proc,dwarf/godwarf: support parametric types with dictionaries

Change debug_info type reader and proc to convert parametric types into
their real types by reading the corresponding dictionary entry and
using the same method used for interfaces to retrieve the DIE from a
runtime._type address.

'2586e9b1'.

pkg/proc/types.go

@@ -174,6 +174,34 @@ func runtimeTypeToDIE(_type *Variable, dataAddr uint64) (typ godwarf.Type, kind
 	return typ, kind, nil
 }
 
+// resolveParametricType returns the real type of t if t is a parametric
+// type, by reading the correct dictionary entry.
+func resolveParametricType(tgt *Target, bi *BinaryInfo, mem MemoryReadWriter, t godwarf.Type, dictAddr uint64) (godwarf.Type, error) {
+	ptyp, _ := t.(*godwarf.ParametricType)
+	if ptyp == nil {
+		return t, nil
+	}
+	if dictAddr == 0 {
+		return ptyp.TypedefType.Type, errors.New("parametric type without a dictionary")
+	}
+	rtypeAddr, err := readUintRaw(mem, dictAddr+uint64(ptyp.DictIndex*int64(bi.Arch.PtrSize())), int64(bi.Arch.PtrSize()))
+	if err != nil {
+		return ptyp.TypedefType.Type, err
+	}
+	runtimeType, err := bi.findType("runtime._type")
+	if err != nil {
+		return ptyp.TypedefType.Type, err
+	}
+	_type := newVariable("", rtypeAddr, runtimeType, bi, mem)
+
+	typ, _, err := runtimeTypeToDIE(_type, 0)
+	if err != nil {
+		return ptyp.TypedefType.Type, err
+	}
+
+	return typ, nil
+}
+
 type nameOfRuntimeTypeEntry struct {
 	typename string
 	kind     int64