Include header file of external library in another header file - c

Question

Currently I have the following project structure, where the libs directory purpose is to store external C libraries that I download from github because they are not available on my OS's repos:
├── cli
│   └── cli.c
├── libs
│   ├── meson.build
│   └── pqueue
│   ├── pqueue.c
│   └── pqueue.h
├── modules
│   ├── algorithms
│   │   ├── a_star.c
│   │   └── a_star.h
│   ├── meson.build
├── meson.build
Where libs/meson.build is:
libpqueue_sources = [
'pqueue/pqueue.c',
]
pqueue_lib = shared_library('pqueue', libpqueue_sources)
pqueue_dep = declare_dependency(link_with: pqueue_lib)
modules/meson.build is:
algs_sources = [
'algorithms/a_star.c',
]
algs_lib = static_library('algorithms',
sources: algs_sources,
include_directories: libs_include_dirs,
dependencies: pqueue_dep)
and meson.build is:
project('graph-search', 'c')
graph_search_include_dirs = include_directories('modules')
libs_include_dirs = include_directories('libs')
subdir('libs')
subdir('modules')
cli_sources = [
'cli/cli.c'
]
executable('cli',
sources: cli_sources,
include_directories : graph_search_include_dirs,
link_with: [algs_lib])
My problem arises when I try to make an #include "pqueue/pqueue.h" inside a_star.h, it says /modules/algorithms/a_star.h:5:10: fatal error: pqueue/pqueue.h: No such file or directory, but when I move the include to a_star.c the error disappears. Sadly I need to include it on the header file because I need to export a struct that uses a type of pqueue.h
Is there a way to include pqueue.h inside a_star.h without using paths like ../../libs/pqueue/pqueue.h?

Answer 1

Because you don't specify libs_include_dirs for cli.c to build, compiler don't know how to search pqueue/pqueue.h.
Change your meson.build to include libs_include_dirs.
diff --git a/meson.build b/meson.build
index 4087a00..3347466 100644
--- a/meson.build
+++ b/meson.build
## -8,5 +8,5 ## cli_sources = [
]
executable('cli',
sources: cli_sources,
- include_directories : graph_search_include_dirs,
+ include_directories : [graph_search_include_dirs, libs_include_dirs],
link_with: [algs_lib])