qt - How to create layered project structure in c++ using qmake -

under windows using mingw, c++11, qt 5 , qmake have following project structure:

/my-project    my-project.pro    /my-app       my-app.pro       main.cpp    /module-a       module-a.pro       modulea.h       modulea.cpp    /module-b       module-b.pro       moduleb.h       moduleb.cpp 

the dependencies between modules should this:

my-app ==> module-a ==> module-b 

what want achieve my-app uses module-a, module-a uses module-b , my-app doesn't know module-b. module-a references module-b through implementation (the #include module-b located in .cpp of module-a).

i've tried implement configuring module-a , module-b static libraries in qmake. unfortunately while compiling receive linker error saying 'undefined reference moduleb::dosmthb()'

i understand reason of linking problem, question if somehow possible achieve similar proposed layered structure?

sources:

my-project.pro:

template = subdirs subdirs += module-b subdirs += module-a subdirs += my-app my-app.depends = module-a module-a.depends = module-b 

my-app.pro:

qt += widgets target = my-app template = app config += c++11 sources += *.cpp win32 {     includepath += $$clean_path($$pwd/../module-a)     dependpath += $$clean_path($$pwd/../module-a)     libs += $$clean_path($$out_pwd/../module-a/debug/libmodule-a.a)     pre_targetdeps += $$clean_path($$out_pwd/../module-a/debug/libmodule-a.a) } 

main.cpp:

#include <qapplication> #include <qgraphicsview> #include <qgraphicsscene>  #include "modulea.h"  int main(int argc, char *args[]) {     qapplication app(argc, args);     qgraphicsview view;     qgraphicsscene *scene = new qgraphicsscene(0, 0, 300, 300, &view);     modulea modulea;     scene->addtext(qstring::number(modulea.dosmtha())); // undefined reference moduleb::dosmthb()     view.setscene(scene);     view.show();     return app.exec(); } 

module-a.pro:

qt -= core gui target = module-a template = lib config += staticlib config += c++11 headers += *.h sources += *.cpp win32 {     includepath += $$clean_path($$pwd/../module-b)     dependpath += $$clean_path($$pwd/../module-b)     libs += $$clean_path($$out_pwd/../module-b/debug/libmodule-b.a)     pre_targetdeps += $$clean_path($$out_pwd/../module-b/debug/libmodule-b.a) } 

modulea.h:

#ifndef modulea_h #define modulea_h  struct modulea {     int dosmtha(); };  #endif // modulea_h 

modulea.cpp:

#include "modulea.h" #include "moduleb.h"  int modulea::dosmtha() {     moduleb other;     return other.dosmthb(); } 

module-b.pro:

qt -= core gui target = module-b template = lib config += staticlib config += c++11 headers += *.h sources += *.cpp 

moduleb.h:

#ifndef moduleb_h #define moduleb_h  struct moduleb {     int dosmthb(); };  #endif // moduleb_h 

moduleb.cpp:

#include "moduleb.h"  int moduleb::dosmthb() {     return 12345; } 

to fix example following changes required:

1) add config += create_prl .pro files of app's direct dependencies (in case module-a). won't hurt modify modules this.

explanation here: http://doc.qt.io/qt-5/qmake-advanced-usage.html#library-dependencies

2) in main .pro (in example my-project.pro) subdir declaration of app (subdirs += my-app) has placed after direct dependencies of app (after subdirs += module-a).

a hint second point i've found here: https://stackoverflow.com/a/1417859/6223445

3) libs property have defined using -l , -l options (at least under windows), e.g. instead of:

libs += $$clean_path($$out_pwd/../module-a/debug/libmodule-a.a) 

use following:

libs += -l$$clean_path($$out_pwd/../module-a/debug/) -lmodule-a 

the fixed solution looks (modified files only):

my-project.pro:

template = subdirs subdirs += module-b subdirs += module-a subdirs += my-app my-app.depends = module-a module-a.depends = module-b 

my-app.pro:

qt += widgets target = my-app template = app config += c++11 sources += *.cpp win32 {     includepath += $$clean_path($$pwd/../module-a)     dependpath += $$clean_path($$pwd/../module-a)     libs += -l$$clean_path($$out_pwd/../module-a/debug/) -lmodule-a     pre_targetdeps += $$clean_path($$out_pwd/../module-a/debug/libmodule-a.a) } 

module-a.pro:

qt -= core gui target = module-a template = lib config += staticlib config += c++11 config += create_prl headers += *.h sources += *.cpp win32 {     includepath += $$clean_path($$pwd/../module-b)     dependpath += $$clean_path($$pwd/../module-b)     libs += -l$$clean_path($$out_pwd/../module-b/debug/) -lmodule-b     pre_targetdeps += $$clean_path($$out_pwd/../module-b/debug/libmodule-b.a) }