in window7  (using python 3.4.3,3.5.2) following script crashes

import os
os.spawnl( os.P_NOWAIT, 'C:/Tcl/bin/tclsh.exe' )"

Note: similar issue is already exist https://bugs.python.org/issue8036

small correction (removed " )

import os
os.spawnl( os.P_NOWAIT, 'C:/Tcl/bin/tclsh.exe' )

Just to make sure: a crash means that the Python process is killed and you get a popup or something like that?

Can you please try to run the script on Python 3.6 using:

python.exe -X faulthandler script.py

It should display the Windows error code at least.

spawnl is implemented by calling _spawnv [1], which is documented to invoke the invalid parameter handler if argv points to a NULL pointer. It wants the program name, or whatever, as long as argv[0] isn't NULL or an empty string, e.g. `os.spawnl(os.P_NOWAIT, 'C:/Tcl/bin/tclsh.exe', 'tclsh')`. 

The invalid parameter handler should be disabled (_Py_BEGIN_SUPPRESS_IPH) when calling _spawnv[e], which in this case would lead to an EINVAL OSError instead of crashing the process. 

For example:

    import os, sys
    from ctypes import *

    ucrt = CDLL('ucrtbase')

    @CFUNCTYPE(None, c_wchar_p, c_wchar_p, c_wchar_p, c_int, c_void_p)
    def iph(*args):
        pass

    ucrt._set_thread_local_invalid_parameter_handler(iph)

    >>> os.spawnl(os.P_NOWAIT, sys.executable)
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "C:\Program Files\Python35\lib\os.py", line 977, in spawnl
        return spawnv(mode, file, args)
    OSError: [Errno 22] Invalid argument

Also, in this case a descriptive ValueError would be friendlier, given an empty argv or argv[0] that's an empty string -- at least on Windows.

[1]: https://msdn.microsoft.com/en-us/library/7zt1y878.aspx

I like the idea of using _Py_BEGIN_SUPPRESS_IPH, but also the idea of
implementing most obvious checks on arguments. Sadly, I don't have
access to Windows yet to write such patch. Eryk, if you write such
patch, I would be happy to review it ;-) Especially if it includes
unit tests :-D

Looks like a few functions in os module need this. os_execve_impl also doesn't release the GIL at any point, but I don't see why it shouldn't.

I'll try and get to this over the weekend if nobody else comes up with a patch first.

New changeset 02f416441def by Steve Dower in branch '3.5':
Issue #28732: Fix crash in os.spawnv() with no elements in args
https://hg.python.org/cpython/rev/02f416441def

A ValueError should also be raised when argv[0] is an empty string.

New changeset 1a9e4b465497 by Steve Dower in branch '3.6':
Issue #28732: Raise ValueError when os.spawn*() is passed an empty tuple of arguments
https://hg.python.org/cpython/rev/1a9e4b465497

New changeset 75824899f0dd by Steve Dower in branch 'default':
Issue #28732: Raise ValueError when os.spawn*() is passed an empty tuple of arguments
https://hg.python.org/cpython/rev/75824899f0dd

New changeset e076ace7b0ff by Steve Dower in branch '3.5':
Issue #28732: Raise ValueError when argv[0] is empty.
https://hg.python.org/cpython/rev/e076ace7b0ff

New changeset af78b33704af by Steve Dower in branch '3.6':
Issue #28732: Raise ValueError when argv[0] is empty
https://hg.python.org/cpython/rev/af78b33704af

New changeset fc6f757e53de by Steve Dower in branch 'default':
Issue #28732: Raise ValueError when argv[0] is empty
https://hg.python.org/cpython/rev/fc6f757e53de

> ValueError should also be raised when argv[0] is an empty string.

Added that too.

Python 3.5 is missing the tests for these functions completely, so I only added those to 3.6 and later. Also the original issue was already resolved in 3.6, but I tidied up a few other functions that were missing proper handling.

New changeset 2e1fb851dfb4 by Steve Dower in branch '3.6':
Issue #28732: Adds new errors to spawnv emulation for platforms that only have fork and execv
https://hg.python.org/cpython/rev/2e1fb851dfb4

New changeset ac6de11fbd50 by Steve Dower in branch 'default':
Issue #28732: Adds new errors to spawnv emulation for platforms that only have fork and execv
https://hg.python.org/cpython/rev/ac6de11fbd50

Buildbots seem to be happy now so I'm closing the issue.

Feel free to reopen if anyone spots anything in commit review.