{"id":1953,"date":"2014-09-04T10:22:06","date_gmt":"2014-09-04T09:22:06","guid":{"rendered":"http:\/\/roboblog.fatal-fury.de\/?p=1953"},"modified":"2014-09-04T10:22:06","modified_gmt":"2014-09-04T09:22:06","slug":"virtual-inheritance-and-sizeof","status":"publish","type":"post","link":"http:\/\/roboblog.fatal-fury.de\/?p=1953","title":{"rendered":"virtual inheritance and sizeof()"},"content":{"rendered":"<p>Folgender Code:<\/p>\n<pre><code>\r\n#include < iostream >\r\n#include < stdint.h >\r\n\r\nusing namespace std;\r\n\r\nclass Base {\r\n   public:\r\n   int32_t a;\r\n};\r\n\r\nclass Derived :  public Base {\r\npublic:\r\n  int32_t b;\r\n};\r\n\r\nclass VirtualDerived : virtual  public Base {\r\npublic:\r\n  int32_t c;\r\n};\r\n\r\nint main() {\r\n  cout << \"sizeof Base \" << sizeof(Base) << \"\\n\";\r\n  cout << \"sizeof Derived \" << sizeof(Derived) << \"\\n\";\r\n  cout << \"sizeof VirtualDerived \" << sizeof(VirtualDerived) << \"\\n\";\r\n\r\n  return 0;\r\n}\r\n<\/code><\/pre>\n<p>ergibt auf einer 32Bit Maschine folgende Ausgabe<\/p>\n<pre>\r\nsizeof Base 4\r\nsizeof Derived 8\r\nsizeof VirtualDerived 12\r\n<\/pre>\n<p>Die Gr\u00f6\u00dfe der VirtualDerived Klasse ist also nicht einfach die Summer zweier 4Byte Variablen, sondern auch noch zus\u00e4tzlich ein 4Byte Pointer auf die Base Klasse.<\/p>\n<p>Auf einer 64Bit Maschine sind es entsprechend 16Byte<\/p>\n<pre>\r\nsizeof Base 4\r\nsizeof Derived 8\r\nsizeof VirtualDerived 16\r\n<\/pre>\n","protected":false},"excerpt":{"rendered":"<p>Folgender Code: #include < iostream > #include < stdint.h > using namespace std; class Base { public: int32_t a; }; class Derived : public Base { public: int32_t b; }; class VirtualDerived : virtual public Base { public: int32_t c; }; int main() { cout<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[14,17],"class_list":["post-1953","post","type-post","status-publish","format-standard","hentry","category-allgemein","tag-c","tag-cpp"],"_links":{"self":[{"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=\/wp\/v2\/posts\/1953","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=1953"}],"version-history":[{"count":5,"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=\/wp\/v2\/posts\/1953\/revisions"}],"predecessor-version":[{"id":1958,"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=\/wp\/v2\/posts\/1953\/revisions\/1958"}],"wp:attachment":[{"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=1953"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=1953"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/roboblog.fatal-fury.de\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=1953"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}