[SOLVED] std::numbers has not been declared - GCC 11.2 on Windows

Issue

I have GCC 11.2.0 installed on my Windows 10 machine (from here: https://winlibs.com/). I have updated the environment variable Path to C:\MinGW\bin

gcc version 11.2.0 (MinGW-W64 x86_64-posix-seh, built by Brecht Sanders)

I'm using VSCode with the C/C++ extension configured to use the correct compiler path.

I want to use a C++20 feature which is std::numbers::sqrt2

Still I get an error telling me it doesn't know std::numbers

    [Running] cd "c:\Users\XX\XX\" && g++ 
    main.cpp -o main && "c:\Users\XX\XX\"main
    main.cpp: In function 'double sin_x_plus_cos_sqrt2_times_x(double)':
    main.cpp:15:41: error: 'std::numbers' has not been declared
    15 |     return std::sin(x) + std::cos( std::numbers::sqrt2 * x );
       | 

I've added the header #include <numbers>

What am I missing ?

Solution

Default version of c++ standard for this version of gcc is C++17. See this: https://godbolt.org/z/4Pjzd5r7s

Use

g++ main.cpp -o main -std=c++20

to force C++20

There is some support of C++20 in gcc, but it is simply to early to make it default standard.

Answered By - Marek R