subprocess.Popen inheriting

[Gabriel Genellina]

En Wed, 17 Dec 2008 22:46:32 -0200, Aaron Brady <castironpi at gmail.com>  
escribió:
> On Dec 17, 5:05 pm, "Gabriel Genellina" <gagsl-... at yahoo.com.ar>
> wrote:
>> En Wed, 17 Dec 2008 12:21:38 -0200, Jeremy Sanders  
>> <jeremy+complangpyt... at jeremysanders.net> escribió:
>>
>> > It would be nice if Python created pipes that are properly  
>> inheritable by
>> > default by child processes, as they're mostly used for IPC.
>>
>> I'd say it is a bug in os.pipe implementation; they should be  
>> inheritable  
>> by default, as in posix (after all, the code is in "posixmodule.c").
>
> The code looks like this:
>
> 	ok = CreatePipe(&read, &write, NULL, 0);
> 	Py_END_ALLOW_THREADS
> 	if (!ok)
> 		return win32_error("CreatePipe", NULL);
> 	read_fd = _open_osfhandle((Py_intptr_t)read, 0);
> 	write_fd = _open_osfhandle((Py_intptr_t)write, 1);
>
> 'If lpPipeAttributes is NULL, the handle cannot be inherited.'  You
> could populate a 'SECURITY_ATTRIBUTES' structure, or call
> DuplicateHandle on both of them.
>
> A patch would look like this:
>
> SECURITY_ATTRIBUTES sattribs;
> sattribs.nLength = sizeof(sattribs);
> sattribs.lpSecurityDescriptor = NULL;
> sattribs.bInheritHandle = TRUE;
> ok = CreatePipe(&read, &write, &sattribs, 0);

Yes, that's exactly how os.popen does it (in posixmodule.c)

> This still doesn't answer whether the file descriptor return by
> '_open_osfhandle' can be inherited too.

It doesn't matter. The OS only cares about file handles, not C RTL  
structures.

-- 
Gabriel Genellina