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Author eryksun
Recipients ZackerySpytz, daveb, eryksun, josh.r, paul.moore, steve.dower, tim.golden, vstinner, zach.ware
Date 2019-07-10.23:46:01
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
> OSError: [WinError 87] The parameter is incorrect

This error didn't originate from the C dup() call, since that would be based on errno, like `OSError: [Errno 9] Bad file descriptor`. It must come from _Py_set_inheritable. The only WINAPI call there is SetHandleInformation [1], which is documented to support "console input buffer" and "console screen buffer" handles, though it may be that the documentation is wrong.

Try the following code:

    >>> import os, msvcrt
    >>> msvcrt.get_osfhandle(0)
    >>> os.set_handle_inheritable(msvcrt.get_osfhandle(0), False)

Prior to Windows 8, a console handle is tagged by setting the lower 2 bits (e.g. 3, 7, 11). The system uses this tag to direct calls to special console functions that route requests over the console LPC port. Thus, in the domain of File handles, setting the lower 2 bits is reserved to tag console handles. This should also be true in Windows 8+, even though console handle tagging is no longer used (now they're kernel handles for the ConDrv device). 

The above test will confirm my suspicion, but it looks some time around Windows XP/2003, Microsoft removed the internal [Get|Set]ConsoleHandleInformation functions that used to implement [Get|Set]HandleInformation for console handles, and the people responsible for the change failed to update the docs. Since the internal DuplicateConsoleHandle function wasn't removed, dup() itself still succeeds.

I suggest that _Py_set_inheritable should handle this case. If the call fails with ERROR_INVALID_PARAMETER, and the two tag bits of the handle are set, the handle is possibly (not necessarily) a console handle. In this case, if GetFileType is FILE_TYPE_CHARACTER, then it's a console handle, and the error should be ignored.

Date User Action Args
2019-07-10 23:46:02eryksunsetrecipients: + eryksun, paul.moore, vstinner, tim.golden, zach.ware, steve.dower, josh.r, ZackerySpytz, daveb
2019-07-10 23:46:02eryksunsetmessageid: <>
2019-07-10 23:46:02eryksunlinkissue37549 messages
2019-07-10 23:46:01eryksuncreate