[clang] --system-header-prefix flag

Controlling Diagnostics in System Headers

Assign --system-header-prefix flag to indicate what are system headers, thus the warnings

emit from those headers are ignored.

Its main purpose is to instruct the compiler to treat header files located in directories matching a specified prefix as "system headers."

Key Functionality

When a header file is designated as a system header, compilers like Clang typically suppress warnings that originate from within that header. This behavior is desirable because:

• Third-Party Libraries: Developers often use external libraries with their own header files. These headers might generate warnings with the project's specific compiler settings, but the project developer cannot or should not modify these library headers.
• Standard Library and OS Headers: Headers from the C++ Standard Library, C Standard Library, or the operating system itself are inherently system-level. Warnings from these are generally not actionable by the application developer.
• Reduced Noise: Suppressing these warnings allows developers to focus on issues within their own codebase.

#pragma clang enable-system-header-diagnostics