Add -Wconversion flag to protect future developments

[gwalck]

When working on joint_limits, I faced an issue with a rclcpp::Duration that I constructed using seconds and nanoseconds, but by mistake used a float 0.005 for the seconds. Since the awaited arguments are ints, the float conversion led to a NULL duration which I did not realize for a too long time.

There was no compilation warning, as -Wall does not include -Wconversion, supposedly to avoid too many warnings.
With that flag the warning looks like this

rolling-ctrl-ws/src/ros2_control/joint_limits/test/test_simple_joint_limiter.cpp:224:29: warning: conversion from ‘double’ to ‘int32_t’ {aka ‘int’} changes value from ‘5.0000000000000001e-3’ to ‘0’ [-Wfloat-conversion]
  224 |     rclcpp::Duration period(0.005, 0);

I tested in ros_control package to add -Wconversion compilation flag which created only 2 warnings, that could be easily fixed with explicit cast.

Hence, for protecting future developments from risky mistakes with conversions, I suggest to add this flag in all packages of the repo. I will provide a similar PR for ros2_controllers that were definitively affected by exactly the same Time-at-zero issue.

[bmagyar]

A welcome addition! Thank you

[codecov-commenter]

Codecov Report

Merging #1053 (cf6ab33) into master (925f5f3) will decrease coverage by 2.27%.
The diff coverage is 35.10%.

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@@            Coverage Diff             @@
##           master    #1053      +/-   ##
==========================================
- Coverage   34.61%   32.34%   -2.27%     
==========================================
  Files          52       93      +41     
  Lines        2981     9793    +6812     
  Branches     1855     6599    +4744     
==========================================
+ Hits         1032     3168    +2136     
- Misses        310      777     +467     
- Partials     1639     5848    +4209     

Flag	Coverage Δ
unittests	32.34% <35.10%> (-2.27%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
controller_manager/src/controller_manager.cpp	38.04% <ø> (-1.67%)	⬇️
controller_manager/src/ros2_control_node.cpp	0.00% <0.00%> (ø)
..._interface/include/hardware_interface/actuator.hpp	100.00% <ø> (ø)
...ce/include/hardware_interface/async_components.hpp	0.00% <0.00%> (ø)
...re_interface/include/hardware_interface/sensor.hpp	100.00% <ø> (ø)
...re_interface/include/hardware_interface/system.hpp	100.00% <ø> (ø)
hardware_interface/src/resource_manager.cpp	47.32% <ø> (-6.30%)	⬇️
hardware_interface/src/sensor.cpp	50.52% <ø> (ø)
hardware_interface/src/system.cpp	55.45% <ø> (ø)
...rface/test/mock_components/test_generic_system.cpp	9.42% <ø> (ø)
... and 70 more

... and 19 files with indirect coverage changes

[christophfroehlich]

merci

[christophfroehlich]

@Mergifyio backport iron humble

[mergify]

backport iron humble

✅ Backports have been created

• #1814 Add -Wconversion flag to protect future developments (backport #1053) has been created for branch iron but encountered conflicts
• #1815 Add -Wconversion flag to protect future developments (backport #1053) has been created for branch humble but encountered conflicts