u4eba\u8e29\u3002<\/p>\n
#define SQUARE(x)  x * x<\/code><\/pre>\n
\u770b\u8d77\u4f86\u6c92\u554f\u984c\uff0c\u4f46\uff1a<\/p>\n
int result = SQUARE(3 + 1);<\/code><\/pre>\n
\u5c55\u958b\u4e4b\u5f8c\u8b8a\u6210\uff1a<\/p>\n
int result = 3 + 1 * 3 + 1;  \/\/ = 7\uff0c\u4e0d\u662f 16<\/code><\/pre>\n
\u56e0\u70ba preprocessor \u53ea\u662f\u505a\u6587\u5b57\u66ff\u63db\uff0c\u4e0d\u7ba1\u904b\u7b97\u5b50\u512a\u5148\u9806\u5e8f\u3002<\/p>\n
\u6b63\u78ba\u5beb\u6cd5\u662f\u6bcf\u500b\u53c3\u6578\u3001\u6574\u500b\u904b\u7b97\u5f0f\u90fd\u52a0\u62ec\u865f\uff1a<\/p>\n
#define SQUARE(x)  ((x) * (x))<\/code><\/pre>\n
\u5c55\u958b\u5f8c\uff1a<\/p>\n
int result = ((3 + 1) * (3 + 1));  \/\/ = 16 \u2705<\/code><\/pre>\n
\u539f\u5247\uff1aMacro \u7684\u53c3\u6578\u548c\u6574\u9ad4\uff0c\u5168\u90e8\u90fd\u52a0\u62ec\u865f\u3002<\/strong><\/p>\n
\n
\u5751 #2\uff1a\u53c3\u6578\u6709\u526f\u4f5c\u7528\uff0c\u88ab\u5c55\u958b\u5169\u6b21<\/h2>\n
\u62ec\u865f\u52a0\u597d\u4e86\uff0c\u4f46\u9084\u6709\u53e6\u4e00\u500b\u554f\u984c\uff1a<\/p>\n
#define SQUARE(x)  ((x) * (x))\n\nint i = 3;\nint result = SQUARE(i++);<\/code><\/pre>\n
\u5c55\u958b\u5f8c\uff1a<\/p>\n
int result = ((i++) * (i++));<\/code><\/pre>\n
i++<\/code> \u88ab\u57f7\u884c\u4e86\u5169\u6b21\u3002<\/p>\n
\u7d50\u679c\u662f undefined behavior\uff0c\u4e0d\u540c\u7de8\u8b6f\u5668\u3001\u4e0d\u540c\u512a\u5316\u7b49\u7d1a\uff0c
\n\u8dd1\u51fa\u4f86\u7684\u7d50\u679c\u53ef\u80fd\u90fd\u4e0d\u4e00\u6a23\u3002<\/p>\n
\u9019\u7a2e bug \u5f88\u96e3\u627e\uff0c\u56e0\u70ba\u4f60\u6839\u672c\u4e0d\u6703\u53bb\u61f7\u7591\u4e00\u500b\u300c\u770b\u8d77\u4f86\u50cf\u51fd\u5f0f\u300d\u7684\u6771\u897f
\n\u6703\u628a\u53c3\u6578\u5c55\u958b\u5169\u6b21\u3002<\/p>\n
\u539f\u5247\uff1a\u6709\u526f\u4f5c\u7528\u7684\u904b\u7b97\u5f0f\uff08i++<\/code>\u3001\u51fd\u5f0f\u547c\u53eb\uff09\u4e0d\u8981\u50b3\u9032 Macro\u3002<\/strong><\/p>\n
\n
\u5751 #3\uff1a\u591a\u884c Macro \u6c92\u7528 do { } while(0)<\/code><\/h2>\n
\u6709\u6642\u5019 Macro \u6703\u5305\u542b\u591a\u884c\u7a0b\u5f0f\u78bc\uff1a<\/p>\n
#define RESET_DEVICE()  \\\n    gpio_set_low(RESET_PIN);  \\\n    delay_ms(10);             \\\n    gpio_set_high(RESET_PIN);<\/code><\/pre>\n
\u9019\u6a23\u5beb\u5728\u5927\u90e8\u5206\u60c5\u6cc1\u4e0b\u6c92\u554f\u984c\uff0c\u4f46\u9047\u5230 if\/else \u5c31\u7206\u4e86\uff1a<\/p>\n
if (error)\n    RESET_DEVICE();\nelse\n    do_something();<\/code><\/pre>\n
\u5c55\u958b\u5f8c\uff1a<\/p>\n
if (error)\n    gpio_set_low(RESET_PIN);\n    delay_ms(10);              \/\/ \u9019\u884c\u6c38\u9060\u57f7\u884c\uff01\n    gpio_set_high(RESET_PIN);  \/\/ \u9019\u884c\u4e5f\u662f\uff01\nelse                           \/\/ \u9019\u500b else \u627e\u4e0d\u5230\u5c0d\u61c9\u7684 if\uff0c\u7de8\u8b6f\u932f\u8aa4\n    do_something();<\/code><\/pre>\n
\u6b63\u78ba\u5beb\u6cd5\u662f\u7528 do { } while(0)<\/code> \u5305\u8d77\u4f86\uff1a<\/p>\n
#define RESET_DEVICE()        \\\n    do {                      \\\n        gpio_set_low(RESET_PIN);  \\\n        delay_ms(10);             \\\n        gpio_set_high(RESET_PIN); \\\n    } while(0)<\/code><\/pre>\n
\u9019\u6a23\u4e0d\u7ba1\u5728\u4ec0\u9ebc\u60c5\u6cc1\u4e0b\u4f7f\u7528\uff0c\u884c\u70ba\u90fd\u662f\u6b63\u78ba\u7684\uff0c
\n\u800c\u4e14\u7d50\u5c3e\u7684\u5206\u865f\u4e5f\u4e0d\u6703\u51fa\u554f\u984c\u3002<\/p>\n
\u7b2c\u4e00\u6b21\u770b\u5230\u9019\u500b\u5beb\u6cd5\u7684\u6642\u5019\u89ba\u5f97\u5f88\u5947\u602a\uff0c
\n\u5f8c\u4f86\u624d\u7406\u89e3\u9019\u662f C \u8a9e\u8a00\u7684\u6163\u7528\u6a21\u5f0f\u3002<\/p>\n
\n
\u5751 #4\uff1aMacro \u540d\u7a31\u8ddf\u8b8a\u6578\u649e\u540d<\/h2>\n
#define<\/code> \u4e0d\u7ba1 scope\uff0c\u6574\u500b translation unit \u90fd\u6709\u6548\u3002<\/p>\n
#define SIZE 10\n\nvoid some_function(void) {\n    int SIZE = get_buffer_size();  \/\/ \u7de8\u8b6f\u932f\u8aa4\u6216\u5947\u602a\u7684\u884c\u70ba\n    ...\n}<\/code><\/pre>\n
preprocessor \u6703\u628a SIZE<\/code> \u76f4\u63a5\u63db\u6210 10<\/code>\uff0c
\n\u6240\u4ee5\u4e0a\u9762\u90a3\u884c\u8b8a\u6210 int 10 = get_buffer_size();<\/code>\uff0c
\n\u76f4\u63a5\u7de8\u8b6f\u932f\u8aa4\u3002<\/p>\n
\u9019\u500b\u9084\u7b97\u5bb9\u6613\u767c\u73fe\u3002\u66f4\u96e3\u767c\u73fe\u7684\u662f\uff1a<\/p>\n
#define MAX 100\n\n\/\/ \u67d0\u500b\u7b2c\u4e09\u65b9 library \u7684 header\ntypedef struct {\n    int max;   \/\/ \u9019\u500b max \u6c92\u4e8b\n    int MAX;   \/\/ \u9019\u500b\u6703\u88ab\u5c55\u958b\u6210 int 100\uff0c\u7de8\u8b6f\u932f\u8aa4\n} Config;<\/code><\/pre>\n
include \u9806\u5e8f\u4e0d\u540c\uff0c\u7d50\u679c\u5c31\u4e0d\u540c\uff0c\u5f88\u96e3 debug\u3002<\/p>\n
\u539f\u5247\uff1aMacro \u540d\u7a31\u5168\u5927\u5beb\u52a0\u5e95\u7dda\uff0c\u6e1b\u5c11\u649e\u540d\u6a5f\u6703\u3002<\/strong>
\n\u539f\u5247\uff1a\u80fd\u7528 const<\/code> \u6216 enum<\/code> \u7684\u5730\u65b9\uff0c\u5c31\u4e0d\u8981\u7528 #define<\/code>\u3002<\/strong><\/p>\n
\n
\u4ec0\u9ebc\u6642\u5019\u8a72\u7528 const<\/code> \u53d6\u4ee3 #define<\/code><\/h2>\n
\u5b9a\u7fa9\u5e38\u6578\u7684\u6642\u5019\uff0cconst<\/code> \u6bd4 #define<\/code> \u597d\u5f88\u591a\uff1a<\/p>\n
\/\/ \u274c #define \u7248\u672c\n#define MAX_RETRY_COUNT  3\n#define TIMEOUT_MS       5000\n\n\/\/ \u2705 const \u7248\u672c\nconst int MAX_RETRY_COUNT = 3;\nconst uint32_t TIMEOUT_MS = 5000;<\/code><\/pre>\n
const<\/code> \u7684\u597d\u8655\uff1a<\/p>\n