Global.oom -> heap::alloc::oom and explanation fixup

pull/66/head
Alexis Beingessner 7 years ago
parent 9bd87c10a2
commit 23e4f08171

@ -37,10 +37,11 @@ that, we'll need to use the rest of the heap APIs. These basically allow us to
talk directly to Rust's allocator (jemalloc by default). talk directly to Rust's allocator (jemalloc by default).
We'll also need a way to handle out-of-memory (OOM) conditions. The standard We'll also need a way to handle out-of-memory (OOM) conditions. The standard
library calls the `abort` intrinsic, which just calls an illegal instruction to library calls `std::alloc::oom()`, which in turn calls the the `oom` langitem.
crash the whole program. The reason we abort and don't panic is because By default this just aborts the program by executing an illegal cpu instruction.
unwinding can cause allocations to happen, and that seems like a bad thing to do The reason we abort and don't panic is because unwinding can cause allocations
when your allocator just came back with "hey I don't have any more memory". to happen, and that seems like a bad thing to do when your allocator just came
back with "hey I don't have any more memory".
Of course, this is a bit silly since most platforms don't actually run out of Of course, this is a bit silly since most platforms don't actually run out of
memory in a conventional way. Your operating system will probably kill the memory in a conventional way. Your operating system will probably kill the
@ -51,15 +52,6 @@ of memory at once (e.g. half the theoretical address space). As such it's
like the standard library as much as possible, so we'll just kill the whole like the standard library as much as possible, so we'll just kill the whole
program. program.
We said we don't want to use intrinsics, so doing exactly what `std` does is
out. Instead, we'll call `std::process::exit` with some random number.
```rust
fn oom() {
::std::process::exit(-9999);
}
```
Okay, now we can write growing. Roughly, we want to have this logic: Okay, now we can write growing. Roughly, we want to have this logic:
```text ```text
@ -165,6 +157,8 @@ such we will guard against this case explicitly.
Ok with all the nonsense out of the way, let's actually allocate some memory: Ok with all the nonsense out of the way, let's actually allocate some memory:
```rust,ignore ```rust,ignore
use std::alloc::oom;
fn grow(&mut self) { fn grow(&mut self) {
// this is all pretty delicate, so let's say it's all unsafe // this is all pretty delicate, so let's say it's all unsafe
unsafe { unsafe {

@ -9,7 +9,7 @@ use std::ptr::{Unique, self};
use std::mem; use std::mem;
use std::ops::{Deref, DerefMut}; use std::ops::{Deref, DerefMut};
use std::marker::PhantomData; use std::marker::PhantomData;
use std::alloc::{GlobalAlloc, Layout, Global}; use std::alloc::{GlobalAlloc, Layout, Global, oom};
struct RawVec<T> { struct RawVec<T> {
ptr: Unique<T>, ptr: Unique<T>,
@ -46,7 +46,7 @@ impl<T> RawVec<T> {
// If allocate or reallocate fail, oom // If allocate or reallocate fail, oom
if ptr.is_null() { if ptr.is_null() {
Global.oom() oom()
} }
self.ptr = Unique::new_unchecked(ptr as *mut _); self.ptr = Unique::new_unchecked(ptr as *mut _);
@ -299,12 +299,5 @@ impl<'a, T> Drop for Drain<'a, T> {
} }
} }
/// Abort the process, we're out of memory!
///
/// In practice this is probably dead code on most OSes
fn oom() {
::std::process::exit(-9999);
}
# fn main() {} # fn main() {}
``` ```

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