Can't I allocate at descontructor?

[tsbockman]

On Friday, 5 March 2021 at 21:02:08 UTC, H. S. Teoh wrote:
> If you know when you can deallocate something, that means you 
> don't need the GC to collect it, so you could just allocate it 
> on the malloc heap instead, and call destroy/free once you're 
> done.  You could use the C version of malloc/free.  You can 
> also optionally use GC.malloc/GC.free.
>
> E.g.:
>
> 	class C {...}
>
> 	import core.memory : GC;
> 	C c = cast(C) GC.malloc(C.sizeof);
> 	... // use c
>
> 	// We're done with c, destroy it
> 	destroy(c);	// this will call the dtor
> 	GC.free(cast(void*) c);
> 	c = null; // optional, just to ensure we don't accidentally 
> use it again

Unless the function is nothrow, that should really be:

     import core.memory : GC;
     C c = cast(C) GC.malloc(C.sizeof);
     scope(exit) {
         // We're done with c, destroy it
         destroy(c);	// this will call the dtor
         GC.free(cast(void*) c);
         c = null; // optional, just to ensure we don't 
accidentally use it again
     }
     ... // use c

Or,

     import core.memory : GC;
     C c = cast(C) GC.malloc(C.sizeof);
     try {
         ... // use c
     } finally {
         // We're done with c, destroy it
         destroy(c);	// this will call the dtor
         GC.free(cast(void*) c);
         c = null; // optional, just to ensure we don't 
accidentally use it again
     }