New Yosys version results in fatal errors when linting with Verilator.

[zapta]

Recently we upgraded from oss-cad-suite 2025-09-23 to 2026-01-24 (latest) and this broke our ability to lint Yosys project using verilator. With older versions of Yosys we got many warnings from Yosys's libraries but were able to suppress them using a verilator config file. With the latest version we get fatal errors which we can't suppress.

Any help will be greatly appreciated. We are also open for switching to a different linter that is know to be Yosys friendly.

Verilator command line

verilator_bin --lint-only --quiet --bbox-unsup --timing \
    -Wno-TIMESCALEMOD -Wno-MULTITOP -DAPIO_SIM=0 \
    --top-module ledon \
    -I/Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5 \
    _rules.vlt \
    /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_sim.v 
    /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v \
    ledon.v

Some of the new errors we get

%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:4:13: syntax error, unexpected '.', expecting '['
    4 | module GSR (...);
      |             ^
        ... See the manual at https://verilator.org/verilator_doc.html?v=5.041 for more assistance.
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:9:13: syntax error, unexpected '.', expecting '['
    9 | module PUR (...);
      |             ^
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:11:5: syntax error, unexpected input
   11 |     input PUR;
      |     ^~~~~
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:15:14: syntax error, unexpected '.', expecting '['
   15 | module SGSR (...);
      |              ^
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:21:18: syntax error, unexpected '.', expecting '['
   21 | module PDPW16KD (...);
      |                  ^
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:97:5: syntax error, unexpected input
   97 |     input DI35;
      |     ^~~~~
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:211:20: syntax error, unexpected '.', expecting '['
  211 | module MULT18X18D (...);
      |                    ^
%Error: /Users/user/Downloads/oss-cad-suite-2026-01-24/share/yosys/ecp5/cells_bb.v:237:5: syntax error, unexpected input
  237 |     input A17;
      |     ^~~~~

The full project to reproduce the problem, adjust the oss-cad-suite directory in run.sh.
work-verilator.zip

[zapta]

... I just found that Verilator is the recommended linter for Yosys project. Are Yosys's libraries tested to pass Verilator linting?

https://github.com/YosysHQ/yosys/blob/main/README.md#additional-information

[whitequark]

I don't think so, no.

[zapta]

Thanks @whitequark,

1. Is it reasonable to file a Yosys feature request to have automatic lint testing of the libraries?

2. Any suggestions how to handle the linting now with the existing libraries?

[whitequark]

I'd propose going through the libraries, fixing any failing lints, and contributing the changes upstream. Since this is going to be a large diff, you should first ask on the Discourse whether your changes would be acceptable (I probably wouldn't be the one to reivew them but others would).

[zapta]

Thanks @whitequark , I started in the users section and will go from there to the developers section https://yosyshq.discourse.group/t/how-do-you-lint-your-yosys-verilog-projects/117

A couple of questions to orient myself with the project

1. Are the yosys standard libs that are released at share/yosys/ecp5/* checked in github in their final form or are they generated by the build workflows? (can you point me to the location(s) in github?)
2. Does Yosys has automatic tests (independent or as part of the build) that can be extended to test also the libraries? (again, can you point me to the location?)
3. Are the libs of the various architectures (ICE40, ECP5, Gowin, etc) handled by the same team or by respective team of each architecture?

[whitequark]

Are the yosys standard libs that are released at share/yosys/ecp5/* checked in github in their final form or are they generated by the build workflows? (can you point me to the location(s) in github?)

Checked in git. Some of these files were at one point generated, but I'm fairly sure nobody even remembers how to do that anymore (and in any case they were manually edited since).

Does Yosys has automatic tests (independent or as part of the build) that can be extended to test also the libraries? (again, can you point me to the location?)

See tests/.

Are the libs of the various architectures (ICE40, ECP5, Gowin, etc) handled by the same team or by respective team of each architecture?

There are no permanent "architecture teams" to do such a thing.

[zapta]

This breakage is due to this PR https://github.com/YosysHQ/yosys/pull/3908/files#diff-c70f4d09772dc7f4df4a9ba257d9f228439ba412c453085eac183ab79dc1060a which changed the content of the file share/yosys/ecp5/cells_bb.v in the built package.

[zapta]

Hi @whitequark, I posted a question in the developers section here https://yosyshq.discourse.group/t/proposal-automatic-test-for-yosys-cell-libraries/118 , please fell free to respond there.