On 2010-12-12, a local commit was made: "latch synthesis fix: Connect q and data pins in netlist." Testing had shown that FNF output was more correct than before this commit, but the changes were causing new ivtest failures. Exploration was begun into some apparent issues with the FNF, which was ultimately proven to be perfect, and the ivtest failures (basiclatch) were determined to be VVP-related.
Meanwhile, a parallel effort was initiated to resolve the VVP issues. That effort resulted in several patches since 2010-12-12, some of which were in the same area as the latch synthesis fix mentioned above. In fact, those patches obsoleted the 2010-12-12 local commit as described.
However, there were certain robustness improvements included in that local commit that were not obsoleted. After a pull, manual conflict resolution and thorough testing, those improvements are preserved by this patch and are as follows:
Check for zero-width vector.
Replace assertions with exceptions.
Use C++-style cast.
Use suffix for unsigned integer constants.
Catch bad_alloc exception.
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