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Qt and non-Qt nodes in the same package?

asked 2012-02-27 18:59:44 -0500

pmwalk gravatar image

updated 2014-01-28 17:11:27 -0500

ngrennan gravatar image

I have used qt_create to make a Qt ROS package. However, when I try to add another basic ROS node (one that doesn't use Qt), I get the following error, stating that I have duplicate main functions:

  make[3]: Entering directory `/home/phillip/ROS_workspace/ros-swarm-tools/interpreter/build'
  Linking CXX executable ../bin/interface
  CMakeFiles/interface.dir/src/interpreter.o: In function `main':
  /home/phillip/ROS_workspace/ros-swarm-tools/interpreter/src/interpreter.cpp:158: multiple definition of `main'
  CMakeFiles/interface.dir/src/main.o:/home/phillip/ROS_workspace/ros-swarm-tools/interpreter/src/main.cpp:20: first defined here
  collect2: ld returned 1 exit status

It seems as though cmake is trying to link the new ROS node (interpreter) with the old one (interface) in the ../bin/ folder. I am not familiar enough with cmake to know how to modify CMakeLists.txt to prevent it from doing this. Am I right in thinking that this is the problem? If so, how would I go about fixing it, or is there an easy tutorial somewhere for combining multiple nodes in a ROS Qt project?

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answered 2012-02-27 19:42:53 -0500

Daniel Stonier gravatar image

The qt_create script by default sets up a package for development of a single binary (keeps it simple).

The easiest way to get around it is to simply create two different packages. Or if you want to share some code between the two, one library package and two binary packages that depend on the library package.

I don't know how complicated your source structure setup, but the cmake you probably want to look at is the line in CMakeLists.txt:


That one assigns all the .cpp files under the src directory to QT_SOURCES and uses them to build the qt program. It's collecting the sources for both your mains together. Instead of globbing for sources, just comment that and assign sources manually. e.g.

set(QT_SOURCES src/main.cpp src/qnode.cpp src/main_window.cpp)
set(OTHER_SOURCES src/other_main.cpp)
rosbuild_add_executable(qfoo ${QT_SOURCES} ${QT_RESOURCES_CPP} ${QT_FORMS_HPP} ${QT_MOC_HPP})
rosbuild_add_executable(foo ${OTHER_SOURCES}) # non qt node

If you don't mind really learning the cmake though - check the qt_tutorials package for a complicated example of combining a build of a library and several nodes in the one package.

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Perfect! That's exactly what I needed. I am planning on learning cmake for sure, but I wanted to try and fix this as soon as possible.

pmwalk gravatar image pmwalk  ( 2012-02-28 08:15:40 -0500 )edit

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Asked: 2012-02-27 18:59:44 -0500

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Last updated: Feb 27 '12