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--md

This option instructs the compiler to compile the source and write makefile dependency lines to a file.

The output file is suitable for use by a make utility.

The compiler names the file filename.d, where filename is the name of the source file. If you specify multiple source files, a dependency file is created for each source file.

If you want to produce makefile dependencies and preprocessor source file output in a single step, you can do so using the combination --md -E (or --md -P to suppress line number generation).