Make loaned messages const on the subscription side #992
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Signed-off-by: Nikolai Morin <[email protected]>
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Can somebody help me understand why the Rpr__rcl__ubuntu_jammy_amd64 check is red? I'm not familiar with Jenkins, and in the console log it says "0 tests failed". |
It's because there are compiler warnings: https://build.ros2.org/job/Rpr__rcl__ubuntu_jammy_amd64/52/gcc/new/ |
Thanks. I'll get on it. |
Signed-off-by: Nikolai Morin <[email protected]>
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Should I also do this change in the rmw layer? |
Yes, and after that it would be nice to cleanup the casts that will become unnecessary here. |
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@nnmm there are some build failures related to the change. |
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@ivanpauno I'm not sure how this can be tested, but it needs the changes to rclcpp as well. |
ah sorry, my bad. |
| @@ -630,7 +630,8 @@ rcl_take_loaned_message( | |||
| // Call rmw_take_with_info. | |||
| bool taken = false; | |||
| rmw_ret_t ret = rmw_take_loaned_message_with_info( | |||
| subscription->impl->rmw_handle, loaned_message, &taken, message_info_local, allocation); | |||
| subscription->impl->rmw_handle, (void **) loaned_message, &taken, message_info_local, | |||
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It seems to me that rather than doing this cast here, we should first change rmw_take_loaned_message_with_info to take a const void ** loaned_message. At that point, everything will be const and no casts will be needed.
Same goes below for rmw_return_loaned_message_from_subscription.
It seems to me that it is an error for the receiver of a loaned message to modify it – other subscriptions could be reading the same message at the same time. Therefore, this PR makes the API stricter by handing out only const pointers.
I have also made corresponding changes in rclcpp, which I'll open a PR for as well and link here.