On Thursday, 28 February 2019 at 03:33:25 UTC, Sam Johnson wrote:
```
string snappyCompress(const string plaintext) {
import deimos.snappy.snappy : snappy_compress,
snappy_max_compressed_length, SNAPPY_OK;
import core.stdc.stdlib : malloc, free;
import std.string : fromStringz, toStringz;
char *input = cast(char *) toStringz(plaintext);
size_t output_length =
snappy_max_compressed_length(plaintext.length);
char *output = cast(char *) malloc(output_length);
if(snappy_compress(input, plaintext.length, output,
&output_length) == SNAPPY_OK) {
string ret = (cast(string) fromStringz(output)).clone();
// <---- do something magical here
return ret;
}
assert(0);
}
```
How can I get the GC to automatically garbage collect the
`output` malloc call by tracking the returned `ret` reference?
I'm surprised that GC.addRoot(output) actually helped you here,
GC.addRoot is for when the thing you are adding may hold pointers
to GC allocated stuff and you don't want non-GC allocated
references to dangle when the GC does a collection pass.
If you want the GC to handle it just use new:
char[] output = new char[output_length];
...
return assumeUnique(output);
Or is this already managed by the gc because I cast to a
`string`?
No, string is just an alias for immutable(char)[], which is just
struct
{
size_t length;
immutable(char)* ptr;
}
it can refer to any span of memory, it has no concept of
ownership.
