Feature Spotlight: Pretty-printing in the gdb Debugger
A little known feature that adds a lot of convenience for developers on Linux is the pretty-printing of OPC UA data types. It reduces visual noise and makes the introspection of local variables much more convenient.
Pretty-printing can be activated by loading the definitions as
Below are some before/after examples to showcase the effect.
NodeIds have four different representations (numeric, string, guid, bytestring). This leads to a very cluttered gdb output due to the C-union where a numeric id is also interpreted as a (string) pointer.
With pretty-printing enabled, the NodeId is converted as a human-readable string. This is the standard-defined format that can also be parsed via UA_NodeId_parse.
Another complicated datatype is UA_Variant. A variant is a container that can wrap any other OPC UA data type, also as a (multi-dimensional) array. Printing a variant in GDB leads to a messy output. Particularly the data type information is not automatically resolved. Furthermore, the value is hidden behind an opaque void-pointer.
The variant is immediately understandable with pretty-printing enabled. In this example, the variant contains a scalar timestamp value.
@Author Dr. -Ing. Julius Pfrommer, 2021