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I have the gcc c++0x flag set for a few of my packages. All the packages that depend on these package also needs the c++0x flag if they must not throw warning when the header files are processed.
Is there a way for catkin to export the flags? I saw the CFG_EXTRAS option for catkin_package(), Do I set the CFG_EXTRAS? What does it stand for?
Thanking you, Benzun
You can pass multiple "CMake configuration extra" files via catkin_package(CFG_EXTRAS) to be included when downstream packages find your package:
catkin_package(
CFG_EXTRAS ${PROJECT_NAME}-extras.cmake
)
An example for such a file would be cmake/${PROJECT_NAME}-extras.cmake:
# for older versions of clang, libstdc++ is used by default and we need to explicitly request libc++ instead
if(APPLE)
set(CMAKE_CXX_FLAGS "-std=c++0x -stdlib=libc++ ${CMAKE_CXX_FLAGS}")
else()
set(CMAKE_CXX_FLAGS "-std=c++0x ${CMAKE_CXX_FLAGS}")
endif ()
I think the cmake file must be saved with the ".in" extension i.e. cmake/$PROJECT_NAME-extras.cmake.in. I couldn't get it to work with just .cmake
Using only the extension ".cmake" is supported. E.g. the following package does exactly that: https://github.com/ros/class_loader
Not really an answer (I do think you can use CFG_EXTRAS for this btw), but afaik packages are not supposed to to use (or at least, I think it will not be releasable) anything but C++03 (from REP3, Rationale, C++):
We use the C++03 (ISO/IEC 14882:2003) standard [..]
Use of C++[0|1]x or tr1 features are only allowed if support for that feature is checked at compile time, and equivalent functionality exists without requiring C++[0|1]x code. A wholesale jump to C++[0|1]x will not happen until all commonly used OS platforms fully support it.
There have been numerous questions regarding updating REP3 though, see for instance Revisit REP3 with respect to C++11?.
Edit: CFG_EXTRAS expects to be passed a path to a file (see the catkin_package() doc). This file may contain any combination of valid CMake statements. You could for instance set(..) a MY_PKG_CXX_FLAGS or similar, which exports your specific flags. The contents of the file is automatically loaded whenever someone depends on your package (ie, via find_package(YOUR_PKG) or as a component in find_package(catkin REQUIRED COMPONENTS ..)).
All they would then have to do would be to append your flags to the CMAKE_CXX_FLAGS for instance.
PS: it might be worthwhile to check whether CMake or catkin has some best practices defined regarding naming of .._CXX_FLAGS and / or appending to the CMAKE_CXX_FLAGS variable(s).
I agree in principle, but I've noticed that a lot of the time having to implement things twice (once for C++01 and once without) incurs significant overhead, to the point where it can sometimes negate the benefits of using any advanced features in the first place.
Asked: 2014-06-18 12:51:51 -0500
Seen: 2,573 times
Last updated: Jun 18 '14
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