[Tcl-bugs] [ tcl-Bugs-419685 ] Problem with [file channels] if std channels not available

[<no...@so...>]

Bugs item #419685, was updated on 2001-04-27 19:12
You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=110894&aid=419685&group_id=10894

Category: Channel Types
Group: 8.3.3
Status: Open
Resolution: None
Priority: 5
Submitted By: Michael Kraus (mmg_kraus)
>Assigned to: Andreas Kupries (andreas_kupries)
>Summary: Problem with [file channels] if std channels not available

Initial Comment:
This occurs whenever Tcl could not initialize the 
standard channels (e.g. when it's running as a Windows 
NT service). Without any other open channels, [file 
channels] returns an empty list, which is correct. As 
soon as the first channel (e.g. a socket) is opened, 
it is registered as stdin, the next one as stdout, the 
third one as stderr. [file channels] returns {stdin 
stdout stderr}. Any additional open channel is 
returned with its Tcl name, e.g. sock123.

The problem is that I don't know how to prevent the 
first three sockets to be registered as the standard 
channels, and that [file channels sock*] does not 
return the list of all open sockets. (As a workaround, 
I create three dummy channels that do nothing.)

The man page for TclGetStdChannel sort of talks about 
that behavior, but only if "one of the standard 
channels is set to NULL, either by calling 
Tcl_SetStdChannel with a null channel argument, or by 
calling Tcl_Close on the channel". Since I'm doing 
pure Tcl here, it's hard to figure out what happens 
internally. Is this really the desired behavior of Tcl?

Looking at tclIO.c, I find that in Tcl_GetStdChannel() 
the statement "tsdPtr->stdinInitialized = 1" is done 
unconditionally, even when the preceeding "tsdPtr-
>stdinChannel = TclpGetDefaultStdChannel(TCL_STDIN)" 
returns NULL. This is the reason why, at the end of 
Tcl_CreateChannel(), the first programatically created 
channel is automatically registered as stdin, the next 
as stdout etc., even though these standard channels 
weren't really initialized (because they couldn't be 
obtained).

This conflicts with the documentation, since neither 
Tcl_SetStdChannel() was called with NULL, nor was 
Tcl_Close() called.

Proposed fix: In TclGetStdChannel(), do the "tsdPtr-
>stdinInitialized = 1" only when 
TclpGetDefaultStdChannel(TCL_STDIN) returned != NULL 
(and similar for stdout and stderr). That is, move 
those lines down a bit into the already existing if() 
statements. Is this the right solution (or is there 
not even a problem ;-)?

Diff for tclIO.c:

332d331
< 		tsdPtr->stdinInitialized = 1;
343a343
>             		tsdPtr->stdinInitialized = 1;
353d352
< 		tsdPtr->stdoutInitialized = 1;
354a354
>             		tsdPtr->stdoutInitialized = 1;
364d363
< 		tsdPtr->stderrInitialized = 1;
365a365
>             		tsdPtr->stderrInitialized = 1;


----------------------------------------------------------------------

You can respond by visiting: 
http://sourceforge.net/tracker/?func=detail&atid=110894&aid=419685&group_id=10894