further progress on --gc:v2

tools/heapdump2dot.nim

@@ -0,0 +1,66 @@
+
+include prelude
+
+proc main(input, output: string) =
+  type NodeKind = enum
+    local, localInvalid, global, globalInvalid
+  #c_fprintf(file, "%s %p %d rc=%ld color=%c\n",
+  #          msg, c, kind, c.refcount shr rcShift, col)
+  # cell  0x10a908190 22 rc=2 color=w
+  var i, o: File
+  var roots = initTable[string, NodeKind]()
+  if open(i, input):
+    if open(o, output, fmWrite):
+      o.writeLine("digraph $1 {\n" % extractFilename(input))
+      var currNode = ""
+      for line in lines(i):
+        let data = line.split()
+        if data.len == 0: continue
+        case data[0]
+        of "end":
+          currNode = ""
+        of "cell":
+          currNode = data[1]
+          let rc = data[3].substr("rc=".len)
+          let col = case data[4].substr("color=".len)
+                    of "b": "black"
+                    of "w": "green"
+                    of "g": "grey"
+                    else: ""
+          o.write("N" & currNode)
+          if currNode in roots:
+            let v = roots[currNode]
+            case v
+            of local: o.write(" [label=\"local \\N\" fillcolor=$1]" % col)
+            of localInvalid: o.write(" [label=\"local invalid \\N\" fillcolor=$1]" % col)
+            of global: o.write(" [label=\"global \\N\" fillcolor=$1]" % col)
+            of globalInvalid: o.write(" [label=\"global invalid \\N\" fillcolor=$1]" % col)
+          else:
+            o.write(" [fillcolor=$1]" % col)
+          o.writeLine(";")
+        of "child":
+          assert currNode.len > 0
+          o.writeLine("N$1 -> N$2;" % [currNode, data[1]])
+        of "global_root":
+          roots[data[1]] = global
+        of "global_root_invalid":
+          roots[data[1]] = globalInvalid
+        of "onstack":
+          roots[data[1]] = local
+        of "onstack_invalid":
+          roots[data[1]] = localInvalid
+        else: discard
+      close(i)
+      o.writeLine("\n}")
+      close(o)
+    else:
+      quit "error: cannot open " & output
+  else:
+    quit "error: cannot open " & input
+
+if paramCount() == 1:
+  main(paramStr(1), changeFileExt(paramStr(1), "dot"))
+elif paramCount() == 2:
+  main(paramStr(1), paramStr(2))
+else:
+  quit "usage: heapdump2dot inputfile outputfile"