Tcl Source Code: View Ticket

Ticket UUID:	ac601b59bab79fbe0559f19f65620c28a3287517
Title:	using the Thread package in a debugging build of Tcl results in a segmentation fault at exit
Type:	Bug	Version:	8.7
Submitter:	pooryorick	Created on:	2022-03-21 21:50:50
Subsystem:	- New Builtin Commands	Assigned To:	pooryorick
Priority:	5 Medium	Severity:	Important
Status:	Closed	Last Modified:	2022-04-14 10:33:21
Resolution:	Fixed	Closed By:	jan.nijtmans
		Closed on:	2022-04-14 10:33:21
Description:	(text/x-fossil-wiki) In a debugging build of core_8_branch, a script that does nothing more than require the Thread package results in a segmentation fault when the process exits. This is due to the fact that since commit [3b0e92b198], <code>LoadCleanupProc()</code> unloads every loaded library when an interp is deleted. Later, <code>FinalizeThread()</code> calls exit handlers set up by the Thread library, but those handlers have been unloaded, causing a segmentation fault.
User Comments:	jan.nijtmans added on 2022-04-14 10:33:21: (text/x-fossil-wiki) Since the fix is in core-8-branch now, this ticket can be closed. Thanks, pooryorick, for the fix! pooryorick added on 2022-03-22 00:52:43: (text/x-fossil-wiki) Fixed in [f0a6d62a1ade872d]. With this fix, a library is only unloaded from the process if it provides a "Unload" function. Since it requires some care to produce a library fit for dynamic unloading, it makes sense to limit unload functionality only to those libraries specifically designed to support it. Checking for the existence of an "Unload" function is a good way to differentiate between modules that can be unloaded, and modules that cannot.