Question

gcc -MD file.c creates a dependency output file named file.d. But I dont understand the need of creating this file ( dependency file ), because when error comes while compilation, no dependency file is generated. So can anyone throw some light when he/she has used this dependency file or some usefulness of this file / feature of gcc.

Answer 1

The file.d file can be understand by make. You often first generate the .d files, include them into your Makefile and then compile the c-files only if one of the included headers has changed.

Don’t bother about if you don’t use make.

GCC documentation says:

Instead of outputting the result of preprocessing, output a rule suitable for make describing the dependencies of the main source file. The preprocessor outputs one make rule containing the object file name for that source file, a colon, and the names of all the included files, including those coming from -include or -imacros command line options.