# Buggy code
def string_references(self, minimum_length=2, vex_only=False):
    """
    All of the constant string references used by this function.

    :param minimum_length:  The minimum length of strings to find (default is 1)
    :param vex_only:        Only analyze VEX IR, don't interpret the entry state to detect additional constants.
    :return:                A list of tuples of (address, string) where is address is the location of the string in
                            memory.
    """
    strings = []
    memory = self._project.loader.memory

    # get known instruction addresses and call targets
    # these addresses cannot be string references, but show up frequently in the runtime values
    known_executable_addresses = set()
    for block in self.blocks:
        known_executable_addresses.update(block.instruction_addrs)
    for function in self._function_manager.values():
        known_executable_addresses.update(set(x.addr for x in function.graph.nodes()))

    # loop over all local runtime values and check if the value points to a printable string
    for addr in self.local_runtime_values if not vex_only else self.code_constants:
        if not isinstance(addr, claripy.fp.FPV) and addr in memory:
            # check that the address isn't an pointing to known executable code
            # and that it isn't an indirect pointer to known executable code
            try:
                possible_pointer = memory.unpack_word(addr)
                if (
                    addr not in known_executable_addresses
                    and possible_pointer not in known_executable_addresses
                ):
                    # build string
                    stn = ""
                    offset = 0
                    current_char = memory[addr + offset]
                    while chr(current_char) in string.printable:
                        stn += current_char
                        offset += 1
                        current_char = memory[addr + offset]

                    # check that the string was a null terminated string with minimum length
                    if current_char == "\x00" and len(stn) >= minimum_length:
                        strings.append((addr, stn))
            except KeyError:
                pass
    return strings


# Traceback (TypeError)
Traceback (most recent call last):
File ".\src\gaeInputGeneration.py", line 109, in <module>
for offset, strRef in func.string_references(vex_only=True):
File "C:\Users\lixue\AppData\Local\Programs\Python\Python36\lib\site-packages\angr\knowledge_plugins\functions\function.py", line 301, in string_references
while current_char in string.printable:
TypeError: 'in <string>' requires string as left operand, not int

# Fixed code
def string_references(self, minimum_length=2, vex_only=False):
    """
    All of the constant string references used by this function.

    :param minimum_length:  The minimum length of strings to find (default is 1)
    :param vex_only:        Only analyze VEX IR, don't interpret the entry state to detect additional constants.
    :return:                A list of tuples of (address, string) where is address is the location of the string in
                            memory.
    """
    strings = []
    memory = self._project.loader.memory

    # get known instruction addresses and call targets
    # these addresses cannot be string references, but show up frequently in the runtime values
    known_executable_addresses = set()
    for block in self.blocks:
        known_executable_addresses.update(block.instruction_addrs)
    for function in self._function_manager.values():
        known_executable_addresses.update(set(x.addr for x in function.graph.nodes()))

    # loop over all local runtime values and check if the value points to a printable string
    for addr in self.local_runtime_values if not vex_only else self.code_constants:
        if not isinstance(addr, claripy.fp.FPV) and addr in memory:
            # check that the address isn't an pointing to known executable code
            # and that it isn't an indirect pointer to known executable code
            try:
                possible_pointer = memory.unpack_word(addr)
                if (
                    addr not in known_executable_addresses
                    and possible_pointer not in known_executable_addresses
                ):
                    # build string
                    stn = ""
                    offset = 0
                    current_char = chr(memory[addr + offset])
                    while current_char in string.printable:
                        stn += current_char
                        offset += 1
                        current_char = chr(memory[addr + offset])

                    # check that the string was a null terminated string with minimum length
                    if current_char == "\x00" and len(stn) >= minimum_length:
                        strings.append((addr, stn))
            except KeyError:
                pass
    return strings