%Warning-MODDUP: t/t_mod_dup_bad.v:13:8: Duplicate declaration of module: 'a'
module a();
       ^
                 t/t_mod_dup_bad.v:6:8: ... Location of original declaration
module a();
       ^
                 ... Use "/* verilator lint_off MODDUP */" and lint_on around source to disable this message.
%Warning-MULTITOP: t/t_mod_dup_bad.v:16:8: Multiple top level modules
                                         : ... Suggest see manual; fix the duplicates, or use --top-module to select top.
                                         : ... Top module 'test'
module test();
       ^~~~
                                         : ... Top module 'b'
module b();
       ^
%Error: Exiting due to