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Add missing unsafe

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Philipp Oppermann
2017-04-18 14:58:52 +02:00
parent 538cc32766
commit f5d9766868
1 changed files with 9 additions and 5 deletions
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14
blog/content/post/08-kernel-heap.md
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@@ -715,7 +715,9 @@ extern crate linked_list_allocator;
pub const HEAP_START: usize = 0o_000_001_000_000_0000; pub const HEAP_START: usize = 0o_000_001_000_000_0000;
pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB pub const HEAP_SIZE: usize = 100 * 1024; // 100 KiB
static HEAP: Mutex<Heap> = Mutex::new(Heap::new(HEAP_START, HEAP_SIZE)); static HEAP: Mutex<Heap> = Mutex::new(unsafe {
Heap::new(HEAP_START, HEAP_SIZE)
});
``` ```
Note that we use the same values for `HEAP_START` and `HEAP_SIZE` as in the `bump_allocator`. Note that we use the same values for `HEAP_START` and `HEAP_SIZE` as in the `bump_allocator`.
@@ -729,10 +731,12 @@ We need to add the extern crates to our `Cargo.toml`:
However, we get an error when we try to compile it: However, we get an error when we try to compile it:
``` ```
error: function calls in statics are limited to constant functions, error[E0015]: calls in statics are limited to constant functions,
struct and enum constructors [E0015] struct and enum constructors
static HEAP: Mutex<Heap> = Mutex::new(Heap::new(HEAP_START, HEAP_SIZE)); --> src/lib.rs:17:5
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
17 | Heap::new(HEAP_START, HEAP_SIZE)
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
``` ```
The reason is that the `Heap::new` function needs to initialize the first hole (like described [above](#initialization)). This can't be done at compile time, so the function can't be a `const` function. Therefore we can't use it to initialize a static. The reason is that the `Heap::new` function needs to initialize the first hole (like described [above](#initialization)). This can't be done at compile time, so the function can't be a `const` function. Therefore we can't use it to initialize a static.