struct.calcsize returns strange size

[igormikushkin]

BPO	7189
Nosy	@mdickinson

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2009-10-23.10:37:08.394>
created_at = <Date 2009-10-23.10:24:27.255>
labels = ['invalid', 'type-bug', 'library']
title = 'struct.calcsize returns strange size'
updated_at = <Date 2009-10-23.10:37:08.370>
user = 'https://bugs.python.org/igormikushkin'

bugs.python.org fields:

activity = <Date 2009-10-23.10:37:08.370>
actor = 'mark.dickinson'
assignee = 'none'
closed = True
closed_date = <Date 2009-10-23.10:37:08.394>
closer = 'mark.dickinson'
components = ['Library (Lib)']
creation = <Date 2009-10-23.10:24:27.255>
creator = 'igor.mikushkin'
dependencies = []
files = []
hgrepos = []
issue_num = 7189
keywords = []
message_count = 2.0
messages = ['94379', '94380']
nosy_count = 2.0
nosy_names = ['mark.dickinson', 'igor.mikushkin']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = None
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue7189'
versions = ['Python 2.6']

[igormikushkin]

I think in second case struct size should be 53.

In [31]: struct.calcsize('ihhi35scc')
Out[31]: 49

In [32]: struct.calcsize('ihhi35scci')
Out[32]: 56

[mdickinson]

I think the calcsize result is correct here. With the native struct
format, padding is included in the struct.

In the second case, there are three bytes of padding after the 'cc' and
before the 'i'. This keeps the 'i' aligned on a 4-byte boundary. If you
look at the results of struct.pack, you can see the padding explicitly:

Python 2.6.1 (r261:67515, Jul  7 2009, 23:51:51) 
[GCC 4.2.1 (Apple Inc. build 5646)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import struct
>>> struct.pack('ihhi35scci', 123456789, 10000, 10000, 321456789, 
"abcdefghijklmnopqrstuvwxyz123456789", '+', '*', 231456789)
"\x15\xcd[\x07\x10'\x10'\x95\n)\x13abcdefghijklmnopqrstuvwxyz123456789+*\x
00\x00\x00\x15\xc0\xcb\r"