{"id":420416,"date":"2023-12-18T10:33:09","date_gmt":"2023-12-18T09:33:09","guid":{"rendered":"https:\/\/blog.jetbrains.com\/?post_type=clion&#038;p=420416"},"modified":"2023-12-21T07:46:18","modified_gmt":"2023-12-21T06:46:18","slug":"striving-for-better-cpp-code-part-i-data-flow-analysis-basics","status":"publish","type":"clion","link":"https:\/\/blog.jetbrains.com\/zh-hans\/clion\/2023\/12\/striving-for-better-cpp-code-part-i-data-flow-analysis-basics\/","title":{"rendered":"\u52aa\u529b\u83b7\u5f97\u66f4\u597d\u7684 C++ \u4ee3\u7801\uff0c\u7b2c\u4e00\u90e8\u5206\uff1a\u6570\u636e\u6d41\u5206\u6790\u57fa\u7840\u77e5\u8bc6"},"content":{"rendered":"<p>CLion \u63d0\u4f9b\u4e86\u4e00\u4e2a\u5185\u7f6e\u6570\u636e\u6d41\u5206\u6790\u5668\uff0c\u5b83\u4f1a\u5728\u60a8\u7f16\u5199\u4ee3\u7801\u65f6\u6301\u7eed\u8fd0\u884c\u5e76\u5e2e\u52a9\u63d0\u9ad8\u4ee3\u7801\u8d28\u91cf\u3002 \u5b83\u53ef\u4ee5\u663e\u793a\u5404\u79cd<a href=\"https:\/\/www.jetbrains.com.cn\/help\/clion\/global-dataflow-analysis.html\" target=\"_blank\" rel=\"noopener\">\u4ee3\u7801\u95ee\u9898<\/a>\uff0c\u8fd9\u4e9b\u95ee\u9898\u968f\u540e\u53ef\u80fd\u5bfc\u81f4\u8fd0\u884c\u65f6\u95ee\u9898\u3001\u5b89\u5168\u6f0f\u6d1e\u548c\u5176\u4ed6\u6f0f\u6d1e\u3002 \u4e3e\u4f8b\u6765\u8bf4\uff0c\u8fd9\u4e9b\u6709\u7528\u7684\u68c0\u67e5\u5305\u62ec\u5e38\u91cf\u6761\u4ef6\u3001\u6b7b\u4ee3\u7801\u3001null \u6307\u9488\u53d6\u6d88\u5f15\u7528\u3001\u5185\u5b58\u6cc4\u6f0f\u548c\u6570\u7ec4\u7d22\u5f15\u95ee\u9898\u3002 \u6211\u4eec\u5c06\u53d1\u5e03\u4e00\u7cfb\u5217\u535a\u6587\u6765\u8bf4\u660e CLion \u4e2d\u67d0\u4e9b\u68c0\u67e5\u7684\u8fd0\u4f5c\u65b9\u5f0f\u3002<\/p>\n<p>\u4eca\u5929\uff0c\u6211\u4eec\u5c06\u4ecb\u7ecd\u6570\u636e\u6d41\u5206\u6790\u7684\u57fa\u7840\u77e5\u8bc6\uff0c\u5305\u62ec\u5b83\u7684\u4e00\u822c\u8fd0\u4f5c\u65b9\u5f0f\uff0c\u540c\u65f6\u4ecb\u7ecd\u51e0\u4e2a\u771f\u5b9e\u7684\u4f8b\u5b50\uff0c\u4ee5\u5e2e\u52a9\u60a8\u7f16\u5199\u51fa\u66f4\u597d\u7684\u4ee3\u7801\u3002<\/p>\n<h2 id=\"control_flow_graph\">\u63a7\u5236\u6d41\u56fe<\/h2>\n<p>\u6240\u6709\u6570\u636e\u6d41\u68c0\u67e5\u90fd\u4f9d\u8d56\u4e8e<a href=\"https:\/\/en.wikipedia.org\/wiki\/Control-flow_graph\" target=\"_blank\" rel=\"noopener\">\u63a7\u5236\u6d41\u56fe<\/a>\u3002 \u5b83\u662f\u4e00\u4e2a\u56fe\u8868\uff0c\u5176\u4e2d\u9876\u70b9\u662f\u7a0b\u5e8f\u4e2d\u7684\u8bed\u53e5\uff0c\u8fb9\u662f\u8fd9\u4e9b\u8bed\u53e5\u4e4b\u95f4\u7684\u63a7\u5236\u6d41\u8df3\u8f6c\uff08\u76f4\u63a5\u4ee3\u7801\u6267\u884c\u3001\u6761\u4ef6\u8df3\u8f6c\u3001\u5faa\u73af\u3001\u4e2d\u65ad\u3001\u8f6c\u5230\u7b49\uff09\u3002<\/p>\n<p>\u4f8b\u5982\uff0c\u53f3\u4fa7\u7684\u63a7\u5236\u6d41\u56fe\u8868\u793a\u5de6\u4fa7\u7684 <code>foo<\/code> \u51fd\u6570\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2023\/10\/basic_sample_scheme.png\" alt=\"\u57fa\u672c\u793a\u4f8b\" width=\"513\" \/><\/p>\n<p>CLion \u4f1a\u4e3a\u6bcf\u4e2a\u51fd\u6570\u6784\u5efa\u76f8\u5e94\u7684\u56fe\u3002 \u6bcf\u4e2a\u56fe\u90fd\u6709\u4e00\u4e2a\u5f00\u59cb\u8282\u70b9\u548c\u4e00\u4e2a\u9000\u51fa\u8282\u70b9\uff0c\u5b83\u4eec\u5bf9\u5e94\u4e8e\u51fd\u6570\u7684\u5165\u53e3\u548c\u51fa\u53e3\u3002 \u901a\u8fc7\u8bbf\u95ee\u4ece\u5f00\u59cb\u8282\u70b9\u5230\u9000\u51fa\u8282\u70b9\u7684\u56fe\u8282\u70b9\uff0cCLion \u53ef\u4ee5\u6536\u96c6\u4e00\u4e9b\u6709\u4ef7\u503c\u7684\u4fe1\u606f\u3002<\/p>\n<p>\u4f8b\u5982\uff0cCLion \u4f1a\u8bb0\u4f4f\u6bcf\u6761\u8bed\u53e5\u7684\u6bcf\u4e2a\u53d8\u91cf\u4e2d\u53ef\u4ee5\u5b58\u50a8\u54ea\u4e9b\u503c\u3002 \u5728\u4e0a\u8ff0\u793a\u4f8b\u4e2d\uff0cCLion \u77e5\u9053\u5728\u8282\u70b9 0 \u548c 1 \u5904\uff0c\u5f62\u53c2 <code>x<\/code> \u59cb\u7ec8\u7b49\u4e8e 1\u3002 \u8fd9\u662f\u56e0\u4e3a\u51fd\u6570 <code>foo<\/code> \u53ea\u6709\u4e00\u4e2a\u8c03\u7528\u70b9\uff0c\u5b83\u4f1a\u4f20\u9012\u5b9e\u53c2\u4e2d\u7684\u503c 1\u3002 \u56e0\u6b64\uff0cCLion \u5f97\u51fa\u7ed3\u8bba\uff0c\u8282\u70b9 <strong>1<\/strong> \u5904\u7684\u6761\u4ef6 <code>x == 1<\/code> \u5c06\u59cb\u7ec8\u4e3a <code>true<\/code>\uff0c\u56e0\u6b64\u63a7\u5236\u6d41\u6c38\u8fdc\u4e0d\u4f1a\u5230\u8fbe\u8282\u70b9 <strong>3<\/strong>\u3002 \u5728\u8282\u70b9 <strong>4<\/strong> \u5904\uff0c\u53d8\u91cf <strong>y<\/strong> \u53ea\u80fd\u4fdd\u5b58\u503c <strong>2<\/strong>\uff0c\u56e0\u4e3a\u63a7\u5236\u6d41\u53ea\u80fd\u6765\u81ea\u8282\u70b9 <strong>2<\/strong>\uff0c\u6c38\u8fdc\u4e0d\u4f1a\u6765\u81ea\u8282\u70b9 <strong>3<\/strong>\u3002 \u56e0\u6b64\uff0cCLion \u5f97\u51fa\u7ed3\u8bba\uff1a<\/p>\n<ol>\n<li>\u51fd\u6570 <code>foo<\/code> \u59cb\u7ec8\u8fd4\u56de\u503c <strong>2<\/strong><\/li>\n<li>\u6761\u4ef6 <code>x == 1<\/code> \u59cb\u7ec8\u4e3a <code>true<\/code><\/li>\n<li>\u8bed\u53e5 <code>y = 3<\/code> \u6c38\u8fdc\u65e0\u6cd5\u8bbf\u95ee<\/li>\n<\/ol>\n<p>\u73b0\u5728\uff0c\u6211\u4eec\u6765\u770b\u4e00\u4e2a\u66f4\u590d\u6742\u7684\u793a\u4f8b\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2023\/10\/more_complex_sample.png\" alt=\"\u5e26\u6709\u63a7\u5236\u56fe\u7684\u66f4\u590d\u6742\u793a\u4f8b\" width=\"472\" \/><\/p>\n<p>\u8fd9\u91cc\uff0c\u6211\u4eec\u6709\u4e24\u4e2a <code>if<\/code> \u5757\uff0c\u7b2c\u4e00\u4e2a\u5757\u7684\u6267\u884c\u65b9\u5f0f\u4f1a\u5f71\u54cd\u7b2c\u4e8c\u4e2a\u5757\u7684\u529f\u80fd\u3002 \u4e3a\u4e86\u652f\u6301\u8fd9\u79cd\u8bc4\u4f30\uff0cCLion \u5c06 <code>if<\/code> \u8bed\u53e5\u7684 exit \u8bed\u53e5\u62c6\u5206\u4e3a\u4e24\u4e2a\u4e0d\u540c\u7684\u4e0a\u4e0b\u6587\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2023\/10\/context_split.png\" alt=\"\u62c6\u5206\u4e0a\u4e0b\u6587\" width=\"508\" \/><\/p>\n<p>\u63a7\u5236\u6d41\u56fe\u7684\u540e\u7eed\u8282\u70b9\u91cd\u590d\u3002 \u5b83\u4eec\u51fa\u73b0\u4e24\u6b21\uff0c\u7b2c\u4e00\u6b21\u7528\u4e8e <code>if<\/code> \u8bed\u53e5\u7684 <code>Then<\/code> \u5206\u652f\uff0c\u7b2c\u4e8c\u6b21\u7528\u4e8e <code>Else<\/code> \u5206\u652f\u3002 \u5728\u7b2c\u4e00\u4e2a\u201c\u514b\u9686\u201d\u53d8\u91cf\u4e2d\uff0c<code>x<\/code> \u4fdd\u5b58\u503c <strong>1<\/strong>\uff08\u56e0\u4e3a\u5b83\u5bf9\u5e94\u4e8e <code>if<\/code> \u8bed\u53e5\u7684\u6b63\u5206\u652f\uff09\uff0c<code>y<\/code> \u4fdd\u5b58\u503c <strong>2<\/strong>\uff08\u5b83\u5b58\u50a8\u5728\u8282\u70b9 2 \u4e2d\uff09\u3002 \u5728\u7b2c\u4e8c\u4e2a\u201c\u514b\u9686\u201d\u53d8\u91cf\u4e2d\uff0c<code>x ! = 1<\/code>\uff0c<code>y<\/code> \u4e3a <strong>3<\/strong>\u3002<\/p>\n<p>\u7b2c\u4e8c\u4e2a\u6761\u4ef6 <code>x == 1<\/code>\uff0c\u5bf9\u5e94\u4e8e\u4e24\u4e2a\u514b\u9686\u7684\u8282\u70b9 <strong>4<\/strong> \u548c <strong>5<\/strong>\u3002 \u5728\u8282\u70b9 <strong>4<\/strong> \u5904\uff0c\u6761\u4ef6\u59cb\u7ec8\u4fdd\u5b58 true\uff0c\u56e0\u4e3a <code>x == 1<\/code>\u3002 \u540c\u65f6\uff0c\u5728\u8282\u70b9 <strong>5<\/strong> \u5904\uff0c\u5b83\u59cb\u7ec8\u4e3a false\u3002 \u56e0\u6b64\uff0c\u8282\u70b9 <strong>8<\/strong> \u548c <strong>10<\/strong> \u6c38\u8fdc\u65e0\u6cd5\u8bbf\u95ee\uff0c\u6761\u4ef6 <code>y == 2<\/code> \u53ea\u6709\u4e00\u4e2a\u53ef\u8bbf\u95ee\u7684\u514b\u9686\u8282\u70b9\uff0c\u5373\u8282\u70b9 <strong>9<\/strong>\u3002 \u5728\u6b64\u8282\u70b9\u5904\uff0c<code>y ! = 2<\/code>\uff0c\u56e0\u6b64\uff0c\u6b64\u6761\u4ef6\u59cb\u7ec8\u4e3a false\u3002<\/p>\n<h2 id=\"data_flow_analysis_in_action\">\u6570\u636e\u6d41\u5206\u6790\u7684\u5b9e\u9645\u8fd0\u4f5c\u60c5\u51b5<\/h2>\n<p>\u6211\u4eec\u6765\u770b\u770b\u8fd9\u4e9b\u6280\u672f\u5982\u4f55\u5e2e\u52a9 CLion \u5728 C++ \u7a0b\u5e8f\u4e2d\u53d1\u73b0\u7ec6\u5fae\u7684 bug\uff01 \u6211\u4eec\u51b3\u5b9a\u5206\u6790 <a href=\"https:\/\/github.com\/Z3Prover\/z3\" target=\"_blank\" rel=\"noopener\">Z3 \u5b9a\u7406\u8bc1\u660e\u5668<\/a>\uff0c\u4ee5\u4e0b\u662f\u6211\u4eec\u5728 CLion \u4e2d\u7684\u6570\u636e\u6d41\u5206\u6790\u7ed3\u679c\u3002<\/p>\n<p>\u8fd9\u91cc\uff0c\u53d8\u91cf <code>u<\/code> \u88ab\u521d\u59cb\u5316\u4e3a <code>null_lpvar<\/code>\uff0c\u7136\u540e\u53ef\u80fd\u88ab\u91cd\u65b0\u6307\u5b9a\u81f3\u76f8\u540c\u7684\u503c\uff08\u56e0\u4e3a <code>if<\/code> \u6761\u4ef6\u4e2d\u7684 <code>j == null_lpvar<\/code>\uff09\u3002 \u56e0\u6b64\uff0c\u6761\u4ef6 <code>u == null_lpvar<\/code> \u59cb\u7ec8\u4e3a <code>true<\/code>\u3002 \u7531\u4e8e\u8fd9\u6761 <code>if<\/code> \u5b50\u53e5\u7684 <code>true<\/code> \u5206\u652f\u4e2d\u6709\u8fd4\u56de\uff0c\u6240\u6709\u540e\u7eed\u4ee3\u7801\u90fd\u88ab\u6807\u8bb0\u4e3a\u65e0\u6cd5\u8bbf\u95ee\uff08\u62a5\u544a\u4e3a <a href=\"https:\/\/github.com\/Z3Prover\/z3\/issues\/6951\" target=\"_blank\" rel=\"noopener\">#6951<\/a>\uff09\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2023\/11\/z3_6951.png\" alt=\"\u95ee\u9898 6951\" width=\"690\" \/><\/p>\n<p>\u4e0b\u9762\u662f\u53e6\u4e00\u4e2a\u793a\u4f8b\u3002 \u8fd9\u91cc\uff0c\u65e0\u7b26\u53f7\u53d8\u91cf <code>i<\/code> \u59cb\u7ec8\u7b49\u4e8e\u6216\u5927\u4e8e\u96f6\uff0c\u5e76\u4e14\u5728 <code>else<\/code> \u5206\u652f\u4e2d\uff0c\u5b83\u4e0d\u4e3a\u96f6\u3002 \u56e0\u6b64\uff0c<code>i &gt; 0<\/code> \u6761\u4ef6\u59cb\u7ec8\u4e3a true\uff08\u62a5\u544a\u4e3a <a href=\"https:\/\/github.com\/Z3Prover\/z3\/issues\/6952\" target=\"_blank\" rel=\"noopener\">#6952<\/a>\uff09\uff1a<\/p>\n<p><img decoding=\"async\" src=\"https:\/\/blog.jetbrains.com\/wp-content\/uploads\/2023\/11\/z3_6952.png\" alt=\"\u95ee\u9898 6952\" width=\"700\" \/><\/p>\n<p>\u5728\u8fd9\u7bc7\u535a\u6587\u4e2d\uff0c\u6211\u4eec\u4ecb\u7ecd\u4e86\u6211\u4eec\u7684\u4e00\u9879\u6570\u636e\u6d41\u68c0\u67e5 \u2013 \u5e38\u91cf\u6761\u4ef6\u3002 CLion \u8fd8\u63d0\u4f9b\u4e86\u8bb8\u591a\u5176\u4ed6\u6570\u636e\u6d41\u68c0\u67e5\uff0c\u6211\u4eec\u5c06\u5728\u63a5\u4e0b\u6765\u7684\u535a\u6587\u4e2d\u4ecb\u7ecd\u5176\u4e2d\u4e00\u4e9b\u3002<\/p>\n<p align=\"center\"><a class=\"jb-download-button\" href=\"https:\/\/www.jetbrains.com.cn\/clion\/nextversion\" target=\"_blank\" rel=\"noopener\"><i class=\"download-icon\"><\/i>\u7acb\u5373\u8bd5\u7528<\/a><\/p>\n<p>\u60a8\u8ba4\u4e3a\u4ee3\u7801\u5206\u6790\u5728\u54ea\u4e9b\u60c5\u51b5\u4e0b\u6709\u7528\uff1f \u8bf7\u5728\u4e0b\u9762\u7684\u8bc4\u8bba\u4e2d\u4e0e\u6211\u4eec\u5206\u4eab\u60a8\u7684\u4f8b\u5b50\uff01<\/p>\n<\/p>\n<p>\u672c\u535a\u6587\u82f1\u6587\u539f\u4f5c\u8005\uff1a<\/p>\n\n    <div class=\"about-author \">\n        <div class=\"about-author__box\">\n            <div class=\"row\">\n                <div class=\"about-author__box-img\">\n                    <img decoding=\"async\" src=\"https:\/\/secure.gravatar.com\/avatar\/?s=200&#038;r=g\" width=\"200\" height=\"200\" alt=\"\" loading=\"lazy\"  class=\"avatar avatar-200 wp-user-avatar wp-user-avatar-200 photo avatar-default\">\n                <\/div>\n                <div class=\"about-author__box-text\">\n                                                        <\/div>\n            <\/div>\n        <\/div>\n    <\/div>\n","protected":false},"author":1297,"featured_media":401894,"comment_status":"closed","ping_status":"closed","template":"","categories":[601],"tags":[991,3369,2615],"cross-post-tag":[],"acf":[],"_links":{"self":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/clion\/420416"}],"collection":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/clion"}],"about":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/types\/clion"}],"author":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/users\/1297"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/comments?post=420416"}],"version-history":[{"count":6,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/clion\/420416\/revisions"}],"predecessor-version":[{"id":422028,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/clion\/420416\/revisions\/422028"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/media\/401894"}],"wp:attachment":[{"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/media?parent=420416"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/categories?post=420416"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/tags?post=420416"},{"taxonomy":"cross-post-tag","embeddable":true,"href":"https:\/\/blog.jetbrains.com\/zh-hans\/wp-json\/wp\/v2\/cross-post-tag?post=420416"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}