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