How to allocate/free memory under @nogc

[Paul Backus]

On Thursday, 21 May 2020 at 02:50:22 UTC, data pulverizer wrote:
> I'm a bit puzzled about the whole `@nogc` thing. At first I 
> thought it just switched off the garbage collector and that you 
> had to allocate and free memory manually using `import 
> core.memory: GC;` I tried this and it failed because @nogc 
> means that the function can not allocate/free memory 
> (https://dlang.org/spec/function.html#nogc-functions). If this 
> is the case, how do you allocate/free memory without using the 
> garbage collector? Does allocating and freeing memory using 
> `GC.malloc` and `GC.free` avoid D's garbage collector? Also 
> what is the syntax for removing dangling pointers?

Marking a function @nogc means you can't use the garbage 
collector in that function, or call other functions that use it. 
It's still there, and functions that are not marked @nogc can 
still use it.

To allocate memory without the GC, you have a couple of options. 
The simplest is to use C's malloc function, which can be found in 
the core.stdc.stdlib module. A more complicated but more powerful 
option is to use a non-GC-based memory allocator from the 
std.experimental.allocator package. Either way, you will have to 
take care of freeing the memory yourself, either manually or 
using a technique like RAII.