Re: Antipattern in core.memory.GC.addRange?

[safety0ff via Digitalmars-d]

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);