Avoid setting error message twice.

[iuhilnehc-ynos]

Just a minor fix.

$ ./build/rcl_action/test_action_client
...

>>> [rcutils|error_handling.c:108] rcutils_set_error_state()
This error state is being overwritten:

  'failed to allocate memory for action goal service name, at /home/chenlh/Projects/ROS2/ros2-master/src/ros2/rcl/rcl_action/src/rcl_action/names.c:46'

with this new error message:

  'failed to get goal service name, at /home/chenlh/Projects/ROS2/ros2-master/src/ros2/rcl/rcl_action/src/rcl_action/action_client.c:215'

rcutils_reset_error() should be called after error handling to avoid this.
...

There exist two methods to fix,

1. call rcl_reset_error(); before RCL_SET_ERROR_MSG. (the old error message LOST)
2. use RCUTILS_SAFE_FWRITE_TO_STDERR instead of RCL_SET_ERROR_MSG if error already set. (Current PR)

Signed-off-by: Chen Lihui Lihui.Chen@sony.com

[iuhilnehc-ynos]

CI with

ros2.repos
--packages-up-to rcl_action
--packages-select rcl_action

• Linux
• Linux-aarch64
• macOS
• Windows

[iuhilnehc-ynos]

I found there are three ways to deal with an error message.

1. call rcl_reset_error() to ignore the root error message

rcl/rcl_action/src/rcl_action/action_server.c

Lines 898 to 900 in 2883ce4

	if (!rcl_service_is_valid(&action_server->impl->goal_service)) {
	rcl_reset_error();
	RCL_SET_ERROR_MSG("goal service is invalid");

2. not to call rcl_reset_error(), just call RCUTILS_SAFE_FWRITE_TO_STDERR

rcl/rcl/src/rcl/publisher.c

Lines 144 to 147 in 2883ce4

	if (RMW_RET_OK != rmw_fail_ret) {
	RCUTILS_SAFE_FWRITE_TO_STDERR(rmw_get_error_string().str);
	RCUTILS_SAFE_FWRITE_TO_STDERR("\n");
	}

3. use RCUTILS_SAFE_FWRITE_TO_STDERR to encapsulate the rcl_get_error_string().str, and then rcl_reset_error()

rcl/rcl/src/rcl/logging.c

Lines 213 to 216 in 2883ce4

	RCUTILS_SAFE_FWRITE_TO_STDERR("failed to finalize char array: ");
	RCUTILS_SAFE_FWRITE_TO_STDERR(rcl_get_error_string().str);
	rcl_reset_error();
	RCUTILS_SAFE_FWRITE_TO_STDERR("\n");

Is there a specific rule?

[iuhilnehc-ynos]

I will update action_client to keep the same processing about RCL_SET_ERROR_MSG consistent with action_server.

[fujitatomoya]

lgtm

[clalancette]

Fine by me with green CI.