sizeof emtpy c

raidtest

于 2023-12-14 17:16:25 发布

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文章标签： c++

本文链接：https://blog.youkuaiyun.com/raidtest/article/details/135000317

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文章讨论了在不同类层次结构中，当类A从B派生且C从A派生时，共享VPTR导致C的大小；反之，如果C从两个基类A和B派生，每个基类都有虚拟函数，则C将有两个VPTR，总大小是两个VPTR的和。

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In a class hierarchy where A is derived from B, and C is derived from A, all having virtual functions, A and C would share the same VPTR as they are in the same class hierarchy. Therefore, the size of C would be the size of a single VPTR, which is typically 8 bytes on a 64-bit platform.

On the other hand, when a class C is derived from two parent classes A and B, and both A and B have a virtual function, C would have two VPTRs - one for each class hierarchy. Therefore, the size of C would be the sum of the sizes of the VPTRs for A and B, which is typically 16 bytes on a 64-bit platform.