4 ms·

>if you have a heap allocated thing that is passed between Rust and C++, who frees it? Isn't this an issue regardless? Forget crossing the rust/c++ boundary, l

by xxpor 6y ago

>if you have a heap allocated thing that is passed between Rust and C++, who frees it? Isn't this an issue regardless? Forget crossing the rust/c++ boundary, lets say you pass something to another class in c++, you need to have a contract of who frees what when, right? Maybe I'm not understanding the issue.

webkike 6y ago
There are some things that make this better, such as returning pointer types and not returning raw pointers. Returning raw pointers usually means that another function will delete them. I very rarely see pointers handed back from functions being freed caller side
- Matthias247 6y ago
  Do you mean references instead of pointers? I'm not familiar of a difference between pointers and raw pointers in C or C++. C++ allows to be more clear: unique_ptrs allow to move ownership, references mean this is definitely not owned, and the remaining questions are around normal pointers. With pure C there is however zero distinction. A pointer can mean ownership is transferred, it is meant to be a reference, it could be a static reference to something in constant memory, etc.
  - webkike 6y ago
    I meant pointers versus types such unique_ptr and shared_ptr
    - Snelius 6y ago
      You will lost his (*_ptr) magic cuz types match is not compatible. Mem must be free on the allocation side, kind of law.
edflsafoiewq 6y ago
RAII usually handles all that.
Paul-ish 6y ago
Inside both Rust and C++ there are very well developed tools (eg smart pointers) for dealing with memory allocations. These tools were never written to be compatible with each other, so you lose them at the language boundary.
- xxpor 6y ago
  That makes sense. I do 99% C, so any time I even have to think about C++ it unfortunately turns into C with classes rather than C++, so I'm really not as familiar with the smart pointer options.

4 ms·

>if you have a heap allocated thing that is passed between Rust and C++, who frees it? Isn't this an issue regardless? Forget crossing the rust/c++ boundary, l

by xxpor 6y ago

webkike 6y ago
There are some things that make this better, such as returning pointer types and not returning raw pointers. Returning raw pointers usually means that another function will delete them. I very rarely see pointers handed back from functions being freed caller side
- Matthias247 6y ago
  Do you mean references instead of pointers? I'm not familiar of a difference between pointers and raw pointers in C or C++. C++ allows to be more clear: unique_ptrs allow to move ownership, references mean this is definitely not owned, and the remaining questions are around normal pointers. With pure C there is however zero distinction. A pointer can mean ownership is transferred, it is meant to be a reference, it could be a static reference to something in constant memory, etc.
  - webkike 6y ago
    I meant pointers versus types such unique_ptr and shared_ptr
    - Snelius 6y ago
      You will lost his (*_ptr) magic cuz types match is not compatible. Mem must be free on the allocation side, kind of law.
edflsafoiewq 6y ago
RAII usually handles all that.
Paul-ish 6y ago
Inside both Rust and C++ there are very well developed tools (eg smart pointers) for dealing with memory allocations. These tools were never written to be compatible with each other, so you lose them at the language boundary.
- xxpor 6y ago
  That makes sense. I do 99% C, so any time I even have to think about C++ it unfortunately turns into C with classes rather than C++, so I'm really not as familiar with the smart pointer options.