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update doc for rmw_get_node_names to mention potential null values #214

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Mar 30, 2018
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update doc for rmw_get_node_names to mention potential null values #214

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1 change: 1 addition & 0 deletions rcl/include/rcl/graph.h
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Original file line number Diff line number Diff line change
Expand Up @@ -166,6 +166,7 @@ rcl_names_and_types_fini(rcl_names_and_types_t * names_and_types);
* The node_names parameter must be allocated and zero initialized.
* The node_names is the output for this function, and contains
* allocated memory.
* Note that entries in the array might contain `NULL` value.
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Just curious, what causes an entry to have a NULL value?

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A participant without a "ROS node name" will result in a NULL value. That can e.g. happen when the DDS implementation has some entities running all the time or is there is a vanilla DDS participant which doesn't have a node name defined in ROS.

* Use rcutils_get_zero_initialized_string_array() for initializing an empty
* rcutils_string_array_t struct.
* This node_names struct should therefore be passed to rcutils_string_array_fini()
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