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#!/usr/bin/env python3
# Load this file to your GDB session to enable pretty-printing
# of some Godot C++ types.
# GDB command: source misc/scripts/godot_gdb_pretty_print.py
#
# To load these automatically in Visual Studio Code,
# add the source command to the setupCommands of your configuration
# in launch.json.
# "setupCommands": [
# ...
# {
# "description": "Load custom pretty-printers for Godot types.",
# "text": "source ${workspaceRoot}/misc/scripts/godot_gdb_pretty_print.py"
# }
# ]
# Other UI:s that use GDB under the hood are likely to have their own ways to achieve this.
#
# To debug this script it's easiest to use the interactive python from a command-line
# GDB session. Stop at a breakpoint, then use
# python-interactive to enter the python shell and
# acquire a Value object using gdb.selected_frame().read_var("variable name").
# From there you can figure out how to print it nicely.
import re
import gdb
# Printer for Godot StringName variables.
class GodotStringNamePrinter:
def __init__(self, value):
self.value = value
def to_string(self):
return self.value["_data"]["name"]["_cowdata"]["_ptr"]
# Hint that the object is string-like.
def display_hint(self):
return "string"
# Printer for Godot String variables.
class GodotStringPrinter:
def __init__(self, value):
self.value = value
def to_string(self):
return self.value["_cowdata"]["_ptr"]
# Hint that the object is string-like.
def display_hint(self):
return "string"
# Printer for Godot Vector variables.
class GodotVectorPrinter:
def __init__(self, value):
self.value = value
# The COW (Copy On Write) object does a bunch of pointer arithmetic to access
# its members.
# The offsets are constants on the C++ side, optimized out, so not accessible to us.
# I'll just hard code the observed values and hope they are the same forever.
# See core/templates/cowdata.h
SIZE_OFFSET = 8
DATA_OFFSET = 16
# Figures out the number of elements in the vector.
def get_size(self):
cowdata = self.value["_cowdata"]
if cowdata["_ptr"] == 0:
return 0
else:
# The ptr member of cowdata does not point to the beginning of the
# cowdata. It points to the beginning of the data section of the cowdata.
# To get to the length section, we must back up to the beginning of the struct,
# then move back forward to the size.
# cf. CowData::_get_size
ptr = cowdata["_ptr"].cast(gdb.lookup_type("uint8_t").pointer())
return int((ptr - self.DATA_OFFSET + self.SIZE_OFFSET).dereference())
# Lists children of the value, in this case the vector's items.
def children(self):
# Return nothing if ptr is null.
ptr = self.value["_cowdata"]["_ptr"]
if ptr == 0:
return
# Yield the items one by one.
for i in range(self.get_size()):
yield str(i), (ptr + i).dereference()
def to_string(self):
return "%s [%d]" % (self.value.type.name, self.get_size())
# Hint that the object is array-like.
def display_hint(self):
return "array"
VECTOR_REGEX = re.compile("^Vector<.*$")
# Tries to find a pretty printer for a debugger value.
def lookup_pretty_printer(value):
if value.type.name == "StringName":
return GodotStringNamePrinter(value)
if value.type.name == "String":
return GodotStringPrinter(value)
if value.type.name and VECTOR_REGEX.match(value.type.name):
return GodotVectorPrinter(value)
return None
# Register our printer lookup function.
# The first parameter could be used to limit the scope of the printer
# to a specific object file, but that is unnecessary for us.
gdb.printing.register_pretty_printer(None, lookup_pretty_printer)
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