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Merge pull request #91280 from Mitten-O/topic/gdb-pretty-printer
Add a GDB pretty printer to aid in debugging
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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 | ||
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import gdb | ||
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# Printer for Godot StringName variables. | ||
class GodotStringNamePrinter: | ||
def __init__(self, value): | ||
self.value = value | ||
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def to_string(self): | ||
return self.value["_data"]["name"]["_cowdata"]["_ptr"] | ||
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# Hint that the object is string-like. | ||
def display_hint(self): | ||
return "string" | ||
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# Printer for Godot String variables. | ||
class GodotStringPrinter: | ||
def __init__(self, value): | ||
self.value = value | ||
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def to_string(self): | ||
return self.value["_cowdata"]["_ptr"] | ||
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# Hint that the object is string-like. | ||
def display_hint(self): | ||
return "string" | ||
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# Printer for Godot Vector variables. | ||
class GodotVectorPrinter: | ||
def __init__(self, value): | ||
self.value = value | ||
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# 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 | ||
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# 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()) | ||
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# 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() | ||
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def to_string(self): | ||
return "%s [%d]" % (self.value.type.name, self.get_size()) | ||
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# Hint that the object is array-like. | ||
def display_hint(self): | ||
return "array" | ||
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VECTOR_REGEX = re.compile("^Vector<.*$") | ||
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# 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 | ||
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# 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) |