hw-cbmc: re-enable --vcd#2008
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July 16, 2026 12:49
The --vcd option was parsed but had no effect: show_unwind_trace() was only reachable via CBMC's old error_trace() callback mechanism, which no longer exists since hw-cbmc moved to the goto_verifiert pipeline. The option now enables trace storage in the verifier, and on VERIFICATION FAILED the stored goto trace is converted into a hardware trans_tracet by collecting the values of the timeframe-instantiated signals (identifier@t), which is then written using the existing show_trans_trace_vcd(). This is independent of the front-end's module naming. The dead do_unwind_module()/error_trace() code is removed. Fixes: #1955 Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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The
--vcdoption was parsed but had no effect, as reported in #1955:show_unwind_trace()was only reachable via CBMC's olderror_trace()callback mechanism, which no longer exists since hw-cbmc moved to thegoto_verifiertpipeline, leaving it (anddo_unwind_module()) as dead code.Changes:
--vcdnow enables trace storage in the verifier (a--vcdrun hence also prints the trace, as with--trace).trans_tracetby collecting the values of the timeframe-instantiated signals (identifier@t), and written using the existingshow_trans_trace_vcd(). This is independent of the front-end's module naming.do_unwind_module()/error_trace()code is removed.hw-cbmc/VCD1checks the VCD output for a counter with a failing assertion.As before, the VCD covers all timeframes up to the bound; the failing timeframe is not marked.
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