Re: Antipattern in core.memory.GC.addRange?
On 9/23/17 1:55 AM, Petar Kirov [ZombineDev] wrote:
How about adding a template wrapper function, along the lines of:
static void addRange(T)(const T[] arr)
{
addRange(arr.ptr, T.sizeof * arr.length, typeid(T));
}
To core.memory.GC?
It sounds good. But will it be accepted?
Note, the true implementation should use integer overflow to reject
invalid arrays.
-Steve
Re: Antipattern in core.memory.GC.addRange?
On 9/23/17 1:30 AM, safety0ff wrote:
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);
Right, the problem is that the API accepts this without error, because
of the implicit cast to void *.
The simple rule should be that if we can prevent something obviously
wrong from compiling, we should do so.
-Steve
Re: Antipattern in core.memory.GC.addRange?
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? Why would addRange work this way, when D has
such a better mechanism for this? Can we fix it?
-Steve
How about adding a template wrapper function, along the lines of:
static void addRange(T)(const T[] arr)
{
addRange(arr.ptr, T.sizeof * arr.length, typeid(T));
}
To core.memory.GC?
Re: Antipattern in core.memory.GC.addRange?
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);
