On Wed 01 Mar 2017 16:11, Josep Portella Florit <j...@primfilat.com> writes:
> Hi Andy, > > On 02/28/2017 03:17 PM, Andy Wingo wrote: >> On Tue 30 Jun 2015 15:50, Josep Portella Florit <j...@primfilat.com> writes: >> >>> This code crashes Guile 2.0.11: >>> >>> (define x (make-dynamic-state)) >>> (with-dynamic-state x (lambda () (/ 1 0))) >> >> Sad :/ Fixed in 2.2 though, finally. I don't really know how to fix it >> in 2.0 though. Marking as closed given that we will have a shiny new >> 2.2.0 soon. > > Good work! Do I have to wait until you release 2.2.0 to test it? > (Today I've tested it with 2.1.7.22-fcebf and it still crashed.) Ack, I didn't actually test it! I thought a related fix in 2.1.7 would have caught it. I will have a look. > BTW, did you change your mind on deprecating dynamic states? > <http://lists.gnu.org/archive/html/guile-devel/2016-06/msg00104.html> Yes, with a caveat. Having captured dynamic states also be mutable places was untenable, as you could have multiple threads mutating the same place at one time. However dynamic states work well as a way to transport a parameterization from one part of the code to another. I rely on them in Fibers for this purpose. What do you think? :) See NEWS: ** Fix too-broad capture of dynamic stack by delimited continuations Guile was using explicit stacks to represent, for example, the chain of current exception handlers. This means that a delimited continuation that captured a "catch" expression would capture the whole stack of exception handlers, not just the exception handler added by the "catch". This led to strangeness when resuming the continuation in some other context like other threads; "throw" could see an invalid stack of exception handlers. This has been fixed by the addition of the new "fluid-ref*" procedure that can access older values of fluids; in this way the exception handler stack is now implicit. See "Fluids and Dynamic States" in the manual, for more on fluid-ref*. And: ** Dynamic states capture values, not locations Dynamic states used to capture the locations of fluid-value associations. Capturing the current dynamic state then setting a fluid would result in a mutation of that captured state. Now capturing a dynamic state simply captures the current values, and calling `with-dynamic-state' copies those values into the Guile virtual machine instead of aliasing them in a way that could allow them to be mutated in place. This change allows Guile's fluid variables to be thread-safe. To capture the locations of a dynamic state, capture a `with-dynamic-state' invocation using partial continuations instead. Andy
