藉此标题延伸问一个问题~ http://stackoverflow.com/questions/11781724/do-i-really-have-to-worry-about-alignment-when-using-placement-new-operator 缩成 https://goo.gl/GYsFKF 也许是我阅读障碍 我试着理解他的英文但我看不太懂 一开始他贴 18.6.1.3 Placement forms [new.delete.placement] 说这函数被保留 <== 什麽函数 void* operator new(吃size跟void*) 吗? C++ program 不应该有函数取代这个 (但就我理解不是可以overload operator new?) The provisions of (3.7.4) include that the returned pointer should be suitably aligned, so it's fine for void* operator new (std::size_t size, void* ptr) noexcept to return a nonaligned pointer if one is passed in. This doesn't let you off the hook 这段整个看不懂, provisions of (3.7.4) 这是什麽? 然後他讲的听起来是 你overload後 return出一个ptr+1 byte 不aligned的也没关系. 然後第二块黄色的又看起来说assumed要aligned. 然後突然一个结论 So if you pass unaligned storage to a placement-new expression you're violating the assumption that the storage is aligned, and the result is UB. 说不能unaligned..... 完全无法理解整个解答 在这边请教一下各位 是不是只有我看不太懂, 还是我必须要有什麽background才能 谢谢˙ --

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