Memory management by interfacing C/C++

[9il]

On Saturday, 27 April 2019 at 22:25:58 UTC, Ferhat Kurtulmuş 
wrote:
> Hi,
>
> I am wrapping some C++ code for my personal project (opencvd), 
> and I am creating so many array pointers at cpp side and 
> containing them in structs. I want to learn if I am leaking 
> memory like crazy, although I am not facing crashes so far. Is 
> GC of D handling things for me? Here is an example:
>
> ```
> //declaration in d
> struct IntVector {
>     int* val;
>     int length;
> }
>
> // in cpp
> typedef struct IntVector {
>     int* val;
>     int length;
> } IntVector;
>
> // cpp function returning a struct containing an array pointer 
> allocated with "new" op.
> IntVector Subdiv2D_GetLeadingEdgeList(Subdiv2D sd){
>     std::vector<int> iv;
>     sd->getLeadingEdgeList(iv);
>
>     int *cintv = new int[iv.size()]; // I don't call delete 
> anywhere?
>
>     for(size_t i=0; i < iv.size(); i++){
>         cintv[i] = iv[i];
>     }
>     IntVector ret = {cintv, (int)iv.size()};
>     return ret;
> };
>
> // call extern c function in d:
> extern (C) IntVector Subdiv2D_GetLeadingEdgeList(Subdiv2d sd);
>
> int[] getLeadingEdgeList(){
>     IntVector intv = Subdiv2D_GetLeadingEdgeList(this);
>     int[] ret = intv.val[0..intv.length]; // just D magic. 
> Still no delete anywhere!
>     return ret;
> }
> ```
>
> The question is now: what will happen to "int *cintv" which is 
> allocated with new operator in cpp code? I have many code 
> similar in the project, but I have not encounter any problem so 
> far even in looped video processings. Is GC of D doing 
> deallocation automagically?
> https://github.com/aferust/opencvd

Hello Ferhat,

You can use RCArray!T or Slice!(RCI!T) [1, 2] as common thread 
safe @nogc types for D and C++ code.
See also integration C++ example [3] and C++ headers [4].


RCArray (fixed length)
[1] http://mir-algorithm.libmir.org/mir_rc_array.html
RCSlice (allows to get subslices)
[2] 
http://mir-algorithm.libmir.org/mir_ndslice_allocation.html#rcslice
C++ integration example
[3] 
https://github.com/libmir/mir-algorithm/tree/master/cpp_example
C++ headers
[4] 
https://github.com/libmir/mir-algorithm/tree/master/include/mir