Using JSBSim with CPM.cmake or FetchContent

[0-Seby]

Hello, I am new to developing and would like to use JSBSim in a personal project. For that I would like to use the JSBSim c++ API, but I have been running into a few problems.

I managed to write a test program that reads a JSBSim script and runs it successfully, but I am building my program using g++ and specifiying the library file and the header folder manually each time I build it. However, I would like to use CMake with a package manager (like CPM) to manage my dependencies, and simplify the build process. Unfortunately, I do not completely understand what I am doing, so I am getting many linking errors, which I have not been able to solve through reading documentation and youtube tutorials.

My CMakeLists.txt looks like this:

cmake_minimum_required(VERSION 3.20)
set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

### Project Initialization
project(tvc VERSION 1.0)
add_executable(tvc test.cpp)

set(CMAKE_EXPORT_COMPILE_COMMANDS ON)

### Dependencies
include(FetchContent)
include(cmake/CPM.cmake)

CPMAddPackage(
  NAME jsbsim
  GITHUB_REPOSITORY JSBSim-Team/jsbsim
  GIT_TAG v1.2.2
  OPTIONS
  "BUILD_DOCS FALSE"
  "BUILD_PYTHON_MODULE FALSE"
  "BUILD_SHARED_LIBS TRUE"
  "JSBSIM_ENABLE_PLUGINS TRUE"
)

target_link_libraries(tvc jsbsim)

# Print Targets
get_property(allTargets DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR} PROPERTY BUILDSYSTEM_TARGETS)
message(STATUS "All targets: ${allTargets}")

My test.cpp looks like this:

#include "build/_deps/jsbsim-src/src/FGFDMExec.h"
#include <iostream>
#include <string>
#include <vector>

int main(int argc, char **argv) {

  SGPath scriptPath("/home/default/Documents/TVC/TVC_github/build/_deps/"
                    "jsbsim-src/scripts/737_cruise.xml");
  SGPath rootPath(
      "/home/default/Documents/TVC/TVC_github/build/_deps/jsbsim-src");

  JSBSim::FGFDMExec *FDMExec = new JSBSim::FGFDMExec();

  FDMExec->SetRootDir(rootPath);
  FDMExec->SetAircraftPath(SGPath("aircraft"));
  FDMExec->SetEnginePath(SGPath("engine"));
  FDMExec->SetSystemsPath(SGPath("systems"));

  std::cout << FDMExec->GetRootDir() << std::endl;

  FDMExec->LoadScript(
      scriptPath, 0.0,
      SGPath("/home/default/Documents/TVC/TVC_github/build/_deps/jsbsim-src/aircraft/737/cruise_init.xml"));

  std::cout << "Loading done" << std::endl;

  FDMExec->SetDebugLevel(1);

  FDMExec->RunIC();
  bool result = FDMExec->Run();
  while (result) {
    result = FDMExec->Run();
  }
}

The command i used to build my program successfully using g++ is:

g++ test.cpp -I/home/default/Documents/TVC/TVC_github/build/_deps/jsbsim-src/src -L/home/default/Documents/TVC/TVC_github/build/_deps/jsbsim-build -lJSBSim -o test

The error i get when building using cmake --build

[  1%] Building CXX object CMakeFiles/tvc.dir/test.cpp.o
In file included from /home/default/Documents/TVC/TVC_github/build/_deps/jsbsim-src/src/FGFDMExec.h:46,
                 from /home/default/Documents/TVC/TVC_github/test.cpp:1:
/home/default/Documents/TVC/TVC_github/build/_deps/jsbsim-src/src/models/FGPropagate.h:43:10: fatal error: models/FGModel.h: No such file or directory
   43 | #include "models/FGModel.h"
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
make[2]: *** [CMakeFiles/tvc.dir/build.make:76: CMakeFiles/tvc.dir/test.cpp.o] Error 1
make[1]: *** [CMakeFiles/Makefile2:474: CMakeFiles/tvc.dir/all] Error 2
make: *** [Makefile:156: all] Error 2

I would be very greatful if somebody could explain the errors I am getting, and how to fix them. If my approach is wrong, I would also appreciate some insight on how to do it correctly.

Thank you for your time,
Sebastian

[bcoconni]

Since the compiler cannot locate the headers, I'd say you need to add a target_include_directories to your CMake file:

target_include_directories(tvc PRIVATE path/to/jsbsim/headers)

[0-Seby]

Hello,

Thank you for answering. I added the target include directory and my cmake compilation seems to be working now. Thank you!