Took a closer look.
'atstype_var' should be changed to 'atstype_boxed'.
The real problem is due to 'pop' being given an incorrect type.
I tried the following type to make the code work:
extern
fun pop {a:type}(_t(a) >> _) : (a) = "ext#pop_ats"
To mix C with ATS can be difficult. In particular, there is not much
documentation to help.
If you want Option(a) as the return type of 'pop', 'return x' in __cats_pop
needs to be changed to 'return __cats_some(x)' where '__cats_some' can
be implemented as follows:
extern
fun
none{a:type}(): Option(a) = "__cats_none"
extern
fun
some{a:type}(x:a): Option(a) = "__cats_some"
implement none() = None()
implement some(x) = Some(x)
Frankly speaking, without documentation, I don't feel that ATS2 is ready
for you to do what you wanted here.
On Mon, Nov 18, 2019 at 10:44 PM Vanessa McHale wrote:
> Thanks for the response!
>
> Unfortunately I still get trouble, viz.
>
> ...
>
> atstype_boxed pop_ats(atstype_ref st) { return __cats_pop(st); }
>
> atsvoid_t0ype new_ats(atstype_ref st) { __cats_new(st); }
>
> atsvoid_t0ype push_ats(atstype_ref st, atstype_boxed val) {
> __cats_push(st, val);
> }
> %}
>
> typedef stack_t(a: type) = $extype "struct stack_t"
>
> extern
> fun new {a:type}(_t(a)? >> _) : void =
> "ext#new_ats"
>
> extern
> fun push {a:type}(_t(a) >> _, a) : void =
> "ext#push_ats"
>
> extern
> fun pop {a:type}(_t(a) >> _) : Option(a) =
> "ext#pop_ats"
>
> fn print_str(x : string) : void =
> println!(x)
>
> ...
>
> leads to a segfault as before.
>
> Cheers,
> Vanessa
>
> On Sunday, November 17, 2019 at 10:18:54 PM UTC-6, gmhwxi wrote:
>>
>>
>> Each occurrence of {a:t@ype+} should be changed to {a:type}. E.g.,
>>
>> extern
>> fun pop {a:t@ype+}(_t(a) >> _) : Option(a) =
>> "ext#pop_ats"
>>
>> should be changed to
>>
>> extern
>> fun pop {a:type}(_t(a) >> _) : Option(a) = "ext#pop_ats"
>>
>> On Sunday, November 17, 2019 at 10:16:11 PM UTC-5, Vanessa McHale wrote:
>>>
>>> Hi all,
>>>
>>> I am trying to write a concurrent stack. Code is below:
>>>
>>> %{
>>> #include
>>> #include
>>>
>>> struct stack_t {
>>> void *value;
>>> struct stack_t *next;
>>> };
>>>
>>> void __cats_new(struct stack_t *st) {
>>> st->value = NULL;
>>> st->next = NULL;
>>> }
>>>
>>> void __cats_push(struct stack_t *st, void *val) {
>>> for (;;) {
>>> struct stack_t old_st = *st;
>>> struct stack_t new_st = {val, _st};
>>> if (atomic_compare_exchange_strong(st, _st, new_st))
>>> return;
>>> }
>>> }
>>>
>>> // ignore ABA problem
>>> void *__cats_pop(struct stack_t *st) {
>>> for (;;) {
>>> if (st->next == NULL)
>>> return NULL;
>>> struct stack_t *old_st = st;
>>> struct stack_t xs1 = *(st->next);
>>> void *x = st->value;
>>> if (atomic_compare_exchange_strong(st, old_st, xs1))
>>> return x;
>>> }
>>> }
>>>
>>> atstype_boxed pop_ats(atstype_ref st) { return __cats_pop(st); }
>>>
>>> atsvoid_t0ype new_ats(atstype_ref st) { __cats_new(st); }
>>>
>>> atsvoid_t0ype push_ats(atstype_ref st, atstype_var val) {
>>> __cats_push(st, val);
>>> }
>>> %}
>>>
>>> typedef stack_t(a: t@ype+) = $extype "struct stack_t"
>>>
>>> extern
>>> fun new {a:t@ype+}(_t(a)? >> _) : void =
>>> "ext#new_ats"
>>>
>>> extern
>>> fun push {a:t@ype+}(_t(a) >> _, a) : void =
>>> "ext#push_ats"
>>>
>>> extern
>>> fun pop {a:t@ype+}(_t(a) >> _) : Option(a) =
>>> "ext#pop_ats"
>>>
>>> fn print_str(x : string) : void =
>>> println!(x)
>>>
>>> implement main0 (argc, argv) =
>>> let
>>> var st: stack_t(string)
>>> val () = new(st)
>>> val () = push(st, "res")
>>> val () = push(st, "res2")
>>> val- Some (x) = pop(st)
>>> val () = print_str(x)
>>> in end
>>>
>>> (This compiles with gcc; I can run it with patscc simple.dats -latomic ;
>>> ./a.out)
>>>
>>> Unfortunately, it immediately segfaults. I know that the offending line
>>> is the
>>>
>>> val () = print_str(x)
>>>
>>> because removing it makes the program run fine.
>>>
>>> I tried writing an equivalent program in C, viz.
>>>
>>> #include
>>>
>>> int main(int argc, char *argv[]) {
>>>
>>> struct stack_t *st;
>>>
>>> __cats_push(st, "res");
>>> __cats_push(st, "res2");
>>>
>>> char *res;
>>>
>>> res = __cats_pop(st);
>>> printf("%s\n", res);
>>>
>>> res = __cats_pop(st);
>>> printf("%s\n", res);
>>> }
>>>
>>> ...which works as expected. So I believe I am misunderstanding how ATS
>>> handles FFI and how structures exist in memory.
>>>
>>> Any insight is appreciated!
>>>
>>> Thanks,
>>> Vanessa
>>>
>>> --
> You received this message because you are subscribed to the Google Groups
> "ats-lang-users" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to ats-lang-users+unsubscr...@googlegroups.com.
> To view this discussion on the web visit
>
