Antipattern in core.memory.GC.addRange?
safety0ff
safety0ff.dev at gmail.com
Sat Sep 23 05:30:08 UTC 2017
On Friday, 22 September 2017 at 21:29:10 UTC, Steven
Schveighoffer wrote:
> GC.addRange has this signature:
>
> static nothrow @nogc void addRange(in void* p, size_t sz, const
> TypeInfo ti = null);
>
> I see a large problem with this. Let's say you malloc an array
> of struct pointers:
>
> struct Foo { ... }
>
> import core.stdc.stdlib;
> auto ptrs = (cast(Foo *)malloc(Foo.sizeof * 10))[0 .. 10];
>
> Now, you want to store GC pointers in that block, you need to
> add the range to the GC:
>
> GC.addRange(ptrs.ptr, ptrs.length);
>
> See the problem?
Yes, you forgot to multiply by Foo.sizeof.
Using the pattern from the example in the documentation,
the code would be:
size_t bytes = Foo.sizeof * 10;
auto ptrs = (cast(Foo *)malloc(bytes))[0 .. 10];
GC.addRange(ptrs.ptr, bytes);
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