Multi-dimensional arrays in VCD crash wellen

[64]

See https://github.com/gtkwave/gtkwave/issues/304

Some tools will output multi-dimensional arrays in a VCD file:

$var wire 32 x foo[0][0]  $end

Currently this crashes Wellen with a parse error on this line: https://github.com/ekiwi/waveform-rust/blob/7f08ad43a488963d3484b302912593d254304ab2/src/vcd.rs#L351

Full reproducer:

$timescale
    1ps
$end
$scope module logic $end
$var wire 32 x foo[0][0]  $end
$upscope $end
$enddefinitions $end
$dumpvars
#0
0!

[ekiwi]

Do you have any information on which simulator or other tool generates VCDs with multi-dimensional arrays? I couldn't find a specific tool mentioned in the issue that you linked.

[64]

The linked issue indicates that VCS produces such output. Unfortunately the tool I'm using is an internal simulation tool, but GTKWave seems to accept this while wellen dies

[ekiwi]

Just to clarify: You are looking for support for the option where each entry of the multi-dimensional array is represented as a separate variable, correct?

That seems to be the VCS behavior which is described in the issue you linked:

Simulators such as VCS will dump out the elements individually logic [2:0][7:0] a

would be dumped as separate $var entries: a[2][7:0] a[1][7:0] a[0][7:0]

If that is the case, that should be quite doable to support.

While you cannot share your simulator, would you be able to provide us with a more complete test file and give us permission to include it in our test suite? While your example is enough to make wellen crash, it would be nice to have a larger "real" file to test the complete support on.

Thanks for opening this issue!

[64]

I probably can't share the actual dump that I was looking at locally, since it contains a lot of details about some very proprietary bit of hardware :sweat_smile:, but next week I'll try to make a more complete reproduction that could be included in a test here

I also run into a few other crashes, possibly from other places where the tool does not spit out something strictly according to the VCD spec, and will look into those further

[ekiwi]

but next week I'll try to make a more complete reproduction that could be included in a test here

That would be awesome!

In general I am interested in supporting output from as many tools as possible, doesn't matter whether they conform to the (paywalled) VCD standard or not. I do prioritize working on tools depending on the number of users and also on whether they are open-source.

If you can provide me with some example VCDs that I can open in GTKWave to see what you want them to be rendered like, there is a good chance I will find some time over the next couple of weeks to add support to wellen.

[ekiwi]

It is possible that your issue is fixed with the latest wellen release. Please try out Surfer once this PR is merged and let me know: https://gitlab.com/surfer-project/surfer/-/merge_requests/332

[ekiwi]

And it was merged. Please check out the latest surfer (compiled from the main branch) and if it still crashes, please re-open this issue.