[Iverilog-devel] The string type and $value$plusargs

[<ni...@ly...>]

I'm now trying to read a memory dump, using a command line argument for
the file name (as hinted at the end of
http://iverilog.wikia.com/wiki/Simulation).

System verilog has a string type, so I tried this program,

  module main;
     reg [64:0] mem [0:100];
     string img;
     initial begin
        if (!$value$plusargs("img=%s", img)) begin
           $display("Specify image file with +img=<image>.");
           $finish_and_return(1);
        end
        $display("Using image: %s", img);
        $readmemh(img, mem);      
        $display("Initial memory word: mem[0] = %x", mem[0]);
        $finish;
     end
  endmodule // main

I compile using

  $ iverilog -g2005-sv main.vl -o main

(with iverilog compiled from git eariler today). Works fine, so far. But
running it fails,

  $ ./main +img=../examples/hello.hex
  ERROR: main.vl:5: $value$plusargs's second argument must be a variable, found a vpiStringVar.

If I change "string img;" to "reg [300:0] img;" it works, and I get the output

  Using image:                  ../examples/hello.hex
  WARNING: main.vl:10: $readmemh(../examples/hello.hex): Not enough words in the file for the requested range [0:100].
  Initial memory word: mem[0] = 07000b4a08408e500

But that doesn't seem like a very good solution, since I have to put an
arbitrary size on the register, and it will fail with filenames which
exceed this size.

If I try the System verilog support in iverilog (primarily, I would like
to use the interface abstraction), I should be able to use the vlog95
target to generate plain verilog code which I could feed to, e.g.,
yosys, right?

Regards,
/Niels

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