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What happens if I use c++ 17 features in my ros nodes?

asked 2020-01-09 05:31:12 -0600

max11gen gravatar image

In the ROS manual/wiki you can see, that ROS is only made for C++11. But what exactly does that mean? What happens if I just put add_compile_options(-std=c++17) in the CMakeLists.txt of my ROS-package and use C++17-features anyway? Specifically: Is it possible to use parallel std::for_each from C++17 in my ROS-nodes?

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In the ROS manual/wiki you can see

please always link to pages you are referring to. Right now we don't know what you "see" exactly.

gvdhoorn gravatar imagegvdhoorn ( 2020-01-09 06:36:08 -0600 )edit

@gvdhoorn I know, sorry. The thing was just, that I couldn't actually find where exactly I had read that, but I rather just had it in the back of my head.

max11gen gravatar imagemax11gen ( 2020-01-09 08:13:52 -0600 )edit

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answered 2020-01-09 06:35:18 -0600

gvdhoorn gravatar image

ROS is only made for C++11

this is actually not really true.

For ROS 1: Melodic has lifted the max version to C++14 (see here).

For ROS 2: all ROS 2 versions target C++14 by default (see REP-2000, search for "Minimum language requirements").

What happens if I just put add_compile_options(-std=c++17) in the CMakeLists.txt of my ROS-package and use C++17-features anyway?

Nothing. It probably will just work, as long as your C++17 object code is ABI compatible with whatever libraries you are linking against.

In other words: you'll potentially run into the exact same problems you could have with ABI incompatibilities between libraries when not using ROS.

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Thanks for your answer. But how can I find out, if the object code is ABI compatible after all? Will I get errors if the compatibility is not given, or can it happen that there will be just arbitrary, undefined behaviour occurring?

max11gen gravatar imagemax11gen ( 2020-01-09 08:12:36 -0600 )edit

Yes, could be linking errors, could also be SEGFAULTs. I can't give you a more definitive answer unfortunately.

As I wrote: there is nothing really ROS specific here. It's essentially plain C++.

From my own personal experience though: C++03 + C++11 was troublesome (std::string etc). C++11 and newer has not been a problem for me so far (ie: combining binary artefacts compiled with these different versions). But again: personal experience, so this is not a guarantee everything will work.

gvdhoorn gravatar imagegvdhoorn ( 2020-01-09 08:16:10 -0600 )edit
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In addition to above-mentioned, you can also use the set_properties macro in CMakeLists to set cpp standards for specific targets only (where you know you need c++17 for example) within a package instead for the whole package as it is done with add_compile_options. Here is an example which applies the c++17 standard for a defined executable:

set_property(TARGET my_executable PROPERTY CXX_STANDARD 17)
set_property(TARGET my_executable PROPERTY CXX_STANDARD_REQUIRED ON)
pavel92 gravatar imagepavel92 ( 2020-01-09 08:58:10 -0600 )edit

@gvdhoorn Alright, thanks for your help!

max11gen gravatar imagemax11gen ( 2020-01-09 09:51:35 -0600 )edit

@pavel92 Great hint, thanks.

max11gen gravatar imagemax11gen ( 2020-01-09 09:51:57 -0600 )edit

I would use target_compile_features(..) with a meta-feature instead, but it depends on your CMake version whether that is available.

gvdhoorn gravatar imagegvdhoorn ( 2020-01-09 10:14:57 -0600 )edit

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Asked: 2020-01-09 05:31:12 -0600

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Last updated: Jan 09