[Python-Dev] struct.pack inconsistencies between platforms

Sun Feb 26 14:45:52 CET 2012

Sounds reasonable for me. Thanks!
On Sun, Feb 26, 2012 at 3:16 PM, Eli Bendersky <eliben at gmail.com> wrote:
>>> On Sun, Feb 26, 2012 at 15:09, Paul Moore <p.f.moore at gmail.com> wrote:
>>> On 26 February 2012 12:34, Eli Bendersky <eliben at gmail.com> wrote:
>> > On Sun, Feb 26, 2012 at 12:33, pmon mail <pmon.mail at gmail.com> wrote:
>> >> Documentation clearly states that the 'L' is a 4 byte integer.
>> >>
>> >> Is this a bug? I'm I missing something?
>> >>
>> >
>> > By default pack uses native size, not standard size. On a 64-bit
>> machine:
>>>> As the OP points out, the documentation says that the "Standard Size"
>> is 4 bytes (http://docs.python.org/library/struct.html). While
>> "Standard Size" doesn't appear to be defined in the documentation, and
>> the start of the previous section (7.3.2.1. Byte Order, Size, and
>> Alignment) clearly states that C types are represented in native
>> format by default, the documentation could probably do with some
>> clarification.
>>>>> 7.2.3.1 says, shortly after the first table:
>> "
>> Native size and alignment are determined using the C compiler’s sizeofexpression. This is always combined with native byte order.
>> Standard size depends only on the format character; see the table in the *Format
> Characters* <http://docs.python.org/library/struct.html#format-characters>section.
> "
>> To me this appears to be a reasonable definition of what "standard size"
> is.
>> 7.3.2.2 says before the size table:
>> "Format characters have the following meaning; the conversion between C
> and Python values should be obvious given their types. The ‘Standard size’
> column refers to the size of the packed value in bytes when using standard
> size; that is, when the format string starts with one of '<', '>', '!' or
> '='. When using native size, the size of the packed value is
> platform-dependent."
>> Again, taken together with the previous quote, IMHO this defines the
> difference between standard and native sizes clearly. If you feel
> differently, feel free to open an issue suggesting a better explanation.
>> Eli
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