[New-bugs-announce] [issue24747] ctypes silently truncates ints larger than C int

[Petr Viktorin]

New submission from Petr Viktorin:

A Python int larger than a C int but smaller than a C long is silently truncated to int when passed to a ctypes function without C type information attached.

Ints longer than C long fail with an OverflowError; I believe the same should happen for numbers that don't fit in a C int.


Reproducer (for 64-bit systems):

    from ctypes import cdll, ArgumentError
    libc = cdll.LoadLibrary("libc.so.6")


    # Silently truncated
    libc.printf(b"%x\n", 0x1234567890)

    try:
        # OverflowError raised
        libc.printf(b"%x\n", 2 ** 64)
    except ArgumentError as e:
        print(e)


see callproc.c, function ConvParam, after the PyLong_Check.

----------
components: ctypes
messages: 247565
nosy: encukou
priority: normal
severity: normal
status: open
title: ctypes silently truncates ints larger than C int
versions: Python 2.7, Python 3.4, Python 3.5, Python 3.6

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue24747>
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