gdb_rust_pretty_printing.py

# Copyright 2013-2014 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 gdb
import re
import sys
import debugger_pretty_printers_common as rustpp

# We want a version of `range` which doesn't allocate an intermediate list,
# specifically it should use a lazy iterator. In Python 2 this was `xrange`, but
# if we're running with Python 3 then we need to use `range` instead.
if sys.version_info.major >= 3:
    xrange = range

#===============================================================================
# GDB Pretty Printing Module for Rust
#===============================================================================

class GdbType(rustpp.Type):

    def __init__(self, ty):
        super(GdbType, self).__init__()
        self.ty = ty
        self.fields = None

    def get_unqualified_type_name(self):
        tag = self.ty.tag

        if tag is None:
            return tag

        return rustpp.extract_type_name(tag).replace("&'static ", "&")

    def get_dwarf_type_kind(self):
        if self.ty.code == gdb.TYPE_CODE_STRUCT:
            return rustpp.DWARF_TYPE_CODE_STRUCT

        if self.ty.code == gdb.TYPE_CODE_UNION:
            return rustpp.DWARF_TYPE_CODE_UNION

        if self.ty.code == gdb.TYPE_CODE_PTR:
            return rustpp.DWARF_TYPE_CODE_PTR

        if self.ty.code == gdb.TYPE_CODE_ENUM:
            return rustpp.DWARF_TYPE_CODE_ENUM

    def get_fields(self):
        assert ((self.get_dwarf_type_kind() == rustpp.DWARF_TYPE_CODE_STRUCT) or
                (self.get_dwarf_type_kind() == rustpp.DWARF_TYPE_CODE_UNION))
        if self.fields is None:
            self.fields = list(self.ty.fields())
        return self.fields

    def get_wrapped_value(self):
        return self.ty


class GdbValue(rustpp.Value):
    def __init__(self, gdb_val):
        super(GdbValue, self).__init__(GdbType(gdb_val.type))
        self.gdb_val = gdb_val
        self.children = {}

    def get_child_at_index(self, index):
        child = self.children.get(index)
        if child is None:
            gdb_field = get_field_at_index(self.gdb_val, index)
            child = GdbValue(self.gdb_val[gdb_field])
            self.children[index] = child
        return child

    def as_integer(self):
        if self.gdb_val.type.code == gdb.TYPE_CODE_PTR:
            return int(str(self.gdb_val), 0)
        return int(self.gdb_val)

    def get_wrapped_value(self):
        return self.gdb_val


def register_printers(objfile):
    """Registers Rust pretty printers for the given objfile"""
    objfile.pretty_printers.append(rust_pretty_printer_lookup_function)


def rust_pretty_printer_lookup_function(gdb_val):
    """
    Returns the correct Rust pretty printer for the given value
    if there is one
    """

    val = GdbValue(gdb_val)
    type_kind = val.type.get_type_kind()

    if (type_kind == rustpp.TYPE_KIND_REGULAR_STRUCT or
        type_kind == rustpp.TYPE_KIND_EMPTY):
        return RustStructPrinter(val,
                                 omit_first_field = False,
                                 omit_type_name = False,
                                 is_tuple_like = False)

    if type_kind == rustpp.TYPE_KIND_STRUCT_VARIANT:
        return RustStructPrinter(val,
                                 omit_first_field = True,
                                 omit_type_name = False,
                                 is_tuple_like = False)

    if type_kind == rustpp.TYPE_KIND_SLICE:
        return RustSlicePrinter(val)

    if type_kind == rustpp.TYPE_KIND_STR_SLICE:
        return RustStringSlicePrinter(val)

    if type_kind == rustpp.TYPE_KIND_STD_VEC:
        return RustStdVecPrinter(val)

    if type_kind == rustpp.TYPE_KIND_STD_STRING:
        return RustStdStringPrinter(val)

    if type_kind == rustpp.TYPE_KIND_TUPLE:
        return RustStructPrinter(val,
                                 omit_first_field = False,
                                 omit_type_name = True,
                                 is_tuple_like = True)

    if type_kind == rustpp.TYPE_KIND_TUPLE_STRUCT:
        return RustStructPrinter(val,
                                 omit_first_field = False,
                                 omit_type_name = False,
                                 is_tuple_like = True)

    if type_kind == rustpp.TYPE_KIND_CSTYLE_VARIANT:
        return RustCStyleVariantPrinter(val.get_child_at_index(0))

    if type_kind == rustpp.TYPE_KIND_TUPLE_VARIANT:
        return RustStructPrinter(val,
                                 omit_first_field = True,
                                 omit_type_name = False,
                                 is_tuple_like = True)

    if type_kind == rustpp.TYPE_KIND_SINGLETON_ENUM:
        variant = get_field_at_index(gdb_val, 0)
        return rust_pretty_printer_lookup_function(gdb_val[variant])

    if type_kind == rustpp.TYPE_KIND_REGULAR_ENUM:
        # This is a regular enum, extract the discriminant
        discriminant_val = rustpp.get_discriminant_value_as_integer(val)
        variant = get_field_at_index(gdb_val, discriminant_val)
        return rust_pretty_printer_lookup_function(gdb_val[variant])

    if type_kind == rustpp.TYPE_KIND_COMPRESSED_ENUM:
        encoded_enum_info = rustpp.EncodedEnumInfo(val)
        if encoded_enum_info.is_null_variant():
            return IdentityPrinter(encoded_enum_info.get_null_variant_name())

        non_null_val = encoded_enum_info.get_non_null_variant_val()
        return rust_pretty_printer_lookup_function(non_null_val.get_wrapped_value())

    # No pretty printer has been found
    return None


#=------------------------------------------------------------------------------
# Pretty Printer Classes
#=------------------------------------------------------------------------------
class RustStructPrinter:
    def __init__(self, val, omit_first_field, omit_type_name, is_tuple_like):
        self.__val = val
        self.__omit_first_field = omit_first_field
        self.__omit_type_name = omit_type_name
        self.__is_tuple_like = is_tuple_like

    def to_string(self):
        if self.__omit_type_name:
            return None
        return self.__val.type.get_unqualified_type_name()

    def children(self):
        cs = []
        wrapped_value = self.__val.get_wrapped_value()

        for field in self.__val.type.get_fields():
            field_value = wrapped_value[field.name]
            if self.__is_tuple_like:
                cs.append(("", field_value))
            else:
                cs.append((field.name, field_value))

        if self.__omit_first_field:
            cs = cs[1:]

        return cs

    def display_hint(self):
        if self.__is_tuple_like:
            return "array"
        else:
            return ""


class RustSlicePrinter:
    def __init__(self, val):
        self.__val = val

    def display_hint(self):
        return "array"

    def to_string(self):
        (length, data_ptr) = rustpp.extract_length_and_ptr_from_slice(self.__val)
        return (self.__val.type.get_unqualified_type_name() +
                ("(len: %i)" % length))

    def children(self):
        (length, data_ptr) = rustpp.extract_length_and_ptr_from_slice(self.__val)
        assert data_ptr.type.get_dwarf_type_kind() == rustpp.DWARF_TYPE_CODE_PTR
        raw_ptr = data_ptr.get_wrapped_value()

        for index in xrange(0, length):
            yield (str(index), (raw_ptr + index).dereference())


class RustStringSlicePrinter:
    def __init__(self, val):
        self.__val = val

    def to_string(self):
        (length, data_ptr) = rustpp.extract_length_and_ptr_from_slice(self.__val)
        raw_ptr = data_ptr.get_wrapped_value()
        return '"%s"' % raw_ptr.string(encoding="utf-8", length=length)


class RustStdVecPrinter:
    def __init__(self, val):
        self.__val = val

    def display_hint(self):
        return "array"

    def to_string(self):
        (length, data_ptr, cap) = rustpp.extract_length_ptr_and_cap_from_std_vec(self.__val)
        return (self.__val.type.get_unqualified_type_name() +
                ("(len: %i, cap: %i)" % (length, cap)))

    def children(self):
        (length, data_ptr, cap) = rustpp.extract_length_ptr_and_cap_from_std_vec(self.__val)
        gdb_ptr = data_ptr.get_wrapped_value()
        for index in xrange(0, length):
            yield (str(index), (gdb_ptr + index).dereference())


class RustStdStringPrinter:
    def __init__(self, val):
        self.__val = val

    def to_string(self):
        vec = self.__val.get_child_at_index(0)
        (length, data_ptr, cap) = rustpp.extract_length_ptr_and_cap_from_std_vec(vec)
        return '"%s"' % data_ptr.get_wrapped_value().string(encoding="utf-8",
                                                            length=length)


class RustCStyleVariantPrinter:
    def __init__(self, val):
        assert val.type.get_dwarf_type_kind() == rustpp.DWARF_TYPE_CODE_ENUM
        self.__val = val

    def to_string(self):
        return str(self.__val.get_wrapped_value())


class IdentityPrinter:
    def __init__(self, string):
        self.string = string

    def to_string(self):
        return self.string


def get_field_at_index(gdb_val, index):
    i = 0
    for field in gdb_val.type.fields():
        if i == index:
            return field
        i += 1
    return None