Assume x values for missing signal data in FST #4627
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What are the reasons/motivation for this change?
Handle cases where signal data is missing in FST files during simulation. Previously, when a signal ID was not found in past_data, it would cause an error. This patch ensures that missing signal data is assumed to be undefined ('x'), which aligns with the behaviour of
gtkwave
. Below is a screenshot of howgtkwave
interpretstests/sim/simple_assign.vcd
.Explain how this is achieved.
Instead of logging an error when the signal ID is not found, the
valueOf
now returns a string filled with 'x' characters, where the length of the string corresponds to the signal’s width.If applicable, please suggest to reviewers how they can test the change.
Note
I considered adding a warning like:
log_warning("Signal id %d not found, assuming x\n", (int)signal);
but decided against it to avoid extra verbosity. Open to adding it if needed.