digitalmars.D.learn - does the shared keyword work with mutable structs?
- WhatMeWorry (43/43) Mar 08 2018 I read where shared classes have not been implemented yet. So I'm
- Kagamin (2/2) Mar 09 2018 spawn doesn't infer `ref` storage class and copies eventBuffer by
- Kagamin (2/2) Mar 09 2018 To make a struct noncopyable, add @disable this(this); to it,
- WhatMeWorry (13/15) Mar 09 2018 I tried the @disable this(this); but now it doesn't even compile?
- Jonathan M Davis (11/26) Mar 09 2018 Well, as Kagamin said, the compiler gives you an error if you
- Steven Schveighoffer (14/23) Mar 13 2018 Use pointers for passing:
I read where shared classes have not been implemented yet. So I'm using just a struct e below: But the output below is showing that sharing is not happening between Struct in main() and the various spawned threads. I'm I doing something wrong? creating queue in EventBuffer constructor eventBuffer.enter = 1 eventBuffer.leave = 0 eB.enter = 0 eB.enter = 0 eB.leave = 0 eB.leave = 0 eB.enter = 0 eB.leave = 0 void producer(in ref shared(EventBuffer) eB, shared(Lock) lock) { writeln("eB.enter = ", eB.enter); writeln("eB.leave = ", eB.leave); Event event; foreach(i; 0..7) { synchronized(lock) { event.keyPressed = i; eB.enterOrLeaveQueue(Direction.Entering, event); } } } void main() { shared(Lock) lock = new shared(Lock)(); shared(EventBuffer) eventBuffer = EventBuffer(50); writeln("eventBuffer.enter = ", eventBuffer.enter); writeln("eventBuffer.leave = ", eventBuffer.leave); foreach(i; 0..3) { spawn(&producer, eventBuffer, lock); } }
Mar 08 2018
spawn doesn't infer `ref` storage class and copies eventBuffer by value.
Mar 09 2018
To make a struct noncopyable, add disable this(this); to it, then compiler will give an error on an attempt to copy it.
Mar 09 2018
On Friday, 9 March 2018 at 10:42:47 UTC, Kagamin wrote:To make a struct noncopyable, add disable this(this); to it, then compiler will give an error on an attempt to copy it.I tried the disable this(this); but now it doesn't even compile? Error: template std.concurrency.spawn cannot deduce function from argument types !()(void function(shared(EventBuffer) eB, shared(Lock) lock), shared(EventBuffer), shared(Lock)), candidates are: C:\ldc2\bin\..\import\std\concurrency.d(464): std.concurrency.spawn(F, T...)(F fn, T args) if (isSpawnable!(F, T)) Is std.concurrency a work in progress or I'm I just obtuse here? I've been reading Ali's book on the concurrency chapters as inspiration, but the examples there use simple data types like ints or bools.
Mar 09 2018
On Friday, March 09, 2018 19:33:26 WhatMeWorry via Digitalmars-d-learn wrote:On Friday, 9 March 2018 at 10:42:47 UTC, Kagamin wrote:Well, as Kagamin said, the compiler gives you an error if you disable this(this); and then the code attempts to copy the type. The point was to catch when the type was copied, not make spawn work with your type. spawn requires that the types that its given be copyable. Either your type needs to be able to work if it's copied, or it needs to be a reference type (either by using a class, a pointer to a struct, or by making the struct's guts live on the heap with a member variable that's a pointer pointing to them). - Jonathan M DavisTo make a struct noncopyable, add disable this(this); to it, then compiler will give an error on an attempt to copy it.I tried the disable this(this); but now it doesn't even compile? Error: template std.concurrency.spawn cannot deduce function from argument types !()(void function(shared(EventBuffer) eB, shared(Lock) lock), shared(EventBuffer), shared(Lock)), candidates are: C:\ldc2\bin\..\import\std\concurrency.d(464): std.concurrency.spawn(F, T...)(F fn, T args) if (isSpawnable!(F, T)) Is std.concurrency a work in progress or I'm I just obtuse here? I've been reading Ali's book on the concurrency chapters as inspiration, but the examples there use simple data types like ints or bools.
Mar 09 2018
On 3/9/18 2:33 PM, WhatMeWorry wrote:On Friday, 9 March 2018 at 10:42:47 UTC, Kagamin wrote:Use pointers for passing: void producer(in shared(EventBuffer) *eB, shared(Lock) lock) ... spawn(&producer, &eventBuffer, lock); The disable postblit is to prevent you from doing what you did -- passing a value type expecting it gets passed by reference. In order to avoid the error you must use a reference.To make a struct noncopyable, add disable this(this); to it, then compiler will give an error on an attempt to copy it.I tried the disable this(this); but now it doesn't even compile?Is std.concurrency a work in progress or I'm I just obtuse here?It's not a work in progress, though there are always chances there are bugs there. We fixed one not too long ago in which it didn't work with certain types.I've been reading Ali's book on the concurrency chapters as inspiration, but the examples there use simple data types like ints or bools.TBH, the best things to pass as messages are value types or immutables. But obviously, if you need to share something, you need to use shared. -Steve
Mar 13 2018