Tcl Source Code: View Ticket

Ticket UUID:	3592747
Title:	(tailcall\|yieldto) failed to find the proper namespace Abort
Type:	Bug	Created on:	2012-12-05 08:40:10
Submitter:	coldstore	Assigned to:	pooryorick
Subsystem:	60. NRE and coroutines	Severity:	Minor
Priority:	8	Last modified:	2018-06-28 18:48:32
Status:	Closed	Closed by:	dgp
Resolution:	Fixed	Closed on:	2018-06-28 18:48:32
Version:	None

Description:
Under some circumstances a coroutine can be invoked via ::yieldto while the namespace in which it resides is dying (nsPtr->flags&NS_DYING) This may occur, and is occuring, for example, when a TclOO object is being destroyed, and a coroutine within it is invoked by an event. The call to TclGetNamespaceFromObj() at tclBasic.c:8532 will indicate an error, because the current frame's namespace is not considered to match itself in the case that it is dying. I am unsure what the purpose of the test is, or under what circumstances the two namespaces might differ, but this abort occurs as a result of script evaluation, and hence should be considered a bug.
User Comments:
msofer added on 2012-12-05 17:36:45: 1. no script to repro? 2. any suggestion as to what should happen in that case? Would an error be in order? msofer added on 2012-12-05 17:45:00: Note: the problem is likely to appear also with [tailcall]. msofer added on 2012-12-06 09:39:05: The problem is indeed with [tailcall] whose guts are reused by [yieldto]. The current namespace was being cached in an nsNameType Tcl_Obj in order to insure its survival, and as a failure to resolve "could not happen" it was signaled by a panic. As colin is wont to do, he triggered the impossible! Fixed by using a better lifetime management of the namespace. msofer added on 2013-03-19 21:02:55: Is this bug still present? dkf added on 2013-03-20 16:27:56: This is why it's great to have a test, so we can confirm when the bug is dead… pooryorick added on 2018-06-23 17:00:22: The following script reproduces the issue: `namespace eval ns { proc p args { ::tailcall [namespace current] {}$args } namespace eval [namespace current] { namespace delete [namespace current] p } }` TIP 498 is one solution to this issue. pooryorick added on 2018-06-23 17:12:25: A slightly smaller example: `namespace eval ns { proc p args { ::tailcall [namespace current] {}$args } namespace delete [namespace current] p }` pooryorick added on 2018-06-23 21:28:39: If `{*}` from the example the compiled path for `tailcall` is taken, and in the compiled variant an error is raised: `namespace "::ns" not found` pooryorick added on 2018-06-24 07:24:20: In [9198c16407f3] namespace handling is removed from `TclNRTailcallObjCmd`, allowing `TclNRTailcallObjCmd` to handle namespace issues later. This aligns the behaviour of the non-compiled variant with the compiled one: An error is produced if the namespace is not found. dgp added on 2018-06-27 15:48:31: This is now fixed and the ticket can be closed?