namespace std:: does not contain optional

Question

i am doing the Vulkan Tutorial https://vulkan-tutorial.com/

#define GLFW_INCLUE_VULKAN
#include<GLFW/glfw3.h>
#include<optional>

struct s {
    std::optional<uint32_t> num;//Intellisense Error
};

int main() {
    return 5;
}

I started with an empty project and added includes and libraries; I can compile and run without including std::optional.

When i use std::optional I get c2039 "optional is not a member of std"

I am running Windows 10, and VisualStudio 2019

What is going on here ?

thx.

Are you compiling with C++17 support? This type was added in C++17. Many compilers still default to C++14. — cdhowie, Jun 14 '20 at 08:18
Which C++ Standard are you using? Because `std::optional` is a C++17 feature. Look at this thread [Change C++ Standard VS](https://stackoverflow.com/questions/41308933/how-to-enable-c17-compiling-in-visual-studio) — ElGusanito, Jun 14 '20 at 08:18

score 13 · Accepted Answer · edited Jun 20 '20 at 09:12

13

std::optional requires C++17.

Live on Godbolt.

you can use /std:c++17 flag on MSVC and -std=c++17 on gcc/clang.

edited Jun 20 '20 at 09:12

Community

1
1

answered Jun 14 '20 at 08:34

Oblivion

6,731
2
12
32

2

In Visual Studio need add flag `/std:c++17` to Debug -> Project Properties -> C/C++ -> All options -> Additional Options – Elmir Dec 04 '21 at 22:32

namespace std:: does not contain optional

1 Answers1