[issue26493] Bad formatting in WinError 193 when using subprocess.check_call

[Eryk Sun]

Eryk Sun added the comment:

When Python creates an exception generically from a Windows error code, it calls WinAPI FormatMessage with the flag FORMAT_MESSAGE_IGNORE_INSERTS. The reason for this is explained in a blog post written by Raymond Chen[1]: "when you are not in control of the message, you had better pass the FORMAT_MESSAGE_IGNORE_INSERTS flag."

[1]: https://blogs.msdn.microsoft.com/oldnewthing/20071128-00/?p=24353

Some extension modules in the code base get this wrong. For example, ctypes.FormatError() doesn't use FORMAT_MESSAGE_IGNORE_INSERTS, so it fails to get the system error message for ERROR_BAD_EXE_FORMAT (193) and just returns its default string "<no description>":

    >>> ctypes.FormatError(193)
    '<no description>'

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components: +Windows
nosy: +eryksun, paul.moore, steve.dower, tim.golden, zach.ware
type:  -> behavior

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue26493>
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