How To Get g++ to list paths to all #included files

Question

I would like to have g++/gcc tell me the paths to everything non-system it is #include-ing in C++ build. Turns out, that is a tough search as Google mus-interprets it about ten

Answer 1

Try gcc or g++ with the -H option (to the preprocessor part of it). From the doc:

-H

Print the name of each header file used, in addition to other normal activities. Each name is indented to show how deep in the ‘#include’ stack it is. Precompiled header files are also printed, even if they are found to be invalid; an invalid precompiled header file is printed with ‘...x’ and a valid one with ‘...!’ .

It tells you all the headers which are included. You may filter out (with grep -v or awk) those that you don't want.

You could also consider developing your GCC plugin to register these headers somewhere (e.g. in your sqlite database), perhaps inspired by this draft report, or the CHARIOT or DECODER European projects. You could also consider using, or extending, the Clang static analyzer.

In contrast to the -M options suggested in Oliver Matthews' answer, it does not tell you more (but gives all the included files).

Answer 2

You need to invoke g++ with the -M option.

From the manual:

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.

It's worth reading the manual to consider the other -M sub options (-MM and -MF in particular may be of use).