Indefinite Array in Struct Fails on Access

[cod3monk]

When compiling the following code with impala (2ab3ab4)

struct CS {
    sizes : [i32],
    count : i32,
}

fn main() -> i32 {
 let cache_sizes = CS {sizes: [32*1024, 256*1024, 20*1024*1024], count: 3}; // in bytes
 
 for i in range(0, cache_sizes.count) {
     print_int(cache_sizes.sizes(i));
 }
 
 0
}

Impala fails with the following message:

Assertion failed: ((!r || dynamic_cast<L*>(r)) && "cast not possible"), function scast, file dev/anydsl/thorin/src/thorin/util/cast.h, line 26.
Abort trap: 6

I don't see the cast here and the same code works if sizes and count are not in a struct but two local variables.

[FanyuYe]

Hi. For declaring a variable with an array type I used "&[i32]" rather than "[i32]". Hope this helps.

[cod3monk]

@FanyuYe Where? In the struct definition? That leads to lvalue required for unary '&' operand

[FanyuYe]

This is because you try to assign value to it. So you have to declare it use 'mut' key word.
E.g.
let mut cache_sizes = ...;

[richardmembarth]

• You can either use an definite array (of size 3):

struct CS {
    sizes : [i32 * 3],
    count : i32,
}

let cache_sizes = CS {sizes: [32*1024, 256*1024, 20*1024*1024], count: 3}; // in bytes

for i in range(0, cache_sizes.count) {
    print_int(cache_sizes.sizes(i));
} 

Writing to cache_sizes.sizes requires cache_sizes to be mutable: let mut cache_sizes.

• You can use a reference to an indefinite array:

struct CS {
    sizes : &[i32],
    count : i32,
}   

let cache_sizes = CS {sizes: [32*1024, 256*1024, 20*1024*1024], count: 3}; // in bytes

for i in range(0, cache_sizes.count) {
    print_int(cache_sizes.sizes(i));
}

Writing to cache_sizes.sizes requires then sizes of the CS struct to be mutable: sizes: &mut[i32].

[cod3monk]

The latter does not work here (also not with making cache_size mutable), the first I already had as a work-around.

[cod3monk]

It is not a big issue, just an annoyance.

[leissa]

Originally, the idea was to support variable length arrays and flexible array members as in C99. But this has never been thoroughly implemented. Also, we'd like to change a couple of things how anydsl handles arrays in future versions anyway.
However, in the meantime I can add a check in the semantic analysis which rejects such usage of indefinite arrays.

[cod3monk]

Sounds good, would have saved me some time ;)

[leissa]

Can I close this bug with the last commit?

[cod3monk]

Works for me. Thanks