gEDA-user: Trying to figure out VCDs with Icarus and GTKWave

[Joshua Boyd <jdboyd@jdboyd.net>]

When I compile and execute the following file:

module main;
reg [3:0] a;
reg [3:0] b;
initial
	begin
	a = 0;
	b = 0;
	while (1)
	      begin
		b = a;
		a = a + 1;	
		#10;
	      end
	end
initial
	begin
	$dumpfile("file.vcd"); // Dump output file.
	$dumpvars(1, a, b);

	#1000;
	$finish;
end
endmodule

It creates file.vcd, which is 3339 bytes.

When I open file.vcd in gtkwave (version 1.3.24), in the little status
area in the upper left it says:
VCD loaded successfully.
[2] facilities found.
[200] regions found.

However, in the signals pain, it should time, but it doesn't list either
signal a or b.  I've tried several different arrangements, like
switching the order of the $dump statements in the file, or doing
$dumpvars; instead of $dumpvars(1, a, b);, but nothing I do seems to
result in the vcd file showing signals in gtkwave.  I figure this has
got to be something stupid, but I'm stuck.