Question

I’ve got a project which has two source folders (main and lib). It produces a shared library and an executable. It is currently built as so:

• copy all files from both folders into a new temp folder
• run lib_makefile
• run main_makefile
• copy binaries out
• delete temp folder

This struck me as being a weird way to do things, so I tried building each in-place by adding -I../main to lib_makefile (and vice-versa). Unfortunately, this doesn’t seem to work.

Illustrative example:
foo.cpp (in lib) includes bar.h (in main), which includes baz.h (back in lib).

When I try to compile the shared lib, it correctly locates bar.h in main/, but then bails out with “no such file or directory” claiming it cannot find baz.h, even though baz.h is in the same directory as lib_makefile!

All includes are in the format #include “xxx.h” (i.e no relative paths in the include statements).

Is there a way to get this to work? I feel like I must be missing something obvious..

(nb: I can’t modify the #includes because other people still build this the copy-everything-across way)

Answer 1

You should add something like -I../lib (or whatever your library path is) to the makefile for the library as well.

The reason for this is that the pre-processor looks for include-files relative to the directory the current file is in, not from where the original file is in.