solidity/test/formal/checked_uint_add.py

41 lines
865 B
Python

from opcodes import GT, ADD
from rule import Rule
from util import BVUnsignedMax, BVUnsignedUpCast
from z3 import BitVec, BVAddNoOverflow, Not
"""
Overflow checked unsigned integer addition.
"""
n_bits = 256
type_bits = 8
while type_bits <= n_bits:
rule = Rule()
# Input vars
X_short = BitVec('X', type_bits)
Y_short = BitVec('Y', type_bits)
# Z3's overflow condition
actual_overflow = Not(BVAddNoOverflow(X_short, Y_short, False))
# cast to full n_bits values
X = BVUnsignedUpCast(X_short, n_bits)
Y = BVUnsignedUpCast(Y_short, n_bits)
sum_ = ADD(X, Y)
# Constants
maxValue = BVUnsignedMax(type_bits, n_bits)
# Overflow check in YulUtilFunction::overflowCheckedIntAddFunction
if type_bits == 256:
overflow_check = GT(X, sum_)
else:
overflow_check = GT(sum_, maxValue)
type_bits += 8
rule.check(overflow_check != 0, actual_overflow)