# Are \`jl\_value\_t\*\*\` compatible with \`jl\_array\_t\*\`? If not, how do I manage \`Any\[\]\` in C?
**URL:** https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390
**Category:** General Usage
**Tags:** question
**Created:** [October 16, 2018, 8:24am UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390 "2018-10-16T08:24:23Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@kim366](https://discourse.julialang.org/u/kim366)
#### Post date: [October 16, 2018, 8:24am UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/1 "2018-10-16T08:24:23Z")
The [Docs](https://docs.julialang.org/en/stable/manual/embedding/) show the following:
```julia
double *existingArray = (double*)malloc(sizeof(double)*10);
jl_array_t *x = jl_ptr_to_array_1d(array_type, existingArray, 10, 0);
```
I thought I could use `jl_value_t**` instead of `double*` in this case, but when giving this array to a julia function, I just get random values as the elements (probably because it is interpreting the type information).
But how then, would you manage an `Any[]` in Julia if there is no type information on each element? Do I need a different approach or is this something that is just not implemented?
Thanks for the help!
---
### Author:  [@kim366](https://discourse.julialang.org/u/kim366)
#### Post date: [October 16, 2018, 8:25am UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/2 "2018-10-16T08:25:47Z")
Huh, I think I know the issue: I still use float64 as the datatype… I’ll try changing that when I get home
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### Author:  [@kim366](https://discourse.julialang.org/u/kim366)
#### Post date: [October 17, 2018, 6:05am UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/3 "2018-10-17T06:05:02Z")
Ey, it does indeed work when using `jl_any_type`!
```nohighlight
jl_value_t* array_type{jl_apply_array_type(
reinterpret_cast(jl_any_type), dimensions)};
jl_value_t** _arr = new jl_value_t*[_size];
_metadata = jl_ptr_to_array_1d(array_type, _arr, _size, true);
```
---
### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [October 17, 2018, 3:14pm UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/4 "2018-10-17T15:14:03Z")
The way you allocate the `jl_value_t*` array is wrong. `jl_ptr_to_array_1d(..., true)` only accept `malloc` allocated pointers.
Also, even though your code doesn’t have any other issue yet, you must not mutate `arr` after you created `metadata` unless you also trigger the write barrier.
---
### Author:  [@kim366](https://discourse.julialang.org/u/kim366)
#### Post date: [October 25, 2018, 9:32pm UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/5 "2018-10-25T21:32:40Z")
Really? Are new and malloc different on the inside? I didn’t know. It currently works with new, but I’ll change it just to be safe
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### Author:  [@yuyichao](https://discourse.julialang.org/u/yuyichao)
#### Post date: [October 27, 2018, 1:06am UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/6 "2018-10-27T01:06:50Z")
> [@kim366](#):
>
> Really? Are new and malloc different on the inside?
Yes. They have to (in general). For POD, there can be some room to be flexible but that’s definitely undefined behavior.
---
### Author:  [@kim366](https://discourse.julialang.org/u/kim366)
#### Post date: [October 28, 2018, 2:39pm UTC](https://discourse.julialang.org/t/are-jl-value-t-compatible-with-jl-array-t-if-not-how-do-i-manage-any-in-c/16390/7 "2018-10-28T14:39:27Z")
Interesting. I will switch my code then