MSVC中调用constexpr std::max处理符号化constexpr初始化列表时编译失败问题

Understanding the Problem #

Your issue comes down to how MSVC 19.29 handles constexpr std::initializer_list variables when passed to standard library functions like std::max or std::max_element. While Clang and GCC correctly process these variables in a constexpr context, this specific MSVC version fails to resolve the overload or validate the usage properly.

Answers to Your Questions #

1. Fix Without Extra Macros or Duplication #

Absolutely, there are clean, maintainable ways to avoid repeating your initializer list values. Here are two reliable options:

Option 1: Use a Constexpr Array Instead of Initializer List

Swap the std::initializer_list variable for a constexpr array—arrays have more consistent constexpr support across compilers, and you can still convert it to an initializer_list for runtime calls:

#include <algorithm>
#include <initializer_list>
#define FOO_1 1
#define FOO_2 2
#define FOO_3 3

class Baz {
    static constexpr int data[] = {FOO_1, FOO_2, FOO_3};
    static constexpr auto data_max = *std::max_element(std::begin(data), std::end(data));
    void bar(std::initializer_list<int>);
    void test();
};

void Baz::test() {
    // Convert the array to initializer_list for the bar call
    bar({std::begin(data), std::end(data)});
}

This keeps your values centralized, eliminates duplication, and works seamlessly across MSVC, Clang, and GCC.

Option 2: Wrap the Initializer List in a Constexpr Lambda

If you want to stick with std::initializer_list, wrapping it in a constexpr lambda helps MSVC recognize the constexpr context correctly:

class Baz {
    static constexpr auto data = []{ return std::initializer_list<int>{FOO_1, FOO_2, FOO_3}; }();
    static constexpr auto data_max = std::max(data);
    void bar(std::initializer_list<int>);
    void test();
};

void Baz::test() {
    bar(data);
}

The lambda forces MSVC to evaluate the initializer list in a constexpr context upfront, making it compatible with std::max.

2. Is This a Known MSVC Bug? #

Yes, this is a known issue with MSVC 19.29 (included in Visual Studio 2019 version 16.10). The bug relates to how the compiler handles constexpr std::initializer_list variables when passed to standard library algorithms. It was fixed in later MSVC versions starting with 19.30 (corresponding to Visual Studio 2019 version 16.11 and newer).

You don’t need to submit a new bug report—this issue has already been addressed in subsequent updates. If upgrading your MSVC version is feasible, that would also resolve the problem without modifying your original code.

内容的提问来源于stack exchange，提问作者Marek R