Make synchronized statement `nothrow`

[dlangBugzillaToGithub]

Denis Shelomovskii reported this on 2013-10-10T06:09:20Z

Transferred from https://issues.dlang.org/show_bug.cgi?id=11216

CC List

• Walter Bright
• Martin Nowak
• FeepingCreature
• Vladimir Panteleev
• Mathias LANG

Description

Currently this code fails to compile because `_d_criticalenter` and `_d_criticalexit` are not `nothrow`:
---
void f() nothrow
{ synchronized { } }
---

This is because user supplied monitor can throw as `lock`/`unlock` methods of `Object.Monitor` are not `nothrow`.

Dependent druntime functions like `rt_attachDisposeEvent` and `rt_detachDisposeEvent` are thus not `nothrow` too.


The proposal is to mark user supplied monitor `lock`/`unlock` methods also `nothrow`. In the case it will be rejected documentation note about the fact synchronized statement is not `nothrow` should be added.

[dlangBugzillaToGithub]

verylonglogin.reg commented on 2013-10-10T06:14:31Z

Also in the case in the description are there any possibilities to supply a user monitor? If not, this subcase is clearly a "rejects-valid" bug.

[dlangBugzillaToGithub]

code commented on 2014-10-01T08:18:28Z

I'm in favor of doing this. Is there a migration path for requiring nothrow on the Monitor Interface without breaking code?

[dlangBugzillaToGithub]

bugzilla commented on 2014-11-08T04:40:20Z

https://github.com/D-Programming-Language/dmd/pull/4115

[dlangBugzillaToGithub]

github-bugzilla commented on 2014-11-08T22:40:17Z

Commits pushed to master at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/47c679964003ca75290e3174df85b0641eb5d282
fix Issue 11216 - Make synchronized statement `nothrow`

- mark _d_monitorenter/exit as nothrow

https://github.com/D-Programming-Language/dmd/commit/dc118391e51ddb69093780c157b1ca41e26add90
Merge pull request #4115 from MartinNowak/fix11216

fix Issue 11216 - Make synchronized statement `nothrow`

[dlangBugzillaToGithub]

github-bugzilla commented on 2014-12-12T15:42:04Z

Commits pushed to master at https://github.com/D-Programming-Language/druntime

https://github.com/D-Programming-Language/druntime/commit/05b15ab05279a70b30f4a580c705526e70e09155
fix Issue 11216 - Make synchronized statement `nothrow`

- require Object.Monitor lock and unlock functions to be nothrow

- change methods of all core.sync classes to nothrow

https://github.com/D-Programming-Language/druntime/commit/46061e646ae547d297aeae448eb246e251118344
Merge pull request #1013 from MartinNowak/fix11216

fix Issue 11216 - Make synchronized statement `nothrow`

[dlangBugzillaToGithub]

github-bugzilla commented on 2015-02-18T03:38:26Z

Commits pushed to 2.067 at https://github.com/D-Programming-Language/druntime

https://github.com/D-Programming-Language/druntime/commit/05b15ab05279a70b30f4a580c705526e70e09155
fix Issue 11216 - Make synchronized statement `nothrow`

https://github.com/D-Programming-Language/druntime/commit/46061e646ae547d297aeae448eb246e251118344
Merge pull request #1013 from MartinNowak/fix11216

[dlangBugzillaToGithub]

github-bugzilla commented on 2015-02-18T03:39:19Z

Commits pushed to 2.067 at https://github.com/D-Programming-Language/dmd

https://github.com/D-Programming-Language/dmd/commit/47c679964003ca75290e3174df85b0641eb5d282
fix Issue 11216 - Make synchronized statement `nothrow`

https://github.com/D-Programming-Language/dmd/commit/dc118391e51ddb69093780c157b1ca41e26add90
Merge pull request #4115 from MartinNowak/fix11216

[dlangBugzillaToGithub]

pro.mathias.lang commented on 2015-10-18T09:28:15Z

Well, since it was reverted, it should have been reopened.

Revert in DMD: https://github.com/D-Programming-Language/dmd/pull/4459
Revert in Druntime: https://github.com/D-Programming-Language/druntime/pull/1188

[dlangBugzillaToGithub]

mathias.lang commented on 2016-05-10T17:27:26Z

*** Issue 16009 has been marked as a duplicate of this issue. ***

[dlangBugzillaToGithub]

default_357-line commented on 2018-02-23T16:14:19Z

Still an issue in 2018.

[dlangBugzillaToGithub]

default_357-line commented on 2018-02-23T16:19:53Z

Istm a possible approach would be:

 * Define SimpleMonitor : Monitor with nothrow

 * change DMD to use nothrow when locking SimpleMonitors

 * subclass druntime's Mutex with SimpleMutex : Mutex, SimpleMonitor

 * use SimpleMutex as the mutex implementation for class monitors

Then synchronized(this) should be nothrow without breaking existing code that depends on Mutex/Monitor. It would only break if you were assigning to _monitor, and that's easily fixed by using a separate member.

I don't know how to implement this on the DMD side though.