[New-bugs-announce] [issue15573] Support unknown formats in memoryview comparisons

[Stefan Krah]

New submission from Stefan Krah:

Continuing the discussion from #13072. I hit a snag here:

Determining in full generality whether two format strings describe
identical items is pretty complicated, see also #3132.


I'm attaching a best effort fmtcmp() function that should do the
following:

  - recognize byte order specifiers at the start of the string.

  - recognize if an explicitly specified byte order happens to
    match the native byte order.

It won't catch:

  - byte order specifiers anywhere in the string.

  - C types that happen to be identical ('I', 'L' on a 32-bit
    platform). I'm also not sure if that is desirable in the
    first place.

  - ???


So fmtcmp() will return false negatives (not equal), but should be
correct for *most* format strings that are actually in use.


Mark, Meador: You did a lot of work on the struct module and of
course on issue #3132. Does this look like a reasonable compromise?
Did I miss obvious cases (see attachment)?

----------
assignee: skrah
components: Interpreter Core
files: format.c
messages: 167618
nosy: Arfrever, georg.brandl, haypo, mark.dickinson, meador.inge, ncoghlan, pitrou, python-dev, skrah
priority: release blocker
severity: normal
stage: needs patch
status: open
title: Support unknown formats in memoryview comparisons
type: behavior
versions: Python 3.3
Added file: http://bugs.python.org/file26720/format.c

_______________________________________
Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue15573>
_______________________________________