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}(&stack_t(a)? >> _) : void =
"ext#new_ats"
extern
fun push {a:type}(&stack_t(a) >> _, a) : void =
"ext#push_ats"
extern
fun pop {a:type}(&stack_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+}(&stack_t(a) >> _) : Option(a) =
> "ext#pop_ats"
>
> should be changed to
>
> extern
> fun pop {a:type}(&stack_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 <stdatomic.h>
>> #include <stdlib.h>
>>
>> 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, &old_st};
>> if (atomic_compare_exchange_strong(st, &old_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+}(&stack_t(a)? >> _) : void =
>> "ext#new_ats"
>>
>> extern
>> fun push {a:t@ype+}(&stack_t(a) >> _, a) : void =
>> "ext#push_ats"
>>
>> extern
>> fun pop {a:t@ype+}(&stack_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 <stdio.h>
>>
>> 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
>>
>>
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