要触发nrvo， 返回值写在第一行， 然后return语句和返回值处于同一block.

如果代码有if动态分支，你在if里边返回的时候触发不了nrvo.

我感觉nrvo是一个编译期行为， 编译器如果无法预测你的分支，nrvo就不可能.


【 在 allegro (静水流深) 的大作中提到: 】
: I read again the NRVO carefully, seems I mis-understand the NRVO in case 5.
: NRVO needs to know which variable to return at construction.
: But still I have question for case-5, const effectively blocks the move ctor.
: ...................
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