I came came across an unexpected problem with spawn recently and thought I
would mention it here in the hope that someone can clarify the situation.
The program below behaves erratically when compiled with --threads:on --gc:arc.
Sometimes it runs ok, sometimes it reports 'SIGSEGV: Illegal storag
Hi Araq
The dev version of nim-1.9.3
(2023-05-08-devel-71f2e1a502ad231e3356217398e2d7fcd6137967) does not seem to
offer me the option of --mm:atomicArc (I am using linux_x64) but with --mm:arc
it runs the example code without any errors.
I guess nim-1.6.12 that gives the problem has some subtl
FWIW this code crashes about 50% of the time with nim v1.6 + arc
std/threadpool
type
Ans = ref object
x: float
Tmp = ref object
a,b,c,d,e,f,g,h,i,j,k : seq[float]
proc calc( x:Tmp ): Ans =
result = new(Ans)
let n = 4
Th documentation says that procedures marked with 'lent' return a hidden
pointer. But the code below prints two different values which shows that a copy
of the data is being returned instead of a pointer (Nim version 2.0.0 used) . I
assume that I am misunderstanding how 'lent' works, can anyone
Very many thanks for the explanation, now I see what is happening.
I was developing some code using Malebolgia and found an unexpected problem.
This example code crashes crashes about 80% of the time when I run it:
type Svec* = ref array[19,float]
proc subfn( svec:Svec ) = discard 0
proc fn( svec:ptr Svec ) =
let svec = svec[
Many thanks for explanation, and using atomicArc solves the problem. Somehow I
never quite realised that Nim reference counting was playing a role here and
would be affected by data races.
Thank you for the useful suggestion. The cursor pragma is turning out to be
very useful in my code - maybe it could be upgraded into some kind of keyword
in a future Nim version.
The malebolgia documentation says that if a spawned task raises an exception
then it will be rethrown after awaitAll. But the example code given below does
not seem to do this: it prints 'other error' and only when I i remove 'm.spawn'
does it print 'my error'.
Very likely I am misunderstanding
Many thanks for the prompt reply and the info. But why is malebolgia doing this
(it seems a strange thing to do), and how can I get malebolgia to return the
desired error type?
(The ValueError that malebolgia returns in this example does contain "MyError"
in its message string so if all else fa
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