Identify the Cause of the Error
- This error commonly occurs when the C++ version being used does not support the `std::is_same_v` feature. It was introduced in C++17 as a convenient variable template shorthand for `std::is_same::value`. If you see this error, it's likely that your project is being compiled with a C++ standard older than C++17.
- Ensure that the file where the error occurs actually includes the `` header, which is where `std::is_same` and `std::is_same_v` are defined.
Ensure the Correct C++ Standard Version
- Review your build system or compiler settings to check if the correct version of the C++ standard is specified. You will need at least C++17 to use `std::is_same_v`.
- For GCC or Clang, ensure you use the `-std=c++17` flag (or higher) during compilation. You might do this by adding the following to your compiler command line:
g++ -std=c++17 -o your_program your_program.cpp
- If you're using CMake, make sure your `CMakeLists.txt` specifies C++17 or higher:
set(CMAKE_CXX_STANDARD 17)
Replace with Compatible Code
- In scenarios where upgrading the C++ standard might not be feasible, you can define your own convenience variable template if your compiler supports variable templates but is set to a lower standard:
template <typename T, typename U>
constexpr bool is_same_v = std::is_same<T, U>::value;
- Alternatively, you can replace `std::is_same_v` with `std::is_same::value` in your code, which offers the same functionality but is more verbose.
Verify Toolchain and Dependencies
- Make sure the version of your compiler is sufficiently modern to support C++17. Usually, GCC 7, Clang 5, and MSVC++ 2017 (version 15.0) and onwards support C++17 features.
- If your project relies on third-party libraries or frameworks, ensure that they are compatible with the C++ version you intend to use.
Testing and Validation
- After making changes, build your project again to check whether the error persists. Confirm that no other parts of your code depend on C++ features unsupported by your current compiler or standard setting.
- Run unit tests and any integration tests available for your firmware to ensure that the changes rectify the issue without introducing new bugs.
