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Diffstat (limited to 'library/alloc/src/alloc.rs')
| -rw-r--r-- | library/alloc/src/alloc.rs | 319 |
1 files changed, 319 insertions, 0 deletions
diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs new file mode 100644 index 00000000000..98c7ac3f2ef --- /dev/null +++ b/library/alloc/src/alloc.rs @@ -0,0 +1,319 @@ +//! Memory allocation APIs + +#![stable(feature = "alloc_module", since = "1.28.0")] + +use core::intrinsics::{self, min_align_of_val, size_of_val}; +use core::ptr::{NonNull, Unique}; + +#[stable(feature = "alloc_module", since = "1.28.0")] +#[doc(inline)] +pub use core::alloc::*; + +#[cfg(test)] +mod tests; + +extern "Rust" { + // These are the magic symbols to call the global allocator. rustc generates + // them from the `#[global_allocator]` attribute if there is one, or uses the + // default implementations in libstd (`__rdl_alloc` etc in `src/libstd/alloc.rs`) + // otherwise. + #[rustc_allocator] + #[rustc_allocator_nounwind] + fn __rust_alloc(size: usize, align: usize) -> *mut u8; + #[rustc_allocator_nounwind] + fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize); + #[rustc_allocator_nounwind] + fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8; + #[rustc_allocator_nounwind] + fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8; +} + +/// The global memory allocator. +/// +/// This type implements the [`AllocRef`] trait by forwarding calls +/// to the allocator registered with the `#[global_allocator]` attribute +/// if there is one, or the `std` crate’s default. +/// +/// Note: while this type is unstable, the functionality it provides can be +/// accessed through the [free functions in `alloc`](index.html#functions). +/// +/// [`AllocRef`]: trait.AllocRef.html +#[unstable(feature = "allocator_api", issue = "32838")] +#[derive(Copy, Clone, Default, Debug)] +pub struct Global; + +/// Allocate memory with the global allocator. +/// +/// This function forwards calls to the [`GlobalAlloc::alloc`] method +/// of the allocator registered with the `#[global_allocator]` attribute +/// if there is one, or the `std` crate’s default. +/// +/// This function is expected to be deprecated in favor of the `alloc` method +/// of the [`Global`] type when it and the [`AllocRef`] trait become stable. +/// +/// # Safety +/// +/// See [`GlobalAlloc::alloc`]. +/// +/// [`Global`]: struct.Global.html +/// [`AllocRef`]: trait.AllocRef.html +/// [`GlobalAlloc::alloc`]: trait.GlobalAlloc.html#tymethod.alloc +/// +/// # Examples +/// +/// ``` +/// use std::alloc::{alloc, dealloc, Layout}; +/// +/// unsafe { +/// let layout = Layout::new::<u16>(); +/// let ptr = alloc(layout); +/// +/// *(ptr as *mut u16) = 42; +/// assert_eq!(*(ptr as *mut u16), 42); +/// +/// dealloc(ptr, layout); +/// } +/// ``` +#[stable(feature = "global_alloc", since = "1.28.0")] +#[inline] +pub unsafe fn alloc(layout: Layout) -> *mut u8 { + unsafe { __rust_alloc(layout.size(), layout.align()) } +} + +/// Deallocate memory with the global allocator. +/// +/// This function forwards calls to the [`GlobalAlloc::dealloc`] method +/// of the allocator registered with the `#[global_allocator]` attribute +/// if there is one, or the `std` crate’s default. +/// +/// This function is expected to be deprecated in favor of the `dealloc` method +/// of the [`Global`] type when it and the [`AllocRef`] trait become stable. +/// +/// # Safety +/// +/// See [`GlobalAlloc::dealloc`]. +/// +/// [`Global`]: struct.Global.html +/// [`AllocRef`]: trait.AllocRef.html +/// [`GlobalAlloc::dealloc`]: trait.GlobalAlloc.html#tymethod.dealloc +#[stable(feature = "global_alloc", since = "1.28.0")] +#[inline] +pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) { + unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) } +} + +/// Reallocate memory with the global allocator. +/// +/// This function forwards calls to the [`GlobalAlloc::realloc`] method +/// of the allocator registered with the `#[global_allocator]` attribute +/// if there is one, or the `std` crate’s default. +/// +/// This function is expected to be deprecated in favor of the `realloc` method +/// of the [`Global`] type when it and the [`AllocRef`] trait become stable. +/// +/// # Safety +/// +/// See [`GlobalAlloc::realloc`]. +/// +/// [`Global`]: struct.Global.html +/// [`AllocRef`]: trait.AllocRef.html +/// [`GlobalAlloc::realloc`]: trait.GlobalAlloc.html#method.realloc +#[stable(feature = "global_alloc", since = "1.28.0")] +#[inline] +pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 { + unsafe { __rust_realloc(ptr, layout.size(), layout.align(), new_size) } +} + +/// Allocate zero-initialized memory with the global allocator. +/// +/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method +/// of the allocator registered with the `#[global_allocator]` attribute +/// if there is one, or the `std` crate’s default. +/// +/// This function is expected to be deprecated in favor of the `alloc_zeroed` method +/// of the [`Global`] type when it and the [`AllocRef`] trait become stable. +/// +/// # Safety +/// +/// See [`GlobalAlloc::alloc_zeroed`]. +/// +/// [`Global`]: struct.Global.html +/// [`AllocRef`]: trait.AllocRef.html +/// [`GlobalAlloc::alloc_zeroed`]: trait.GlobalAlloc.html#method.alloc_zeroed +/// +/// # Examples +/// +/// ``` +/// use std::alloc::{alloc_zeroed, dealloc, Layout}; +/// +/// unsafe { +/// let layout = Layout::new::<u16>(); +/// let ptr = alloc_zeroed(layout); +/// +/// assert_eq!(*(ptr as *mut u16), 0); +/// +/// dealloc(ptr, layout); +/// } +/// ``` +#[stable(feature = "global_alloc", since = "1.28.0")] +#[inline] +pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 { + unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) } +} + +#[unstable(feature = "allocator_api", issue = "32838")] +unsafe impl AllocRef for Global { + #[inline] + fn alloc(&mut self, layout: Layout, init: AllocInit) -> Result<MemoryBlock, AllocErr> { + unsafe { + let size = layout.size(); + if size == 0 { + Ok(MemoryBlock { ptr: layout.dangling(), size: 0 }) + } else { + let raw_ptr = match init { + AllocInit::Uninitialized => alloc(layout), + AllocInit::Zeroed => alloc_zeroed(layout), + }; + let ptr = NonNull::new(raw_ptr).ok_or(AllocErr)?; + Ok(MemoryBlock { ptr, size }) + } + } + } + + #[inline] + unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) { + if layout.size() != 0 { + unsafe { dealloc(ptr.as_ptr(), layout) } + } + } + + #[inline] + unsafe fn grow( + &mut self, + ptr: NonNull<u8>, + layout: Layout, + new_size: usize, + placement: ReallocPlacement, + init: AllocInit, + ) -> Result<MemoryBlock, AllocErr> { + let size = layout.size(); + debug_assert!( + new_size >= size, + "`new_size` must be greater than or equal to `memory.size()`" + ); + + if size == new_size { + return Ok(MemoryBlock { ptr, size }); + } + + match placement { + ReallocPlacement::InPlace => Err(AllocErr), + ReallocPlacement::MayMove if layout.size() == 0 => { + let new_layout = + unsafe { Layout::from_size_align_unchecked(new_size, layout.align()) }; + self.alloc(new_layout, init) + } + ReallocPlacement::MayMove => { + // `realloc` probably checks for `new_size > size` or something similar. + let ptr = unsafe { + intrinsics::assume(new_size > size); + realloc(ptr.as_ptr(), layout, new_size) + }; + let memory = + MemoryBlock { ptr: NonNull::new(ptr).ok_or(AllocErr)?, size: new_size }; + unsafe { + init.init_offset(memory, size); + } + Ok(memory) + } + } + } + + #[inline] + unsafe fn shrink( + &mut self, + ptr: NonNull<u8>, + layout: Layout, + new_size: usize, + placement: ReallocPlacement, + ) -> Result<MemoryBlock, AllocErr> { + let size = layout.size(); + debug_assert!( + new_size <= size, + "`new_size` must be smaller than or equal to `memory.size()`" + ); + + if size == new_size { + return Ok(MemoryBlock { ptr, size }); + } + + match placement { + ReallocPlacement::InPlace => Err(AllocErr), + ReallocPlacement::MayMove if new_size == 0 => { + unsafe { + self.dealloc(ptr, layout); + } + Ok(MemoryBlock { ptr: layout.dangling(), size: 0 }) + } + ReallocPlacement::MayMove => { + // `realloc` probably checks for `new_size < size` or something similar. + let ptr = unsafe { + intrinsics::assume(new_size < size); + realloc(ptr.as_ptr(), layout, new_size) + }; + Ok(MemoryBlock { ptr: NonNull::new(ptr).ok_or(AllocErr)?, size: new_size }) + } + } + } +} + +/// The allocator for unique pointers. +// This function must not unwind. If it does, MIR codegen will fail. +#[cfg(not(test))] +#[lang = "exchange_malloc"] +#[inline] +unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 { + let layout = unsafe { Layout::from_size_align_unchecked(size, align) }; + match Global.alloc(layout, AllocInit::Uninitialized) { + Ok(memory) => memory.ptr.as_ptr(), + Err(_) => handle_alloc_error(layout), + } +} + +#[cfg_attr(not(test), lang = "box_free")] +#[inline] +// This signature has to be the same as `Box`, otherwise an ICE will happen. +// When an additional parameter to `Box` is added (like `A: AllocRef`), this has to be added here as +// well. +// For example if `Box` is changed to `struct Box<T: ?Sized, A: AllocRef>(Unique<T>, A)`, +// this function has to be changed to `fn box_free<T: ?Sized, A: AllocRef>(Unique<T>, A)` as well. +pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) { + unsafe { + let size = size_of_val(ptr.as_ref()); + let align = min_align_of_val(ptr.as_ref()); + let layout = Layout::from_size_align_unchecked(size, align); + Global.dealloc(ptr.cast().into(), layout) + } +} + +/// Abort on memory allocation error or failure. +/// +/// Callers of memory allocation APIs wishing to abort computation +/// in response to an allocation error are encouraged to call this function, +/// rather than directly invoking `panic!` or similar. +/// +/// The default behavior of this function is to print a message to standard error +/// and abort the process. +/// It can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`]. +/// +/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html +/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html +#[stable(feature = "global_alloc", since = "1.28.0")] +#[rustc_allocator_nounwind] +pub fn handle_alloc_error(layout: Layout) -> ! { + extern "Rust" { + #[lang = "oom"] + fn oom_impl(layout: Layout) -> !; + } + unsafe { oom_impl(layout) } +} |