GDB pretty printers for Odin types

odin-gdb-pretty-printers.py

import gdb
import re

# Set it to true if you're using Microsoft's vscode plugin for c/c++.
# This works around the fact that it doesn't handle "map" display hints properly.
enable_msft_workarounds = False

class OdinAnyPrinter(gdb.ValuePrinter):
	"Pretty print Odin any."

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

	def display_hint(self):
		if enable_msft_workarounds:
			return None
		return "map"

	def to_string(self):
		return int(self.__val['id'])

	def children(self):
		yield ('id', self.__val['id'])
		yield ('data', self.__val['data'])

def any_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if val.type.tag != "any":
		return None
	return OdinAnyPrinter(val)

gdb.pretty_printers.append(any_lookup_function)

class OdinTypeidPrinter(gdb.ValuePrinter):
	"Pretty print Odin typeids."

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

	def display_hint(self):
		if enable_msft_workarounds:
			return None
		return "map"

	def to_string(self):
		return int(self.__val)

	def children(self):
		id         = int(self.__val)
		mask       = (1 << (8 * self.__val.type.sizeof - 8)) - 1
		n          = (id & mask)
		sym        = gdb.lookup_static_symbol("type_table")
		type_table = sym.value()
		yield ("type_info", (type_table['data'] + (id & mask)).dereference().dereference())

def typeid_lookup_function(val):
	if val.type.name != "typeid":
		return None
	return OdinTypeidPrinter(val)

gdb.pretty_printers.append(typeid_lookup_function)

class OdinRunePrinter(gdb.ValuePrinter):
	"Pretty print Odin runes."

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

	def to_string(self):
		return f"{int(self.__val)} '{str(chr(int(self.__val)))}'"

def rune_lookup_function(val):
	if val.type.name != "rune":
		return None
	return OdinRunePrinter(val)

gdb.pretty_printers.append(rune_lookup_function)

class OdinStringPrinter(gdb.ValuePrinter):
	"Pretty print Odin strings."

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

	def display_hint(self):
		return "string"

	def to_string(self):
		return self.__val["data"].string("utf-8", "ignore", int(self.__val["len"]))

def string_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if val.type.tag != "string":
		return None
	return OdinStringPrinter(val)

gdb.pretty_printers.append(string_lookup_function)

class OdinUnionPrinter(gdb.ValuePrinter):
	"Pretty print Odin unions."

	def __init__(self, val):
		self.__val = val
		self.__tag = int(val["tag"])

	def display_hint(self):
		if enable_msft_workarounds:
			return None
		return "map"

	def to_string(self):
		if self.__tag == 0:
			return "<nil>"
		return self.__val[f"v{self.__tag}"]

	def children(self):
		if self.__tag != 0:
			yield ("value", self.__val[f"v{self.__tag}"])

def union_lookup_function(val):
	if val.type.code != gdb.TYPE_CODE_UNION:
		return None
	has_tag = False
	for f in val.type.fields():
		if f.name == 'tag':
			has_tag = True
		elif not f.name.startswith('v'):
			return None
	if not has_tag:
		return None
	return OdinUnionPrinter(val)

gdb.pretty_printers.append(union_lookup_function)


class OdinSlicePrinter(gdb.ValuePrinter):
	"Pretty print Odin slices."

	def __init__(self, val):
		self.__val  = val
		self.__len  = int(self.__val["len"])
		self.__data = self.__val["data"]

	def display_hint(self):
		return "array"

	def to_string(self):
		name = str(self.__val.type)
		name = name[len("struct "):]
		return f"{name} len = {self.__len}, data = 0x{int(self.__data):x}"

	def child(self, i):
		if i > self.__len:
			return None
		return (self.__data + i).dereference()

	def num_children(self):
		return self.__len

	def children(self):
		if self.__data.type.target().sizeof == 0:
			return
		for i in range(int(self.__len)):
			yield (f"[{i}]", (self.__data + i).dereference())

def slice_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if not val.type.tag.startswith("[]"):
		return None
	return OdinSlicePrinter(val)

gdb.pretty_printers.append(slice_lookup_function)


class OdinSoaSlicePrinter(gdb.ValuePrinter):
	"Pretty print Odin #soa slices."

	def __init__(self, val):
		self.__val = val
		self.__len = int(self.__val["__$len"])

	def display_hint(self):
		if enable_msft_workarounds:
			return None
		return "map"

	def to_string(self):
		name = str(self.__val.type)
		name = name[len("struct "):]
		return f"{name} len = {self.__len}"

	def num_children(self):
		return len(self.__val.type.fields())

	def children(self):
		yield ("__$len", self.__len)
		for field in self.__val.type.fields():
			if field.name == "__$len":
				continue
			yield (field.name, self.__val[field.name].cast(field.type.target().array(self.__len - 1).pointer()).dereference())

def soa_slice_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if not val.type.tag.startswith("#soa[]"):
		return None
	return OdinSoaSlicePrinter(val)

gdb.pretty_printers.append(soa_slice_lookup_function)

class OdinDynamicArrayPrinter(gdb.ValuePrinter):
	"Pretty print Odin dynamic arrays."

	def __init__(self, val):
		self.__val  = val
		self.__len  = int(self.__val["len"])
		self.__cap  = int(self.__val["cap"])
		self.__data = self.__val["data"]

	def display_hint(self):
		if enable_msft_workarounds:
			return None
		return "map"

	def to_string(self):
		name = str(self.__val.type)
		name = name[len("struct "):]
		return f"{name} len = {self.__len}, cap = {self.__cap}"

	def num_children(self):
		return 4

	def children(self):
		yield ("data", self.__data.cast(self.__data.type.target().array(self.__len - 1).pointer()).dereference())
		yield ("len", self.__len)
		yield ("cap", self.__cap)
		yield ("allocator", self.__val["allocator"])

def soa_dynamic_array_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if not val.type.tag.startswith("[dynamic]"):
		return None
	return OdinDynamicArrayPrinter(val)

gdb.pretty_printers.append(soa_dynamic_array_lookup_function)

class OdinSoaDynamicArrayPrinter(gdb.ValuePrinter):
	"Pretty print Odin #soa dynamic arrays."

	def __init__(self, val):
		self.__val = val
		self.__len = int(self.__val["__$len"])
		self.__cap = int(self.__val["__$cap"])

	def display_hint(self):
		if enable_msft_workarounds:
			return None
		return "map"

	def to_string(self):
		name = str(self.__val.type)
		name = name[len("struct "):]
		return f"{name} len = {self.__len}, cap = {self.__cap}"

	def num_children(self):
		return len(self.__val.type.fields())

	def children(self):
		for field in self.__val.type.fields():
			if field.name == "__$len" or field.name == "__$cap" or field.name == "allocator":
				continue
			yield (field.name, self.__val[field.name].cast(field.type.target().array(self.__len - 1).pointer()).dereference())

		yield ("__$len", self.__len)
		yield ("__$cap", self.__cap)
		yield ("allocator", self.__val["allocator"])

def soa_soa_dynamic_array_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if not val.type.tag.startswith("#soa[dynamic]"):
		return None
	return OdinSoaDynamicArrayPrinter(val)

gdb.pretty_printers.append(soa_soa_dynamic_array_lookup_function)

class OdinMapPrinter(gdb.ValuePrinter):
	"Pretty print Odin maps."

	def __init__(self, val):
		self.__val       = val
		self.__len       = val["len"]
		self.__base_addr = int(val["data"].dereference().address) & ~63

		cap_log2   = int(val["data"].dereference().address) & 63
		self.__cap = 0 if cap_log2 <= 0 else 1 << cap_log2

		self.__key_type      = val["data"]["key"].type
		self.__key_cell_type = val["data"]["key_cell"].type
		self.__key_base_addr = self.__base_addr

		self.__value_type      = val["data"]["value"].type
		self.__value_cell_type = val["data"]["value_cell"].type
		self.__value_base_addr = self.__key_base_addr + self.map_cell_offset(self.__key_type, self.__key_cell_type, self.__cap)

		self.__hash_type      = val["data"]["hash"].type
		self.__tombstone_mask = 1 << (self.__hash_type.sizeof * 8 - 1)
		hash_addr             = self.__value_base_addr + self.map_cell_offset(self.__value_type, self.__value_cell_type, self.__cap)
		self.__hashes         = gdb.Value(hash_addr).cast(self.__hash_type.pointer())

	def display_hint(self):
		if self.__value_type.sizeof == 0:
			return "array"
		if enable_msft_workarounds:
			return None
		return "map"

	def num_children(self):
		return self.__len

	def children(self):
		for i in range(self.__cap):
			hash = (self.__hashes + i).dereference()
			if hash == 0 or (hash & self.__tombstone_mask) != 0:
				continue

			key_ptr = self.__key_base_addr + self.map_cell_offset(self.__key_type, self.__key_cell_type, i)
			key     = gdb.Value(key_ptr).cast(self.__key_type.pointer()).dereference()
			if self.__value_type.sizeof == 0:
				yield (f"{i}", key)
			else:
				value_ptr = self.__value_base_addr + self.map_cell_offset(self.__value_type, self.__value_cell_type, i)
				value     = gdb.Value(value_ptr).cast(self.__value_type.pointer()).dereference()
				yield (f"{key}", value)

	def map_cell_offset(self, elem_type, elem_cell_type, index):
		if elem_type.sizeof == 0:
			return 0
		elems_per_cell = elem_cell_type.sizeof // elem_type.sizeof
		cell_index     = index // elems_per_cell
		data_index     = index % elems_per_cell
		return (cell_index * elem_cell_type.sizeof) + (data_index * elem_type.sizeof)

def map_lookup_function(val):
	if val.type.tag is None:
		return None
	if val.type.code != gdb.TYPE_CODE_STRUCT:
		return None
	if not val.type.tag.startswith("map["):
		return None
	return OdinMapPrinter(val)

gdb.pretty_printers.append(map_lookup_function)

Hi, just want to say thank you so much for this! I had a hard time following the implementation of map so the fact you have a working pretty printer right here is so useful to me.

just a small comment for anyone interested: gdb.ValuePrinter is only available starting with GDB 14 (see December 3rd, 2023 announcement). GDB on my WSL Debian installation is stuck at version 13 (ugh)- fortunately there's a workaround from GCC's own libstdcxx printers:

if hasattr(gdb, 'ValuePrinter'):
    printer_base = gdb.ValuePrinter
else:
    printer_base = object

Then we can just inherit from printer_base instead of gdb.ValuePrinter.