if-constexpr，编译报错expected a “(“

我的情况：vs 2017, nvcc, c++ 17, cuda c/c++ 混合编程

从在网上搜索到的结果看来是编译器的编译问题。

C++17 constexpr-if compiles but is highlighted as an error - Developer Community
g++ - C++17 refuses to compile example if constexpr giving expected ‘(’ before ‘constexpr’ - Stack Overflow

结论：属性页中，C/C++的c++语言标准要设置为ISO C++17标准，此外，cuda c/c++也要设置使用c++17编译。CUDA C/C++ -> Command line -> 其它选项，添加一行 -std=c++17 -Xcompiler "/std:c++17" 

c++ - How to enable C++17 code generation in VS2019 CUDA project - Stack Overflow
 

2025.7.13