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llvm-project/lldb/examples/python/formatter_bytecode.py
Dave Lee 4baab258b8
[lldb] Add Get(Non)SyntheticValue formatter bytecodes (#174839) 
`GetSyntheticValue` in synthetic providers which need to operate on raw
root values, but will often want to use the synthetic value of children,
or nested children.
2026-02-12 10:07:17 -08:00

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"""
Specification, compiler, disassembler, and interpreter
for LLDB dataformatter bytecode.
See https://lldb.llvm.org/resources/formatterbytecode.html for more details.
"""
from __future__ import annotations
# Types
type_String = 1
type_Int = 2
type_UInt = 3
type_Object = 4
type_Type = 5
# Opcodes
opcode = dict()
def define_opcode(n, mnemonic, name):
globals()["op_" + name] = n
if mnemonic:
opcode[mnemonic] = n
opcode[n] = mnemonic
define_opcode(1, "dup", "dup")
define_opcode(2, "drop", "drop")
define_opcode(3, "pick", "pick")
define_opcode(4, "over", "over")
define_opcode(5, "swap", "swap")
define_opcode(6, "rot", "rot")
define_opcode(0x10, "{", "begin")
define_opcode(0x11, "if", "if")
define_opcode(0x12, "ifelse", "ifelse")
define_opcode(0x13, "return", "return")
define_opcode(0x20, None, "lit_uint")
define_opcode(0x21, None, "lit_int")
define_opcode(0x22, None, "lit_string")
define_opcode(0x23, None, "lit_selector")
define_opcode(0x2A, "as_int", "as_int")
define_opcode(0x2B, "as_uint", "as_uint")
define_opcode(0x2C, "is_null", "is_null")
define_opcode(0x30, "+", "plus")
define_opcode(0x31, "-", "minus")
define_opcode(0x32, "*", "mul")
define_opcode(0x33, "/", "div")
define_opcode(0x34, "%", "mod")
define_opcode(0x35, "<<", "shl")
define_opcode(0x36, ">>", "shr")
define_opcode(0x40, "&", "and")
define_opcode(0x41, "|", "or")
define_opcode(0x42, "^", "xor")
define_opcode(0x43, "~", "not")
define_opcode(0x50, "=", "eq")
define_opcode(0x51, "!=", "neq")
define_opcode(0x52, "<", "lt")
define_opcode(0x53, ">", "gt")
define_opcode(0x54, "=<", "le")
define_opcode(0x55, ">=", "ge")
define_opcode(0x60, "call", "call")
# Function signatures
sig_summary = 0
sig_init = 1
sig_get_num_children = 2
sig_get_child_index = 3
sig_get_child_at_index = 4
# Selectors
selector = dict()
def define_selector(n, name):
globals()["sel_" + name] = n
selector["@" + name] = n
selector[n] = "@" + name
define_selector(0, "summary")
define_selector(1, "type_summary")
define_selector(0x10, "get_num_children")
define_selector(0x11, "get_child_at_index")
define_selector(0x12, "get_child_with_name")
define_selector(0x13, "get_child_index")
define_selector(0x15, "get_type")
define_selector(0x16, "get_template_argument_type")
define_selector(0x17, "cast")
define_selector(0x18, "get_synthetic_value")
define_selector(0x19, "get_non_synthetic_value")
define_selector(0x20, "get_value")
define_selector(0x21, "get_value_as_unsigned")
define_selector(0x22, "get_value_as_signed")
define_selector(0x23, "get_value_as_address")
define_selector(0x40, "read_memory_byte")
define_selector(0x41, "read_memory_uint32")
define_selector(0x42, "read_memory_int32")
define_selector(0x43, "read_memory_unsigned")
define_selector(0x44, "read_memory_signed")
define_selector(0x45, "read_memory_address")
define_selector(0x46, "read_memory")
define_selector(0x50, "fmt")
define_selector(0x51, "sprintf")
define_selector(0x52, "strlen")
################################################################################
# Compiler.
################################################################################
def compile(assembler: str) -> bytearray:
"""Compile assembler into bytecode"""
# This is a stack of all in-flight/unterminated blocks.
bytecode = [bytearray()]
def emit(byte):
bytecode[-1].append(byte)
tokens = list(assembler.split(" "))
tokens.reverse()
while tokens:
tok = tokens.pop()
if tok == "":
pass
elif tok == "{":
bytecode.append(bytearray())
elif tok == "}":
block = bytecode.pop()
emit(op_begin)
emit(len(block)) # FIXME: uleb
bytecode[-1].extend(block)
elif tok[0].isdigit():
if tok[-1] == "u":
emit(op_lit_uint)
emit(int(tok[:-1])) # FIXME
else:
emit(op_lit_int)
emit(int(tok)) # FIXME
elif tok[0] == "@":
emit(op_lit_selector)
emit(selector[tok])
elif tok[0] == '"':
s = bytearray()
done = False
chrs = tok[1:]
while not done:
quoted = False
for c in chrs:
if quoted:
s.append(ord(c)) # FIXME
quoted = False
elif c == "\\":
quoted = True
elif c == '"':
done = True
break
# FIXME assert this is last in token
else:
s.append(ord(c))
if not done:
s.append(ord(" "))
chrs = tokens.pop()
emit(op_lit_string)
emit(len(s))
bytecode[-1].extend(s)
else:
emit(opcode[tok])
assert len(bytecode) == 1 # unterminated {
return bytecode[0]
################################################################################
# Disassembler.
################################################################################
def disassemble(bytecode: bytearray) -> (str, int):
"""Disassemble bytecode into (assembler, token starts)"""
asm = ""
all_bytes = list(bytecode)
all_bytes.reverse()
blocks = []
tokens = [0]
def next_byte():
"""Fetch the next byte in the bytecode and keep track of all
in-flight blocks"""
for i in range(len(blocks)):
blocks[i] -= 1
tokens.append(len(asm))
return all_bytes.pop()
while all_bytes:
b = next_byte()
if b == op_begin:
asm += "{"
length = next_byte()
blocks.append(length)
elif b == op_lit_uint:
b = next_byte()
asm += str(b) # FIXME uleb
asm += "u"
elif b == op_lit_int:
b = next_byte()
asm += str(b)
elif b == op_lit_selector:
b = next_byte()
asm += selector[b]
elif b == op_lit_string:
length = next_byte()
s = "'"
while length:
s += chr(next_byte())
length -= 1
asm += '"' + repr(s)[2:]
else:
asm += opcode[b]
while blocks and blocks[-1] == 0:
asm += " }"
blocks.pop()
if all_bytes:
asm += " "
if blocks:
asm += "ERROR"
return asm, tokens
################################################################################
# Interpreter.
################################################################################
def count_fmt_params(fmt: str) -> int:
"""Count the number of parameters in a format string"""
from string import Formatter
f = Formatter()
n = 0
for _, name, _, _ in f.parse(fmt):
if name > n:
n = name
return n
def interpret(bytecode: bytearray, control: list, data: list, tracing: bool = False):
"""Interpret bytecode"""
frame = []
frame.append((0, len(bytecode)))
def trace():
"""print a trace of the execution for debugging purposes"""
def fmt(d):
if isinstance(d, int):
return str(d)
if isinstance(d, str):
return d
return repr(type(d))
pc, end = frame[-1]
asm, tokens = disassemble(bytecode)
print(
"=== frame = {1}, data = {2}, opcode = {0}".format(
opcode[b], frame, [fmt(d) for d in data]
)
)
print(asm)
print(" " * (tokens[pc]) + "^")
def next_byte():
"""Fetch the next byte and update the PC"""
pc, end = frame[-1]
assert pc < len(bytecode)
b = bytecode[pc]
frame[-1] = pc + 1, end
# At the end of a block?
while pc >= end:
frame.pop()
if not frame:
return None
pc, end = frame[-1]
if pc >= end:
return None
b = bytecode[pc]
frame[-1] = pc + 1, end
return b
while frame[-1][0] < len(bytecode):
b = next_byte()
if b == None:
break
if tracing:
trace()
# Data stack manipulation.
if b == op_dup:
data.append(data[-1])
elif b == op_drop:
data.pop()
elif b == op_pick:
data.append(data[data.pop()])
elif b == op_over:
data.append(data[-2])
elif b == op_swap:
x = data.pop()
y = data.pop()
data.append(x)
data.append(y)
elif b == op_rot:
z = data.pop()
y = data.pop()
x = data.pop()
data.append(z)
data.append(x)
data.append(y)
# Control stack manipulation.
elif b == op_begin:
length = next_byte()
pc, end = frame[-1]
control.append((pc, pc + length))
frame[-1] = pc + length, end
elif b == op_if:
if data.pop():
frame.append(control.pop())
elif b == op_ifelse:
if data.pop():
control.pop()
frame.append(control.pop())
else:
frame.append(control.pop())
control.pop()
elif b == op_return:
control.clear()
return data[-1]
# Literals.
elif b == op_lit_uint:
b = next_byte() # FIXME uleb
data.append(int(b))
elif b == op_lit_int:
b = next_byte() # FIXME uleb
data.append(int(b))
elif b == op_lit_selector:
b = next_byte()
data.append(b)
elif b == op_lit_string:
length = next_byte()
s = ""
while length:
s += chr(next_byte())
length -= 1
data.append(s)
elif b == op_as_uint:
pass
elif b == op_as_int:
pass
elif b == op_is_null:
data.append(1 if data.pop() == None else 0)
# Arithmetic, logic, etc.
elif b == op_plus:
data.append(data.pop() + data.pop())
elif b == op_minus:
data.append(-data.pop() + data.pop())
elif b == op_mul:
data.append(data.pop() * data.pop())
elif b == op_div:
y = data.pop()
data.append(data.pop() / y)
elif b == op_mod:
y = data.pop()
data.append(data.pop() % y)
elif b == op_shl:
y = data.pop()
data.append(data.pop() << y)
elif b == op_shr:
y = data.pop()
data.append(data.pop() >> y)
elif b == op_and:
data.append(data.pop() & data.pop())
elif b == op_or:
data.append(data.pop() | data.pop())
elif b == op_xor:
data.append(data.pop() ^ data.pop())
elif b == op_not:
data.append(not data.pop())
elif b == op_eq:
data.append(data.pop() == data.pop())
elif b == op_neq:
data.append(data.pop() != data.pop())
elif b == op_lt:
data.append(data.pop() > data.pop())
elif b == op_gt:
data.append(data.pop() < data.pop())
elif b == op_le:
data.append(data.pop() >= data.pop())
elif b == op_ge:
data.append(data.pop() <= data.pop())
# Function calls.
elif b == op_call:
sel = data.pop()
if sel == sel_summary:
data.append(data.pop().GetSummary())
elif sel == sel_get_num_children:
data.append(data.pop().GetNumChildren())
elif sel == sel_get_child_at_index:
index = data.pop()
valobj = data.pop()
data.append(valobj.GetChildAtIndex(index))
elif sel == sel_get_child_with_name:
name = data.pop()
valobj = data.pop()
data.append(valobj.GetChildMemberWithName(name))
elif sel == sel_get_child_index:
name = data.pop()
valobj = data.pop()
data.append(valobj.GetIndexOfChildWithName(name))
elif sel == sel_get_type:
data.append(data.pop().GetType())
elif sel == sel_get_template_argument_type:
n = data.pop()
valobj = data.pop()
data.append(valobj.GetTemplateArgumentType(n))
elif sel == sel_get_synthetic_value:
data.append(data.pop().GetSyntheticValue())
elif sel == sel_get_non_synthetic_value:
data.append(data.pop().GetNonSyntheticValue())
elif sel == sel_get_value:
data.append(data.pop().GetValue())
elif sel == sel_get_value_as_unsigned:
data.append(data.pop().GetValueAsUnsigned())
elif sel == sel_get_value_as_signed:
data.append(data.pop().GetValueAsSigned())
elif sel == sel_get_value_as_address:
data.append(data.pop().GetValueAsAddress())
elif sel == sel_cast:
sbtype = data.pop()
valobj = data.pop()
data.append(valobj.Cast(sbtype))
elif sel == sel_strlen:
s = data.pop()
data.append(len(s) if s else 0)
elif sel == sel_fmt:
fmt = data.pop()
n = count_fmt_params(fmt)
args = []
for i in range(n):
args.append(data.pop())
data.append(fmt.format(*args))
else:
print("not implemented: " + selector[sel])
assert False
pass
return data[-1]
if __name__ == "__main__":
# Work around the fact that one of the local files is called
# types.py, which breaks some versions of python.
import os, sys
path = os.path.abspath(os.path.dirname(__file__))
sys.path.remove(path)
import argparse
parser = argparse.ArgumentParser(
description="""
Compiler, disassembler, and interpreter for LLDB dataformatter bytecode.
See https://lldb.llvm.org/resources/formatterbytecode.html for more details.
"""
)
parser.add_argument(
"-c", "--compile", type=str, help="compile assembler into bytecode"
)
parser.add_argument("-d", "--disassemble", type=str, help="disassemble bytecode")
parser.add_argument("-t", "--test", action="store_true", help="run unit tests")
args = parser.parse_args()
if args.compile:
print(compile(str(args.compile)).hex())
if args.disassemble:
print(disassemble(bytearray.fromhex(str(args.disassemble))))
############################################################################
# Tests.
############################################################################
if args.test:
import unittest
class TestCompiler(unittest.TestCase):
def test(self):
self.assertEqual(compile("1u dup").hex(), "200101")
self.assertEqual(compile('"1u dup"').hex(), "2206317520647570")
self.assertEqual(compile("16 < { dup } if").hex(), "21105210010111")
self.assertEqual(compile('{ { " } " } }').hex(), "100710052203207d20")
def roundtrip(asm):
self.assertEqual(disassemble(compile(asm))[0], asm)
roundtrip("1u dup")
roundtrip('1u dup "1u dup"')
roundtrip("16 < { dup } if")
roundtrip('{ { " } " } }')
self.assertEqual(interpret(compile("1 1 +"), [], []), 2)
self.assertEqual(interpret(compile("2 1 1 + *"), [], []), 4)
self.assertEqual(
interpret(compile('2 1 > { "yes" } { "no" } ifelse'), [], []), "yes"
)
import sys
sys.argv.pop()
path = os.path.dirname(__file__)
sys.path.remove
unittest.main()
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