On Tuesday, 10 May 2016 at 17:46:17 UTC, Vladimir Panteleev wrote:
Here is the situation, AIUI:
1. We allow users to provide their own Monitors, which hook
into the synchronized(obj) statement.
2. These monitors' methods are unadorned (no nothrow/@nogc).
3. As a result, synchronized(obj) statements will not compile
in nothrow/@nogc code, because we can't know that the Monitor
implementation doesn't throw / use the GC.
4. As Matthias mentioned, fixing this was attempted before (by
making the Monitor methods `nothrow`). However, this broke code
(vibe.d specifically), as its implementation was actually not
`nothrow`: https://issues.dlang.org/show_bug.cgi?id=11216
This is a problem e.g. in Druntime code, because it currently
forces a lot of code that should be `nothrow` to not be
annotated as such, even when the synchronization objects used
use the standard D monitor implementation, which is actually
`nothrow`.
So I guess the way forward here for the Druntime code is to
abandon the synchronized() statement and use locks directly?
As far as I remember, the issue was not the design, but that it
required a design change on Vibe.d's side.
See
https://github.com/rejectedsoftware/vibe.d/pull/972#issuecomment-75714736 where Sonke mentions that "actually mutexes in vibe.d are never nothrow".
However, since some of the internals of Vibe.d are now supported
upstream, the problem might disappear in a foreseeable future.
