Lib/test/test_bigaddrspace.py

"""
These tests are meant to exercise that requests to create objects bigger
than what the address space allows are properly met with an OverflowError
(rather than crash weirdly).

Primarily, this means 32-bit builds with at least 2 GiB of available memory.
You need to pass the -M option to regrtest (e.g. "-M 2.1G") for tests to
be enabled.
"""

from test import support
from test.support import bigaddrspacetest, MAX_Py_ssize_t

import unittest
import operator
import sys


class BytesTest(unittest.TestCase):

    @bigaddrspacetest
    def test_concat(self):
        # Allocate a bytestring that's near the maximum size allowed by
        # the address space, and then try to build a new, larger one through
        # concatenation.
        try:
            x = b"x" * (MAX_Py_ssize_t - 128)
            self.assertRaises(OverflowError, operator.add, x, b"x" * 128)
        finally:
            x = None

    @bigaddrspacetest
    def test_optimized_concat(self):
        try:
            x = b"x" * (MAX_Py_ssize_t - 128)

            with self.assertRaises(OverflowError) as cm:
                # this statement used a fast path in ceval.c
                x = x + b"x" * 128

            with self.assertRaises(OverflowError) as cm:
                # this statement used a fast path in ceval.c
                x +=  b"x" * 128
        finally:
            x = None

    @bigaddrspacetest
    def test_repeat(self):
        try:
            x = b"x" * (MAX_Py_ssize_t - 128)
            self.assertRaises(OverflowError, operator.mul, x, 128)
        finally:
            x = None


class StrTest(unittest.TestCase):

    unicodesize = 4

    @bigaddrspacetest
    def test_concat(self):
        try:
            # Create a string that would fill almost the address space
            x = "x" * int(MAX_Py_ssize_t // (1.1 * self.unicodesize))
            # Unicode objects trigger MemoryError in case an operation that's
            # going to cause a size overflow is executed
            self.assertRaises(MemoryError, operator.add, x, x)
        finally:
            x = None

    @bigaddrspacetest
    def test_optimized_concat(self):
        try:
            x = "x" * int(MAX_Py_ssize_t // (1.1 * self.unicodesize))

            with self.assertRaises(MemoryError) as cm:
                # this statement uses a fast path in ceval.c
                x = x + x

            with self.assertRaises(MemoryError) as cm:
                # this statement uses a fast path in ceval.c
                x +=  x
        finally:
            x = None

    @bigaddrspacetest
    def test_repeat(self):
        try:
            x = "x" * int(MAX_Py_ssize_t // (1.1 * self.unicodesize))
            self.assertRaises(MemoryError, operator.mul, x, 2)
        finally:
            x = None


if __name__ == '__main__':
    if len(sys.argv) > 1:
        support.set_memlimit(sys.argv[1])
    unittest.main()