Missing header files for linked ".c" file - linker

Question

I have linked a ".c" file to another one. ld doesn't return any error but the compiler can't find included header files in this ".c" file and returns this error:
../libvmi/driver/xen.c:27:20: fatal error: libvmi.h: No such file or directory
Here is the Makefile of my project:
## Source directory
SUBDIRS =
INCLUDES = -I$(top_srcdir) $(top_srcdir)/libvmi
AM_LDFLAGS = -L$(top_srcdir)/libvmi/.libs/ $(top_srcdir)/libvmi/driver $(top_srcdir)/libvmi/libvmi.h
LDADD = -lvmi -lm $(LIBS) $(top_srcdir)/libvmi/driver/xen.c $(top_srcdir)/libvmi/libvmi.h
bin_PROGRAMS = module-list process-list map-symbol map-addr dump-memory
module_list_SOURCES = module-list.c
process_list_SOURCES = process-list.c
map_symbol_SOURCES = map-symbol.c
map_addr_SOURCES = map-addr.c
dump_memory_SOURCES = dump-memory.c
As you see above I thought I should add "$(top_srcdir)/libvmi" to "INCLUDES"; this is the directory that libvmi.h is located.
The original Makefile is:
## Source directory
SUBDIRS =
INCLUDES = -I$(top_srcdir)
AM_LDFLAGS = -L$(top_srcdir)/libvmi/.libs/
LDADD = -lvmi -lm $(LIBS)
c_sources = process-list.c $(top_srcdir)/libvmi/driver/xen.c
bin_PROGRAMS = module-list process-list map-symbol map-addr dump-memory
module_list_SOURCES = module-list.c
process_list_SOURCES = $(c_sources)
map_symbol_SOURCES = map-symbol.c
map_addr_SOURCES = map-addr.c
dump_memory_SOURCES = dump-memory.c
I have modified it to link "libvmi/driver/xen.c" to process-list.c file which are located in different directories.
This is because of something's wrong in Makefile, yes?

Answer 1

Add a -I to the path you added. Note this is a compiler, not linker question

Answer 2

The reason ld doesn't return an error is because it is not invoked. The error message you are getting is coming from the compiler, and the loader is not invoked until the compiler is successful.
Yes, you do need to add $(source_dir)/libvmi to INCLUDES; you just need to do it symmetrically with the existing entry:
INCLUDES = -I$(top_srcdir) -I$(top_srcdir)/libvmi
Note the -I preceding the directory name. You have a similar problem in AM_LDFLAGS and LDADD:
AM_LDFLAGS = -L$(top_srcdir)/libvmi/.libs/ -L$(top_srcdir)/libvmi/driver
LDADD = -lvmi -lm $(LIBS)
but you do not want to add the header file $(top_srcdir)/libvmi/libvmi.h to the load flags. Headers are not libraries; headers are not appropriate for sending to the linker/loader. You should only supply the linker/loader with object files, libraries, and options — no source files, no headers.
That more or less deals with the surface issues. What is the real problem you are trying to solve?
If you need to link with code from a library built in libvmi directory, why don't you make the dependency changes in this makefile to pick up the library from the libvmi directory (and separately run the build for the library in the libvmi directory)? Or, if you really want to do the compilation in the current directory (but why?), create links to the libvmi files locally (or copy them; no, on second thoughts, don't copy them), and compile them locally? Mixed directory working is painful at best — and to be avoided when possible, which it almost always is.
I note that the original makefile does in fact include -lvmi on the link line, so what I outlined is what you're expected to use. Why isn't that working for you? This is very much an XY Problem. I recommend reworking the question so that you get a solution to the real problem you started out with, rather than the artificial problem you ran into attempting to solve the real problem in a misguided way.