constexpr错误； VS2017 C ++编译器回归？ [英] constexpr errors; VS2017 C++ compiler regression?

问题描述

仅安装了VS2017，该版本自2015年以来声称具有更高的C ++ 14支持（基本）。
试一下我的一个使用 constexpr 的项目，并注意到其中似乎存在一些回归。

Just installed VS2017, which claims to have superior C++14 support since 2015 (which was rudimentary). Gave it a spin on one of my projects which uses constexpr, and noticed what appear to be some regressions.

此代码：

struct s
{
    size_t i;
    constexpr s(nullptr_t) noexcept : i(0) {}
};
static_assert(s(nullptr).i == 0, "!!");

在VS2015和Clang上没有问题，但是在VS2017中出现新错误：

Compiles no problem on VS2015 and Clang, but I get a new error in VS2017:

error C2131: expression did not evaluate to a constant
note: failure was caused by unevaluable pointer value
note: while evaluating 's::s(&s{(null)})'

这段代码看起来不错对？ constexpr 是否意味着 nullptr 有问题？

我很惊讶对此进行回归基本可能会出现，我怀疑我的代码肯定有问题...

This code looks fine right? Is constexpr meant to have a problem with nullptr?
I'm astonished a regression this basic could appear, I suspect there must be something wrong with my code...

推荐答案

constexpr构造函数（std :: nullptr_t）导致错误C2131：表达式未求值为常量

constexpr constructor(std::nullptr_t) causes "error C2131: expression did not evaluate to a constant"

此问题是已报告为Visual Studio 2017中的错误版本15.1。

还有另一个问题由OP（？）先前报告。

This issue was reported as a bug in Visual Studio 2017 version 15.1.
There was a variation of another issue reported earlier by the OP (?).

此问题已在以下版本中修复：Visual Studio 2017版本15.6预览版1

This was fixed in: Visual Studio 2017 version 15.6 Preview 1

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