Allow a fiber in HOLD state to be reset bypassing scope(exit) etc.

[Dzugaru]

Discussion: http://forum.dlang.org/thread/bltdzwskligncpgwdmxc@forum.dlang.org

[MartinNowak]

That's actually much more confusing than before.

One should only reset a fiber in term state, because resetting it in hold state won't cleanup the stack, e.g. scope(exit) and struct destructors aren't called.

[MartinNowak]

Looking at the implementation again, there is indeed a bug.
The assert( m_ctxt.tstack == m_ctxt.bstack ); in reset will only work for terminated fibers not for hold ones. We'd need to explicitly set m_ctxt.tstack = m_ctxt.bstack for those.

[Dzugaru]

Now I get it, reset without parameters works for HOLD state iff the stack is clean. Reset with parameters (new function/delegate) works with any state cause there is no check there and leads to stack overflow.

We'd need to explicitly set m_ctxt.tstack = m_ctxt.bstack for those.

That would be awesome, one could cope with scope(exit) and struct destructors not executing but having a way to completely reset HOLD fiber is very nice.

[MartinNowak]

We'd need to explicitly set m_ctxt.tstack = m_ctxt.bstack for those.

Can you change the pull to just do that and add a test case.

unittest
{
    // test unsafe reset in hold state
    auto fib = new Fiber({ubyte[2048] buf = void; Fiber.yield();}, 4096);
    foreach (_; 0 .. 10)
    {
        fib.call();
        assert(fib.state == Fiber.State.HOLD);
        fib.reset();
    }
}

[Dzugaru]

Can you change the pull to just do that and add a test case.

Did that, rebuilt everything with Digger on win32 and that test case works.

[MartinNowak]

Auto-merge toggled on

[MartinNowak]

Thx