{"id":359,"date":"2020-04-02T09:07:36","date_gmt":"2020-04-02T01:07:36","guid":{"rendered":"https:\/\/www.notown.club\/?p=359"},"modified":"2020-04-05T22:55:32","modified_gmt":"2020-04-05T14:55:32","slug":"c%e8%a1%a8%e8%be%be%e5%bc%8f","status":"publish","type":"post","link":"https:\/\/www.notown.top\/?p=359","title":{"rendered":"C++\u8868\u8fbe\u5f0f"},"content":{"rendered":"\n

\u4e00\u3001\u5de6\u503c\u548c\u53f3\u503c<\/strong><\/p>\n\n\n\n

\u5728c\u91cc\uff0c\u5de6\u503c\u548c\u53f3\u503c\u6839\u672c\u533a\u522b\u5c31\u5728\u4e8e\uff0c\u5de6\u503c\u662f\u53ef\u4ee5\u88ab\u8d4b\u503c\u7684\uff0c\u800c\u53f3\u503c\u4e0d\u80fd\u3002
\u5728c++\u91cc\u5c31\u5927\u6709\u6587\u7ae0\u4e86\uff0c\u6700\u57fa\u672c\u7684\u533a\u522b\u5728\u4e8e\uff0c\u5de6\u503c\u5e94\u8be5\u662f\u6709\u5730\u5740\u7684\uff0c\u5b58\u50a8\u5728\u5185\u5b58\u4e2d\u7684\u67d0\u4e2a\u786e\u5b9a\u4f4d\u7f6e\u7684\uff0c\u800c\u53f3\u503c\u5e76\u4e0d\u5728\u5185\u5b58\u4e2d\u5360\u6709\u786e\u5b9a\u4f4d\u7f6e\u7684\u8868\u8fbe\u5f0f\u3002
\u5177\u4f53\u53ef\u53c2\u89c1\uff08https:\/\/blog.csdn.net\/xuwqiang1994\/article\/details\/79924310<\/a>\uff09
\uff08\u4f46\u6211\u4e2a\u4eba\u5bf9\u91cc\u9762\u8bb2\u7684\u8fd8\u4e0d\u662f\u5f88\u7406\u89e3\uff0c\u5148\u7801\u4f4f\uff0c\u4ee5\u540e\u518d\u56de\u6765\u770b\uff09<\/p>\n\n\n\n

\u4e8c\u3001sizeof\u8fd0\u7b97\u7b26<\/strong><\/p>\n\n\n\n

sizeof\u8fd0\u7b97\u7b26\u8fd4\u56de\u4e00\u6761\u8868\u8fbe\u5f0f\u6216\u4e00\u4e2a\u7c7b\u578b\u540d\u5b57\u6240\u5360\u7684\u5b57\u8282\u6570\u3002<\/p>\n\n\n\n

sizeof(\u7c7b\u578b\u540d\u5b57)
sizeof \u8868\u8fbe\u5f0f<\/code><\/p>\n\n\n\n

\u5bf9\u6570\u7ec4\u6267\u884csizeof\u8fd0\u7b97\u5f97\u5230\u6574\u4e2a\u6570\u7ec4\u6240\u5360\u7a7a\u95f4\u7684\u5927\u5c0f\uff0c\u7b49\u4ef7\u4e8e\u5bf9\u6570\u7ec4\u4e2d\u6240\u6709\u7684\u5143\u7d20\u5404\u6267\u884c\u4e00\u6b21sizeof\uff0c\u518d\u5c06\u7ed3\u679c\u6c42\u548c\u3002\uff08\u5373\u5bf9\u6570\u7ec4\u8fdb\u884csizeof\uff0c\u5e76\u4e0d\u4f1a\u88ab\u5f53\u6210\u662f\u6307\u9488\u5904\u7406\uff09
\u5bf9string\u5bf9\u8c61\u6216vector\u5bf9\u8c61\u6267\u884csizeof\u8fd0\u7b97\u53ea\u8fd4\u56de\u8be5\u7c7b\u578b\u56fa\u5b9a\u90e8\u5206\u7684\u5927\u5c0f\uff0c\u4e0d\u4f1a\u8ba1\u7b97\u8be5\u5143\u7d20\u5360\u7528\u4e86\u591a\u5c11\u7a7a\u95f4<\/p>\n\n\n\n

char ia[5];
constexpr size_t sz=sizeof(ia)\/sizeof(*ia);\/\/\u4e00\u79cd\u53ef\u4ee5\u6c42\u5f97\u6570\u7ec4\u5143\u7d20\u6570\u91cf\u7684\u65b9\u6cd5\u3002
int arr[sz];\/\/\u6b63\u786e<\/code><\/p>\n\n\n\n

\u4e09\u3001\u4e00\u4e9b\u9690\u5f0f\u7c7b\u578b\u8f6c\u6362<\/strong><\/p>\n\n\n\n

\u2460\u6570\u7ec4\u8f6c\u6362\u6210\u6307\u9488\uff1a\u5728\u5f88\u591a\u7528\u5230\u6570\u7ec4\u7684\u8868\u8fbe\u5f0f\u4e2d\uff0c\u6570\u7ec4\u4f1a\u88ab\u5f53\u6210\u662f\u6307\u9488\u5904\u7406\uff0c\u4f46\u5f53\u6570\u7ec4\u88ab\u7528\u4f5cdecltype\u5173\u952e\u5b57\u7684\u53c2\u6570\uff0c\u6216\u8005\u4f5c\u4e3a\u53d6\u5730\u5740\u7b26&\uff0csizeof\u53catypeid\u7b49\u8fd0\u7b97\u7b26\u7684\u8fd0\u7b97\u5bf9\u8c61\u65f6\uff0c\u6216\u7528\u4e00\u4e2a\u5f15\u7528\u521d\u59cb\u5316\u6570\u7ec4\u65f6\uff0c\u5219\u6570\u7ec4\u8fd8\u662f\u6570\u7ec4\u3002
\u2461\u5728\u6761\u4ef6\u8bed\u53e5\u7684\u62ec\u53f7\u91cc\uff0c\u7b97\u672f\u7c7b\u578b\u6216\u6307\u9488\u7c7b\u578b\u56de\u5411\u5e03\u5c14\u7c7b\u578b\u81ea\u52a8\u8f6c\u6362\u3002while(cin>>s)\/\/\u8fd9\u91cc\u5b9e\u9645\u68c0\u67e5\u7684\u662fistream\u7c7b\u578b\u7684\u503c\uff0cIO\u5e93\u91cc\u5b9a\u4e49\u4e86\u4eceistream\u5411\u5e03\u5c14\u503c\u8f6c\u6362\u7684\u89c4\u5219\uff0c\u82e5\u8bfb\u5165\u6210\u529f\u4e3atrue\uff0c\u53cd\u4e4bfalse<\/p>\n\n\n\n

\u56db\u3001\u663e\u5f0f\u8f6c\u6362<\/strong><\/p>\n\n\n\n

1\u3001\u547d\u540d\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362<\/p>\n\n\n\n

\u5f62\u5f0f\uff1a
cast-name<type>(expression);<\/code><\/p>\n\n\n\n

type\u662f\u8f6c\u6362\u7684\u76ee\u6807\u7c7b\u578b\uff0c\u800cexpression\u662f\u8981\u8f6c\u6362\u7684\u503c\uff0c\u5982\u679ctype\u662f\u5f15\u7528\u7c7b\u578b\uff0c\u5219\u7ed3\u679c\u662f\u5de6\u503c\u3002\u800ccast-name\u662fstatic_cast, dynamic_cast, const_cast, reinterpret_cast\u4e2d\u7684\u4e00\u79cd.<\/p>\n\n\n\n

static_cast<\/strong>, \u4efb\u4f55\u5177\u6709\u660e\u786e\u5b9a\u4e49\u7684\u7c7b\u578b\u8f6c\u6362\uff0c\u53ea\u8981\u4e0d\u5305\u542b\u5e95\u5c42const\uff0c\u90fd\u53ef\u4ee5\u4f7f\u7528static_cast\u3002<\/p>\n\n\n\n

int i=5,j=6;
double slope =static_cast<double>(j)\/i;<\/code>
static_cast\u5bf9\u4e8e\u7f16\u8bd1\u5668\u65e0\u6cd5\u81ea\u52a8\u6267\u884c\u7684\u7c7b\u578b\u8f6c\u6362\u975e\u5e38\u6709\u7528\u3002\u4f8b\u5982\uff0c\u53ef\u4ee5\u7528static_cast\u627e\u56de\u5b58\u5728\u4e8evoid*\u6307\u9488\u3002
void *p=&d;\/\/ \u4efb\u4f55\u975e\u5e38\u91cf\u5bf9\u8c61\u7684\u5730\u5740\u90fd\u80fd\u5b58\u5165void*
double dp = static_cast<double *>(p);\/\/\u5c06void * \u8f6c\u6362\u56de\u521d\u59cb\u7684\u6307\u9488\u7c7b\u578b\uff08\u524d\u63d0\uff1a\u6307\u9488\u539f\u5148\u6240\u6307\u7684\u7c7b\u578b\u5fc5\u987b\u5c31\u662fdouble\uff09<\/code><\/p>\n\n\n\n

const_cast<\/strong>, \u53ea\u80fd\u6539\u53d8\u8fd0\u7b97\u5bf9\u8c61\u7684\u5e95\u5c42<\/strong>const\uff0c\u53ef\u4ee5\u53bb\u6389\u8fd0\u7b97\u5bf9\u8c61\u7684\u5e95\u5c42const<\/p>\n\n\n\n

const char*pc;
char *p =const_cast<char *>(pc)\/\/\u6b63\u786e\uff0c\u4f46pc\u5e76\u672a\u6307\u5411\u5bf9\u8c61\uff0c\u6240\u6709\u901a\u8fc7p\u5199\u503c\u662f\u672a\u5b9a\u4e49\u884c\u4e3a\uff0c\u89e3\u5f15\u7528p\u53bb\u8d4b\u503c\u4f1aerror\u3002<\/p>\n\n\n\n

\u4e00\u4e9b\u4f8b\u5b50\uff1a
const char *cp;
char *q= static_cast<char *>(cp);\/\/\u9519\u8bef\uff0cstatic_cast\u4e0d\u80fd\u6539\u53d8const\u6027\u8d28
static_cast<string>(cp);\/\/\u6b63\u786e\uff0c\u5c06\u5b57\u7b26\u4e32\u5b57\u9762\u503c\u8f6c\u6362\u6210string\u7c7b\u578b
const_cast<string>(cp);\/\/\u9519\u8bef\uff0cconst_cast\u53ea\u6539\u53d8\u5e38\u91cf\u5c5e\u6027<\/code><\/p>\n\n\n\n

reinterpret_cast<\/strong>, \u901a\u5e38\u4e3a\u8fd0\u7b97\u5bf9\u8c61\u7684\u4f4d\u6a21\u5f0f\u63d0\u4f9b\u8f83\u4f4e\u5c42\u6b21\u4e0a\u7684\u91cd\u65b0\u89e3\u91ca\u3002\u672c\u8d28\u4e0a\u4f9d\u8d56\u673a\u5668\uff0c\u8981\u60f3\u5b89\u5168\u4f7f\u7528\uff0c\u5fc5\u987b\u5bf9\u6d89\u53ca\u7684\u7c7b\u578b\u548c\u7f16\u8bd1\u5668\u5b9e\u73b0\u8f6c\u6362\u7684\u8fc7\u7a0b\u90fd\u975e\u5e38\u4e86\u89e3\uff0c\u8fd9\u91cc\u5148\u4e0d\u638c\u63e1\u3002<\/p>\n\n\n\n

2\u3001\u65e7\u5f0f\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362 <\/strong><\/p>\n\n\n\n

type (expr) \/\/\u51fd\u6570\u5f62\u5f0f\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362
(type) expr \/\/c\u8bed\u8a00\u98ce\u683c\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362<\/code><\/p>\n\n\n\n

\u6839\u636e\u6240\u6d89\u53ca\u7684\u7c7b\u578b\u4e0d\u540c\uff0c\u65e7\u5f0f\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u5206\u522b\u5177\u6709\u4e0econst_cast, static_cast\u6216reinterpret_cast\u76f8\u4f3c\u7684\u884c\u4e3a\u3002\u5f53\u6211\u4eec\u5728\u67d0\u5904\u6267\u884c\u65e7\u5f0f\u7684\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u65f6\uff0c\u5982\u679c\u6362\u6210const_cast, static_cast\u4e5f\u5408\u6cd5\uff0c\u5219\u5176\u884c\u4e3a\u4e0e\u5bf9\u5e94\u7684\u547d\u540d\u8f6c\u6362\u4e00\u81f4\uff0c\u82e5\u4e0d\u5408\u6cd5\uff0c\u5219\u5176\u5b9e\u73b0\u7684\u529f\u80fd\u76f8\u7b49\u4e8ereinterpret_cast\u3002<\/p>\n\n\n\n

\u6362\u800c\u8a00\u4e4b\uff0c\u5728C++\uff0c\u8fd9\u4e9b\u5f3a\u5236\u7c7b\u578b\u8f6c\u6362\u66f4\u52a0\u660e\u786e\u4e86\uff0c\u662f\u6709\u5229\u4e8e\u6211\u4eec\u53bb\u5b9e\u9645\u8c03\u8bd5\uff0c\u6392\u9519\u3001\u4f7f\u7528\u7684\u3002<\/p>\n\n\n\n

\u518d\u63d2\u4e00\u70b9try\u8bed\u53e5\u90e8\u5206\u7684\u5185\u5bb9\uff1a<\/strong><\/p>\n\n\n\n

try{
\u00a0\u00a0\u00a0\u00a0program-statements
\u00a0\u00a0\u00a0\u00a0}catch (exeception-declaration) {
\u00a0\u00a0\u00a0\u00a0handelr-statements
   \u00a0\u00a0\u00a0\u00a0}catch (exeception-declaration) {
\u00a0\u00a0\u00a0\u00a0 \u2026
\u00a0\u00a0\u00a0\u00a0}<\/code><\/pre>\n\n\n\n
\u5176\u4e2dprogram-statements\u662f\u53ef\u80fd\u4f1a\u51fa\u73b0error\u7684\u8bed\u53e5
exeception-declaration\u662f\u9519\u8bef\u7684\u7c7b\u578b
handelr-statements\u662f\u51fa\u73b0\u8fd9\u79cd\u9519\u8bef\u540e\uff0c\u600e\u4e48\u5904\u7406\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
\u4e00\u3001\u5de6\u503c\u548c\u53f3\u503c \u5728c\u91cc\uff0c\u5de6\u503c\u548c\u53f3\u503c\u6839\u672c\u533a\u522b\u5c31\u5728\u4e8e\uff0c\u5de6\u503c\u662f\u53ef\u4ee5\u88ab\u8d4b\u503c\u7684\uff0c\u800c\u53f3\u503c\u4e0d\u80fd\u3002\u5728c++\u91cc\u5c31\u5927\u6709\u6587\u7ae0\u4e86\uff0c\u6700\u57fa…Continue reading C++\u8868\u8fbe\u5f0f<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[11],"tags":[],"class_list":["post-359","post","type-post","status-publish","format-standard","hentry","category-c"],"_links":{"self":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts\/359","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=359"}],"version-history":[{"count":8,"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts\/359\/revisions"}],"predecessor-version":[{"id":428,"href":"https:\/\/www.notown.top\/index.php?rest_route=\/wp\/v2\/posts\/359\/revisions\/428"}],"wp:attachment":[{"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=359"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=359"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.notown.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=359"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}