Verilator

The tests in a generate conditional block always appear to succeed. The attached example modulegen.v contains two such conditional blocks, only the first of which should be generated. In fact both are generated, leading to an error due to a missing module.

module foobar
  #( parameter
     FOO_START = 0,
     FOO_NUM = 2,
     FOO_TYPE = 0  // This means we should instatiate foo0
     )
    (
    input wire[FOO_NUM-1:0] foo, 
    output wire[FOO_NUM-1:0] bar);

   generate
      begin: g
         genvar j;
         for (j = FOO_START; j < FOO_NUM+FOO_START; j = j + 1)
           begin: foo_inst;
              if (FOO_TYPE == 0)
                begin: foo_0
                   // instatiate foo0
                   foo0 i_foo(.x(foo[j]), .y(bar[j]));
                end
              if (FOO_TYPE == 1)
                begin: foo_1
                   // instatiate foo1
                   foo1 i_foo(.x(foo[j]), .y(bar[j]));
                end
           end // block: foo_inst;
      end // block: g
   endgenerate
endmodule // foobar

module foo0(input wire x, output wire y);

   assign y = ~x;

endmodule

We build with verilator:

verilator -cc --language 1364-2001 --top-module foobar modulegen.v

The error message is:

$ verilator -cc --language 1364-2001 --top-module foobar modulegen.v
%Error: modulegen.v:31: Cannot find file containing module: foo1
%Error: modulegen.v:31: Looked in:
%Error: modulegen.v:31:       foo1
%Error: modulegen.v:31:       foo1.v
%Error: modulegen.v:31:       foo1.sv
%Error: modulegen.v:31:       obj_dir/foo1
%Error: modulegen.v:31:       obj_dir/foo1.v
%Error: modulegen.v:31:       obj_dir/foo1.sv
%Error: Exiting due to 8 warning(s)
%Error: Command Failed $VERILATOR_ROOT/verilator_bin -cc --language 1364-2001 --top-module foobar modulegen.v

This shows that the second conditional block has been generated, which it should not, because FOO_TYPE is 0.

Found with Verilator 3.824.