why a derived class with virtual base classes can not have constexpr constructors?

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why a derived class with virtual base classes can not have constexpr constructors?

ma guangzhi 6

This question is about error E2403 generated by Visual stuidio 2019 C++.

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Answer 1

YujianYao-MSFT 4,296 Microsoft External Staff

Hi @ma guangzhi ,

I recommend that you read this documentation, which states:

It can't be virtual. A constructor can't be defined as constexpr when the enclosing class has any virtual base classes.

Best regards,

Elya

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ma guangzhi 6 Reputation points

2022-02-03T03:40:02.283+00:00

I have read it, but I want to know why.
YujianYao-MSFT 4,296 Reputation points Microsoft External Staff

2022-02-03T09:08:17.15+00:00

Hi @ma guangzhi ,

Have you tried setting the C++ Language Standard to C++20 or latest? If not, I suggest you try setting it up.
ma guangzhi 6 Reputation points

2022-02-03T14:51:08.947+00:00

I have read it, but I want to know why. I learn things not by just remembering.
Viorel 122.5K Reputation points

2022-02-04T20:46:03.85+00:00

In the past, virtual constexpr functions were prohibited. In case of virtual bases, the prohibition still exists. Maybe “the authors simply didn't feel like analyzing the consequences of changing it at this time” [https://lists.isocpp.org/std-proposals/2019/06/0084.php].

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why a derived class with virtual base classes can not have constexpr constructors?

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