On Friday, 8 September 2023 at 07:59:37 UTC, rempas wrote:
I do have the following struct:
```d
struct Vec(T) {
private:
T* _ptr = null; // The pointer to the data
u64 _cap = 0; // Total amount of elements (not bytes) we
can store
public:
/* Create a vector by just allocating memory for it. The null
terminator is not set for
strings as, the vector is considered empty and we should
first push something to it
in order to use it! */
this(i64 size) {
this._len = 0;
this._cap = size;
static if (is(T == char)) { size += 1; } // Additional
space for the null terminator
this._ptr = cast(T*)malloc(size);
}
}
```
That's some minimal code that I do have just to showcase it.
So, some times, this work will works, some others, it will give
me the following error:
`Fatal glibc error: malloc.c:2594 (sysmalloc): assertion
failed: (old_top == initial_top (av) && old_size == 0) ||
((unsigned long) (old_size) >= MINSIZE && prev_inuse (old_top)
&& ((unsigned long) old_end & (pagesize - 1)) == 0)`
The problem seems to happen when the pointer that is returned
from `malloc` is assigned to the `_ptr` field. If I just assign
it to a variable and don't assign anything to `_ptr`, it will
work!
Is there any possible that there is a compiler bug? I do use
ldc2 and `betterC`!
Hello, not completely unrelated to your problem, I have also done
something like that, and when you're in D, don't use simply a
pointer and length like that, use the `slice` operator.
See references:
https://tour.dlang.org/tour/en/basics/slices
https://dlang.org/spec/operatoroverloading.html#array-ops
For example, you can make your pointer a lot safer by doing:
```d
size_t length = 5;
int* pointer = cast(int*)malloc(int.sizeof * length); //Don't
int[] mallocArray = (cast(int*)malloc(int.sizeof *
length))[0..length]; //Do
```
On the second way, you'll get bound checks, thus, making it
safer. Also, no need to keep track of your length separately
anymore.
This is good practice in D language and you'll find yourself
using this instead in the future.
And yes, this works in betterC, it is a simple runtime check,
completely `@nogc @safe nothrow` and every other kind of thing
you would want.
