[SOLVED] How to remove [[nodiscard]] attribute from std::expected?

How to remove [[nodiscard]] attribute from std::expected?

In the recently released Visual Studio 2022 version 17.14, std::expected class template is marked with [[nodiscard]] attribute.

As a result the program as follows:

#include <expected>

std::expected<void,int> f() {
    return {};
}

int main() {
    f();
}

started showing the warning:

warning C4834: discarding return value of function with [[nodiscard]] attribute

I know that ignoring std::expected is not a good practice, but our codebase is large and it is hard to change all such places quickly.

I can silence the warning by writing (void)f() here. But again, it requires to change every such calling place, which can be too many.

Is there a way to remove [[nodiscard]] attribute from std::expected in Microsoft STL, but keep the attribute for other functions and classes in the standard library?

Solution

I think it is not good idea to ignoring but if you want to suppress the warning only for specific parts of the code, you can use preprocessor directives like this.


#pragma warning(push)
#pragma warning(disable: 4834)  // Disable specific warning for discarding [[nodiscard]]

f();  // No warning here

#pragma warning(pop)  // Restore the warning state