It sounds like you're encountering some compilation errors while trying to build your C++ project with Clang on Linux. Don't worry; these issues are common, especially when transitioning between different compilers and platforms. <br/> <br/> The errors you're seeing, like 'use of undeclared identifier', typically occur when certain functions or identifiers are not recognized by the compiler. In your case, functions like mbstowcs_s, wcstombs_s, and gmtime_s are specific to MSVC and might not be available in the Clang environment. <br/> <br/> For gmtime_s, you mentioned it's available from C11 onwards. However, for Linux environments, you should use gmtime_r instead, which is POSIX-compliant and widely supported. <br/> <br/> To fix these issues, you'll need to refactor your code to use platform-independent functions or find equivalents that are supported across different compilers and platforms. <br/> <br/> Regarding your CMakeLists.txt, ensure that you're correctly setting up compiler flags and including the necessary libraries for Clang on Linux. <br/> <br/> For more specific guidance on resolving these compilation errors, I'd recommend consulting forums like Stack Overflow or reaching out to developer communities focused on C++ and Linux development. <br/> <br/> And here's a resource you might find helpful for setting up Clang with CMake on Linux: <br/> <a href="https://mytechioo.com/best-linux-distro-for-programming/" rel="nofollow">Linux distros for Programmers</a> <br/> <br/> Stay persistent, and happy coding!