%Warning-CONSTRAINTIGN: t/t_std_randomize_unsup_bad.v:10:16: std::randomize ignored (unsupported) : ... note: In instance 't' 10 | if (std::randomize(a, b) != 1) $stop; | ^~~~~~~~~ ... For warning description see https://verilator.org/warn/CONSTRAINTIGN?v=latest ... Use "/* verilator lint_off CONSTRAINTIGN */" and lint_on around source to disable this message. %Warning-CONSTRAINTIGN: t/t_std_randomize_unsup_bad.v:11:16: std::randomize ignored (unsupported) : ... note: In instance 't' 11 | if (std::randomize(a, b) with { 2 < a; a < 7; b < a; } != 1) $stop; | ^~~~~~~~~ %Error: Exiting due to