Gregory P. Smith
Fri Dec 14 10:14:04 CET 2012Previous message:
[Python-Dev] cpython: Using 'long double' to force this structure to be worst case aligned is no
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[Python-Dev] cpython: Using 'long double' to force this structure to be worst case aligned is no
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Yes, see the followup. My comments before were all misinterpreting size_t. Same result on x86_64 linux. On a 64-bit platform the 24 byte structure now occupies 24 bytes instead of being padded to 32. Nice. On a 32-bit platform it should remain 16 bytes. The PyGC_Head union structure is NOT part of the ABI laid out in
http://www.python.org/dev/peps/pep-0384/
and is accurately excluded from the .h file when Py_LIMITED_API is defined so changing this in 3.4 should not be a problem. This structure occupies the space gc tracked PyObject* pointers. -gps On Fri, Dec 14, 2012 at 12:42 AM, Mark Dickinson <
> wrote: > On Fri, Dec 14, 2012 at 7:27 AM, Gregory P. Smith <
> wrote: > > So changing the definition of the dummy side of the union makes zero > > difference to already compiled code as it (a) doesn't change the > structure's > > size and (b) all existing implementations already align these on an 8 > byte > > boundary. >> It looks to me as though the struct size *is* changed, at least on > some platforms. Before this commit, I get (OS X 10.6, 64-bit > non-debug build): >> Python 3.4.0a0 (default:b4c383f31881+, Dec 14 2012, 08:30:39) > [GCC 4.2.1 (Apple Inc. build 5664)] on darwin > Type "help", "copyright", "credits" or "license" for more information. > >>> class A(object): pass > ... > >>> a = A() > >>> import sys > >>> sys.getsizeof(a) > 64 >>> After it: >> Python 3.4.0a0 (default:76bc92fb90c1+, Dec 14 2012, 08:33:48) > [GCC 4.2.1 (Apple Inc. build 5664)] on darwin > Type "help", "copyright", "credits" or "license" for more information. > >>> class A(object): pass > ... > >>> a = A() > >>> import sys > >>> sys.getsizeof(a) > 56 >> -- > Mark >-------------- next part -------------- An HTML attachment was scrubbed... URL: <
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[Python-Dev] cpython: Using 'long double' to force this structure to be worst case aligned is no
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