This Chisel code works ok:
chiselMainTest(Array[String]("--backend", "c", "--genHarness"), () => Module( new Cache(nways = 16, nsets = 32) )){c => new CacheTests(c)}
However this one - a small variation - produces run-time error:
val cache_inst = new Cache(nways = 16, nsets = 32)
chiselMainTest(Array[String]("--backend", "c", "--genHarness"), () => Module(cache_inst)){c => new CacheTests(c)}
[error] (run-main) java.util.NoSuchElementException: head of empty list
java.util.NoSuchElementException: head of empty list
at scala.collection.immutable.Nil$.head(List.scala:337)
at scala.collection.immutable.Nil$.head(List.scala:334)
Any instantiation of a module must be wrapped with "Module()".
This is just a guess, but give this a try:
The reason for this, IIRC, is that "Module()" helps Chisel understand the parentage of wires/objects created within your Cache object (essentially pushing and popping the Module stack as the graph is constructed).