error "OpenCV 4.x+ requires enabled C++11 support"

[Hagaik92]

Hello,
Im trying to run darknet_ros and get this message:

/usr/include/opencv4/opencv2/core/cvdef.h:690:4: error: #error "OpenCV 4.x+ requires enabled C++11 support"

Im using a Jetson Xavier NX with jetpack 4.4.1
i have tried downgrading my opencv version to 3.4.0 but nothing changed.
any solutions? also, if someone has managed to run darknet_ros over xavier i would like to try his configurations.
Thanks!

[bigrobinson]

I had the same problem. If you search on this problem in the issues you'll find a lot about it. I solved it by cloning a fork from @kunaltyagi. Disclaimers: I have built it without errors but not yet used it in my implementation. His fork has not been updated as recently as the repo here (though neither include very recent work). He has converted the c code to cpp. I don't know what if any performance difference this implies.

cd catkin_ws/src
git clone --recursive https://github.com/kunaltyagi/darknet_ros.git

Take a look at the available branches, choose build for OpenCV4, and do a recursive update of the submodule to insure you get Darknet.

git branch -a
git checkout remotes/origin/opencv4
git submodule update --recursive

Going into the darknet_ros top level CMakeLists.txt, set your compute architecture and correct the path to the cuda library (or you'll get a linker error):

• In the set function at line 20:
  -gencode arch=compute_72,code=sm_72

• In linkdirectories lib --> lib64
  ${CUDA_TOOLKIT_ROOT_DIR}/lib64

Finally, build as instructed in the readme.
catkin_make -DCMAKE_BUILD_TYPE=Release

[kunaltyagi]

@bigrobinson I've been having trying to switch to the the AlexyAB fork, which is much more active for the darknet repo, but am having linker issues with that.

I was happy enough with the OpenCV4 port for the original darknet repo, so I just left it there.

WRT performance impacts, I didn't profile, but I think there will be no negative impacts due to change from C to C++. With the same code, the performance shouldn't be affected much (or even unaffected)

[bigrobinson]

Understood @kunaltyagi. I agree performance should not suffer. Thank you so much for your work on this my friend!

[Hagaik92]

I fixed the problem by rebuilding Cv_bridge and downgrade to OpenCV 3.4.0 . it didnt work with any other versions .

[bigrobinson]

Update: I have now successfully run the opencv4 branch I mentioned above and confirmed that it works. In my case I used a Basler camera and the pylon ROS drivers.

[iamrajee]

I fixed the problem by rebuilding Cv_bridge and downgrade to OpenCV 3.4.0 . it didnt work with any other versions .

Can you eloborate the steps? Thanks!