{"id":3331,"date":"2025-03-29T17:17:16","date_gmt":"2025-03-29T09:17:16","guid":{"rendered":"https:\/\/www.laixuexila.com\/?p=3331"},"modified":"2025-03-29T17:17:16","modified_gmt":"2025-03-29T09:17:16","slug":"c-%e9%a2%84%e5%a4%84%e7%90%86%e5%99%a8-preprocessor","status":"publish","type":"post","link":"https:\/\/www.laixuexila.com\/index.php\/2025\/03\/29\/c-%e9%a2%84%e5%a4%84%e7%90%86%e5%99%a8-preprocessor\/","title":{"rendered":"C++ \u9884\u5904\u7406\u5668 (Preprocessor)"},"content":{"rendered":"\n<p>C++ \u9884\u5904\u7406\u5668\u662f\u5728\u7f16\u8bd1\u4e4b\u524d\u5bf9\u6e90\u4ee3\u7801\u8fdb\u884c\u5904\u7406\u7684\u5de5\u5177\u3002\u5b83\u8d1f\u8d23\u5904\u7406\u4ee3\u7801\u4e2d\u7684\u5b8f\u3001\u6587\u4ef6\u5305\u542b\u3001\u6761\u4ef6\u7f16\u8bd1\u7b49\u6307\u4ee4\u3002\u9884\u5904\u7406\u5668\u5e76\u4e0d\u76f4\u63a5\u7f16\u8bd1\u4ee3\u7801\uff0c\u800c\u662f\u5bf9\u4ee3\u7801\u8fdb\u884c\u9884\u5904\u7406\uff0c\u4ee5\u4fbf\u7f16\u8bd1\u5668\u80fd\u591f\u6b63\u786e\u5730\u89e3\u6790\u548c\u7f16\u8bd1\u6e90\u4ee3\u7801\u3002<\/p>\n\n\n\n<p>\u9884\u5904\u7406\u5668\u7684\u6307\u4ee4\u901a\u5e38\u4ee5 <code>#<\/code> \u5f00\u5934\uff0c\u4ee5\u4e0b\u662f C++ \u4e2d\u5e38\u7528\u7684\u9884\u5904\u7406\u5668\u6307\u4ee4\u3002<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>1. \u5b8f\u5b9a\u4e49 (<code>#define<\/code>)<\/strong><\/h2>\n\n\n\n<p>\u5b8f\u5b9a\u4e49\u7528\u4e8e\u5728\u7f16\u8bd1\u65f6\u66ff\u6362\u6e90\u4ee3\u7801\u4e2d\u7684\u67d0\u4e9b\u6587\u672c\u3002\u5b8f\u53ef\u4ee5\u662f\u5e38\u91cf\uff0c\u4e5f\u53ef\u4ee5\u662f\u51fd\u6570\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u5e38\u91cf\u5b8f<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define PI 3.14159  \/\/ \u5b9a\u4e49\u4e00\u4e2a\u5e38\u91cf\u5b8f\n\nint main() {\n    cout &lt;&lt; \"The value of PI is \" &lt;&lt; PI &lt;&lt; endl;\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>The value of PI is 3.14159<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u51fd\u6570\u5b8f<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define SQUARE(x) ((x) * (x))  \/\/ \u5b9a\u4e49\u4e00\u4e2a\u5b8f\u51fd\u6570\n\nint main() {\n    int result = SQUARE(5);  \/\/ \u4f7f\u7528\u5b8f\u51fd\u6570\n    cout &lt;&lt; \"The square of 5 is \" &lt;&lt; result &lt;&lt; endl;\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>The square of 5 is 25<\/code><\/pre>\n\n\n\n<p><strong>\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>#define<\/code> \u7528\u4e8e\u5b9a\u4e49\u5e38\u91cf\u6216\u5b8f\u51fd\u6570\u3002\u5b8f\u51fd\u6570\u5728\u8c03\u7528\u65f6\u4f1a\u8fdb\u884c\u66ff\u6362\uff0c\u7c7b\u4f3c\u4e8e\u6587\u672c\u66ff\u6362\u3002<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>2. \u6761\u4ef6\u7f16\u8bd1 (<code>#if<\/code>, <code>#else<\/code>, <code>#elif<\/code>, <code>#endif<\/code>)<\/strong><\/h2>\n\n\n\n<p>\u6761\u4ef6\u7f16\u8bd1\u5141\u8bb8\u6839\u636e\u7279\u5b9a\u7684\u6761\u4ef6\u6765\u51b3\u5b9a\u662f\u5426\u7f16\u8bd1\u67d0\u6bb5\u4ee3\u7801\u3002\u8fd9\u5728\u8de8\u5e73\u53f0\u5f00\u53d1\u6216\u8c03\u8bd5\u65f6\u7279\u522b\u6709\u7528\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u57fa\u672c\u6761\u4ef6\u7f16\u8bd1<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define DEBUG\n\nint main() {\n    #ifdef DEBUG  \/\/ \u5982\u679c\u5b9a\u4e49\u4e86 DEBUG\n        cout &lt;&lt; \"Debugging is enabled\" &lt;&lt; endl;\n    #else\n        cout &lt;&lt; \"Debugging is not enabled\" &lt;&lt; endl;\n    #endif\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Debugging is enabled<\/code><\/pre>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u5176\u4ed6\u6761\u4ef6\u7f16\u8bd1\u6307\u4ee4<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define VERSION 2\n\nint main() {\n    #if VERSION == 1\n        cout &lt;&lt; \"Version 1\" &lt;&lt; endl;\n    #elif VERSION == 2\n        cout &lt;&lt; \"Version 2\" &lt;&lt; endl;\n    #else\n        cout &lt;&lt; \"Unknown version\" &lt;&lt; endl;\n    #endif\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>Version 2<\/code><\/pre>\n\n\n\n<p><strong>\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>#ifdef<\/code>\u3001<code>#ifndef<\/code>\u3001<code>#if<\/code>\u3001<code>#elif<\/code>\u3001<code>#else<\/code> \u548c <code>#endif<\/code> \u5141\u8bb8\u5728\u7f16\u8bd1\u65f6\u6839\u636e\u7279\u5b9a\u6761\u4ef6\u6765\u7f16\u8bd1\u4e0d\u540c\u7684\u4ee3\u7801\u5757\u3002<\/li>\n\n\n\n<li><code>#ifdef<\/code>\uff1a\u5982\u679c\u5df2\u5b9a\u4e49\u67d0\u5b8f\uff0c\u7f16\u8bd1\u5bf9\u5e94\u7684\u4ee3\u7801\u3002<\/li>\n\n\n\n<li><code>#ifndef<\/code>\uff1a\u5982\u679c\u672a\u5b9a\u4e49\u67d0\u5b8f\uff0c\u7f16\u8bd1\u5bf9\u5e94\u7684\u4ee3\u7801\u3002<\/li>\n\n\n\n<li><code>#if<\/code>\uff1a\u6839\u636e\u6761\u4ef6\u8868\u8fbe\u5f0f\u7684\u503c\u6765\u7f16\u8bd1\u4ee3\u7801\u3002<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>3. \u6587\u4ef6\u5305\u542b (<code>#include<\/code>)<\/strong><\/h2>\n\n\n\n<p><code>#include<\/code> \u6307\u4ee4\u7528\u4e8e\u5c06\u5916\u90e8\u6587\u4ef6\u7684\u5185\u5bb9\u63d2\u5165\u5230\u5f53\u524d\u6e90\u6587\u4ef6\u4e2d\u3002\u901a\u5e38\u7528\u6765\u5f15\u5165\u5934\u6587\u4ef6\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u7cfb\u7edf\u5934\u6587\u4ef6\u4e0e\u81ea\u5b9a\u4e49\u5934\u6587\u4ef6<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;  \/\/ \u7cfb\u7edf\u5934\u6587\u4ef6\n#include \"myheader.h\"  \/\/ \u81ea\u5b9a\u4e49\u5934\u6587\u4ef6\n\nint main() {\n    cout &lt;&lt; \"Hello, World!\" &lt;&lt; endl;\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>#include &lt;filename><\/code> \u7528\u4e8e\u5f15\u5165\u6807\u51c6\u5e93\u7684\u5934\u6587\u4ef6\u3002<\/li>\n\n\n\n<li><code>#include \"filename\"<\/code> \u7528\u4e8e\u5f15\u5165\u81ea\u5b9a\u4e49\u7684\u5934\u6587\u4ef6\uff0c\u7f16\u8bd1\u5668\u4f1a\u9996\u5148\u5728\u5f53\u524d\u76ee\u5f55\u67e5\u627e\u8be5\u6587\u4ef6\u3002<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>4. \u5b8f\u53d6\u6d88 (<code>#undef<\/code>)<\/strong><\/h2>\n\n\n\n<p><code>#undef<\/code> \u7528\u4e8e\u53d6\u6d88\u5148\u524d\u5b9a\u4e49\u7684\u5b8f\u3002\u5982\u679c\u4e00\u4e2a\u5b8f\u4e0d\u518d\u9700\u8981\uff0c\u4f7f\u7528 <code>#undef<\/code> \u53ef\u4ee5\u53d6\u6d88\u5b83\u7684\u5b9a\u4e49\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define PI 3.14159\n#undef PI  \/\/ \u53d6\u6d88\u5b9a\u4e49 PI\n\nint main() {\n    \/\/ cout &lt;&lt; \"PI is \" &lt;&lt; PI &lt;&lt; endl;  \/\/ \u8fd9\u91cc PI \u5df2\u7ecf\u672a\u5b9a\u4e49\uff0c\u7f16\u8bd1\u5668\u4f1a\u62a5\u9519\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>#undef<\/code> \u7528\u4e8e\u53d6\u6d88\u5b8f\u7684\u5b9a\u4e49\uff0c\u4f7f\u5176\u5728\u540e\u7eed\u4ee3\u7801\u4e2d\u4e0d\u53ef\u7528\u3002<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>5. \u5b8f\u66ff\u6362\u89c4\u5219<\/strong><\/h2>\n\n\n\n<p>\u5728\u4f7f\u7528\u5b8f\u65f6\uff0c\u9884\u5904\u7406\u5668\u5c06\u5b8f\u7684\u540d\u79f0\u76f4\u63a5\u66ff\u6362\u4e3a\u5b9a\u4e49\u7684\u5185\u5bb9\u3002\u5728\u66ff\u6362\u65f6\u9700\u8981\u6ce8\u610f\u4f18\u5148\u7ea7\u548c\u62ec\u53f7\u95ee\u9898\uff0c\u907f\u514d\u9519\u8bef\u7684\u8ba1\u7b97\u7ed3\u679c\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u5b8f\u66ff\u6362\u95ee\u9898<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define SQUARE(x) x * x\n\nint main() {\n    int result = SQUARE(5 + 1);\n    cout &lt;&lt; \"The result is \" &lt;&lt; result &lt;&lt; endl;  \/\/ \u7ed3\u679c\u662f 5 + 1 * 5 + 1\uff0c\u5373 11\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>The result is 11<\/code><\/pre>\n\n\n\n<p><strong>\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>SQUARE(5 + 1)<\/code> \u5728\u9884\u5904\u7406\u65f6\u4f1a\u88ab\u66ff\u6362\u4e3a <code>5 + 1 * 5 + 1<\/code>\uff0c\u8fd9\u5e76\u4e0d\u662f\u6211\u4eec\u671f\u671b\u7684 <code>(5 + 1) * (5 + 1)<\/code>\uff0c\u56e0\u4e3a\u6ca1\u6709\u52a0\u4e0a\u5fc5\u8981\u7684\u62ec\u53f7\u3002<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u6539\u6b63\u65b9\u5f0f<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\n#define SQUARE(x) ((x) * (x))  \/\/ \u6dfb\u52a0\u62ec\u53f7\u6765\u907f\u514d\u4f18\u5148\u7ea7\u95ee\u9898\n\nint main() {\n    int result = SQUARE(5 + 1);  \/\/ \u7ed3\u679c\u662f (5 + 1) * (5 + 1)\n    cout &lt;&lt; \"The result is \" &lt;&lt; result &lt;&lt; endl;  \/\/ \u7ed3\u679c\u662f 36\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>The result is 36<\/code><\/pre>\n\n\n\n<p><strong>\u8bf4\u660e\uff1a<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>\u4f7f\u7528\u62ec\u53f7\u5305\u88f9\u5b8f\u7684\u53c2\u6570\u548c\u6574\u4e2a\u5b8f\u66ff\u6362\u8868\u8fbe\u5f0f\uff0c\u786e\u4fdd\u6b63\u786e\u7684\u4f18\u5148\u7ea7\u548c\u8fd0\u7b97\u987a\u5e8f\u3002<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>6. \u9884\u5b9a\u4e49\u5b8f<\/strong><\/h2>\n\n\n\n<p>C++ \u9884\u5904\u7406\u5668\u8fd8\u5b9a\u4e49\u4e86\u4e00\u4e9b\u9884\u8bbe\u7684\u5b8f\uff0c\u5982\u4e0b\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>__DATE__<\/code>\uff1a\u5f53\u524d\u65e5\u671f\uff08\u5b57\u7b26\u4e32\u683c\u5f0f\uff1a<code>\"Mmm dd yyyy\"<\/code>\uff09<\/li>\n\n\n\n<li><code>__TIME__<\/code>\uff1a\u5f53\u524d\u65f6\u95f4\uff08\u5b57\u7b26\u4e32\u683c\u5f0f\uff1a<code>\"hh:mm:ss\"<\/code>\uff09<\/li>\n\n\n\n<li><code>__FILE__<\/code>\uff1a\u5f53\u524d\u6587\u4ef6\u540d\uff08\u5b57\u7b26\u4e32\u683c\u5f0f\uff09<\/li>\n\n\n\n<li><code>__LINE__<\/code>\uff1a\u5f53\u524d\u884c\u53f7\uff08\u6574\u6570\uff09<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u793a\u4f8b<\/strong><\/h3>\n\n\n\n<pre class=\"wp-block-code\"><code>#include &lt;iostream&gt;\nusing namespace std;\n\nint main() {\n    cout &lt;&lt; \"File: \" &lt;&lt; __FILE__ &lt;&lt; endl;\n    cout &lt;&lt; \"Line: \" &lt;&lt; __LINE__ &lt;&lt; endl;\n    cout &lt;&lt; \"Date: \" &lt;&lt; __DATE__ &lt;&lt; endl;\n    cout &lt;&lt; \"Time: \" &lt;&lt; __TIME__ &lt;&lt; endl;\n    return 0;\n}<\/code><\/pre>\n\n\n\n<p><strong>\u8f93\u51fa\uff1a<\/strong><\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>File: main.cpp\nLine: 10\nDate: Mar 29 2025\nTime: 14:03:12<\/code><\/pre>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>7. \u5c0f\u7ed3<\/strong><\/h2>\n\n\n\n<p>C++ \u9884\u5904\u7406\u5668\u63d0\u4f9b\u4e86\u4e00\u7cfb\u5217\u5f3a\u5927\u7684\u529f\u80fd\u6765\u5904\u7406\u4ee3\u7801\u7684\u9884\u7f16\u8bd1\u8fc7\u7a0b\uff0c\u5982\u5b8f\u5b9a\u4e49\u3001\u6761\u4ef6\u7f16\u8bd1\u3001\u6587\u4ef6\u5305\u542b\u3001\u53d6\u6d88\u5b8f\u5b9a\u4e49\u7b49\u3002\u901a\u8fc7\u5408\u7406\u4f7f\u7528\u9884\u5904\u7406\u5668\u6307\u4ee4\uff0c\u53ef\u4ee5\u63d0\u9ad8\u4ee3\u7801\u7684\u53ef\u7ef4\u62a4\u6027\u3001\u7075\u6d3b\u6027\uff0c\u5e76\u89e3\u51b3\u8de8\u5e73\u53f0\u7f16\u7a0b\u4e2d\u7684\u95ee\u9898\u3002<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>\u5e38\u89c1\u9884\u5904\u7406\u5668\u6307\u4ee4\u603b\u7ed3\uff1a<\/strong><\/h3>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>#define<\/code>\uff1a\u5b9a\u4e49\u5b8f\u5e38\u91cf\u6216\u5b8f\u51fd\u6570<\/li>\n\n\n\n<li><code>#undef<\/code>\uff1a\u53d6\u6d88\u5b8f\u5b9a\u4e49<\/li>\n\n\n\n<li><code>#include<\/code>\uff1a\u5305\u542b\u5934\u6587\u4ef6<\/li>\n\n\n\n<li><code>#if<\/code>, <code>#else<\/code>, <code>#elif<\/code>, <code>#endif<\/code>\uff1a\u6761\u4ef6\u7f16\u8bd1<\/li>\n\n\n\n<li><code>#ifdef<\/code>, <code>#ifndef<\/code>\uff1a\u5224\u65ad\u5b8f\u662f\u5426\u5df2\u5b9a\u4e49<\/li>\n\n\n\n<li><code>__DATE__<\/code>, <code>__TIME__<\/code>, <code>__FILE__<\/code>, <code>__LINE__<\/code>\uff1a\u9884\u5b9a\u4e49\u5b8f<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>C++ \u9884\u5904\u7406\u5668\u662f\u5728\u7f16\u8bd1\u4e4b\u524d\u5bf9\u6e90\u4ee3\u7801\u8fdb\u884c\u5904\u7406\u7684\u5de5\u5177\u3002\u5b83\u8d1f\u8d23\u5904\u7406\u4ee3\u7801\u4e2d\u7684\u5b8f\u3001\u6587\u4ef6\u5305\u542b\u3001\u6761\u4ef6\u7f16\u8bd1\u7b49\u6307\u4ee4\u3002\u9884\u5904\u7406\u5668\u5e76 [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":3332,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[81],"tags":[],"class_list":["post-3331","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-c-"],"_links":{"self":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3331","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/comments?post=3331"}],"version-history":[{"count":1,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3331\/revisions"}],"predecessor-version":[{"id":3333,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/posts\/3331\/revisions\/3333"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media\/3332"}],"wp:attachment":[{"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/media?parent=3331"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/categories?post=3331"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.laixuexila.com\/index.php\/wp-json\/wp\/v2\/tags?post=3331"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}