debuginfo: Add python formatters that allow LLDB to print values with Rust syntax

Author: michaelwoerister

src/etc/lldb_rust_formatters.py

@@ -0,0 +1,232 @@
+# Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+# file at the top-level directory of this distribution and at
+# http://rust-lang.org/COPYRIGHT.
+#
+# Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+# http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+# <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+# option. This file may not be copied, modified, or distributed
+# except according to those terms.
+
+import lldb
+
+def print_val(val, internal_dict):
+  '''Prints the given value with Rust syntax'''
+  type_class = val.GetType().GetTypeClass()
+
+  if type_class == lldb.eTypeClassStruct:
+    return print_struct_val(val, internal_dict)
+
+  if type_class == lldb.eTypeClassUnion:
+    return print_enum_val(val, internal_dict)
+
+  if type_class == lldb.eTypeClassPointer:
+    return print_pointer_val(val, internal_dict)
+
+  if type_class == lldb.eTypeClassArray:
+    return print_fixed_size_vec_val(val, internal_dict)
+
+  return val.GetValue()
+
+
+#=--------------------------------------------------------------------------------------------------
+# Type-Specialized Printing Functions
+#=--------------------------------------------------------------------------------------------------
+
+def print_struct_val(val, internal_dict):
+  '''Prints a struct, tuple, or tuple struct value with Rust syntax'''
+  assert val.GetType().GetTypeClass() == lldb.eTypeClassStruct
+
+  if is_vec_slice(val):
+    return print_vec_slice_val(val, internal_dict)
+  else:
+    return print_struct_val_starting_from(0, val, internal_dict)
+
+def print_vec_slice_val(val, internal_dict):
+  output = "&["
+
+  length = val.GetChildAtIndex(1).GetValueAsUnsigned()
+
+  data_ptr_val = val.GetChildAtIndex(0)
+  data_ptr_type = data_ptr_val.GetType()
+  assert data_ptr_type.IsPointerType()
+
+  element_type = data_ptr_type.GetPointeeType()
+  element_type_size = element_type.GetByteSize()
+
+  start_address = data_ptr_val.GetValueAsUnsigned()
+
+  for i in range(length):
+    address = start_address + i * element_type_size
+    element_val = val.CreateValueFromAddress( val.GetName() + ("[%s]" % i), address, element_type )
+    output += print_val(element_val, internal_dict)
+
+    if i != length - 1:
+      output += ", "
+
+  output += "]"
+  return output
+
+def print_struct_val_starting_from(field_start_index, val, internal_dict):
+  '''
+  Prints a struct, tuple, or tuple struct value with Rust syntax.
+  Ignores any fields before field_start_index.
+  '''
+  assert val.GetType().GetTypeClass() == lldb.eTypeClassStruct
+
+  t = val.GetType()
+  has_field_names = type_has_field_names(t)
+  type_name = extract_type_name(t.GetName())
+  output = ""
+
+  if not type_name.startswith("("):
+    # this is a tuple, so don't print the type name
+    output += type_name
+
+  if has_field_names:
+    output += " { \n"
+  else:
+    output += "("
+
+  num_children = val.num_children
+
+  for child_index in range(field_start_index, num_children):
+    if has_field_names:
+      field_name = t.GetFieldAtIndex(child_index).GetName()
+      output += field_name + ": "
+
+    field_val = val.GetChildAtIndex(child_index)
+    output += print_val(field_val, internal_dict)
+
+    if child_index != num_children - 1:
+      output += ", "
+
+    if has_field_names:
+      output += "\n"
+
+  if has_field_names:
+    output += "}"
+  else:
+    output += ")"
+
+  return output
+
+
+def print_enum_val(val, internal_dict):
+  '''Prints an enum value with Rust syntax'''
+
+  assert val.GetType().GetTypeClass() == lldb.eTypeClassUnion
+
+  if val.num_children == 1:
+    first_variant_name = val.GetChildAtIndex(0).GetName()
+    if first_variant_name and first_variant_name.startswith("RUST$ENCODED$ENUM$"):
+      # Try to extract the
+
+      last_separator_index = first_variant_name.rfind("$")
+      if last_separator_index == -1:
+        return "<invalid enum encoding: %s>" % first_variant_name
+
+      second_last_separator_index = first_variant_name.rfind("$", 0, last_separator_index)
+      if second_last_separator_index == -1:
+        return "<invalid enum encoding: %s>" % first_variant_name
+
+      try:
+        disr_field_index = first_variant_name[second_last_separator_index + 1 :
+                                              last_separator_index]
+        disr_field_index = int(disr_field_index)
+      except:
+        return "<invalid enum encoding: %s>" % first_variant_name
+
+      disr_val = val.GetChildAtIndex(0).GetChildAtIndex(disr_field_index).GetValueAsUnsigned()
+
+      if disr_val == 0:
+        null_variant_name = first_variant_name[last_separator_index + 1:]
+        return null_variant_name
+      else:
+        return print_struct_val_starting_from(0, val.GetChildAtIndex(0), internal_dict)
+    else:
+      return print_struct_val_starting_from(0, val.GetChildAtIndex(0), internal_dict)
+
+  # extract the discriminator value by
+  disr_val = val.GetChildAtIndex(0).GetChildAtIndex(0)
+  disr_type = disr_val.GetType()
+
+  if disr_type.GetTypeClass() != lldb.eTypeClassEnumeration:
+    return "<Invalid enum value encountered: Discriminator is not an enum>"
+
+  variant_index = disr_val.GetValueAsUnsigned()
+  return print_struct_val_starting_from(1, val.GetChildAtIndex(variant_index), internal_dict)
+
+
+def print_pointer_val(val, internal_dict):
+  '''Prints a pointer value with Rust syntax'''
+  assert val.GetType().IsPointerType()
+  sigil = "&"
+  type_name = extract_type_name(val.GetType().GetName())
+  if type_name and type_name[0:1] in ["&", "~", "*"]:
+    sigil = type_name[0:1]
+
+  return sigil + hex(val.GetValueAsUnsigned()) #print_val(val.Dereference(), internal_dict)
+
+
+def print_fixed_size_vec_val(val, internal_dict):
+  assert val.GetType().GetTypeClass() == lldb.eTypeClassArray
+
+  output = "["
+
+  for i in range(val.num_children):
+    output += print_val(val.GetChildAtIndex(i), internal_dict)
+    if i != val.num_children - 1:
+      output += ", "
+
+  output += "]"
+  return output
+
+
+#=--------------------------------------------------------------------------------------------------
+# Helper Functions
+#=--------------------------------------------------------------------------------------------------
+
+unqualified_type_markers = frozenset(["(", "[", "&", "*"])
+
+def extract_type_name(qualified_type_name):
+  '''Extracts the type name from a fully qualified path'''
+  if qualified_type_name[0] in unqualified_type_markers:
+    return qualified_type_name
+
+  end_of_search = qualified_type_name.find("<")
+  if end_of_search < 0:
+    end_of_search = len(qualified_type_name)
+
+  index = qualified_type_name.rfind("::", 0, end_of_search)
+  if index < 0:
+    return qualified_type_name
+  else:
+    return qualified_type_name[index + 2:]
+
+
+def type_has_field_names(ty):
+  '''Returns true of this is a type with field names (struct, struct-like enum variant)'''
+  # This may also be an enum variant where the first field doesn't have a name but the rest has
+  if ty.GetNumberOfFields() > 1:
+    return ty.GetFieldAtIndex(1).GetName() != None
+  else:
+    return ty.GetFieldAtIndex(0).GetName() != None
+
+
+def is_vec_slice(val):
+  ty = val.GetType()
+  if ty.GetTypeClass() != lldb.eTypeClassStruct:
+    return False
+
+  if ty.GetNumberOfFields() != 2:
+    return False
+
+  if ty.GetFieldAtIndex(0).GetName() != "data_ptr":
+    return False
+
+  if ty.GetFieldAtIndex(1).GetName() != "length":
+    return False
+
+  type_name = extract_type_name(ty.GetName()).replace("&'static", "&").replace(" ", "")
+  return type_name.startswith("&[") and type_name.endswith("]")