The --pch command-line option enables automatic PCH file processing. This means that the compiler automatically looks for a qualifying PCH file, and reads it if found. Otherwise, the compiler creates one for use on a subsequent compilation.

When the compiler creates a PCH file, it takes the name of the primary source file and replaces the suffix with .pch. The PCH file is created in the directory of the primary source file unless the --pch_dir option is specified.