// SPDX-License-Identifier: Apache-2.0 OR MIT //! Memory allocation APIs #![stable(feature = "alloc_module", since = "1.28.0")] #[cfg(not(test))]use core::intrinsics; #[cfg(not(test))]use core::ptr::{self, NonNull}; #[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 to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute    // (the code expanding that attribute macro generates those functions), or to call    // the default implementations in std (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)    // otherwise.    // The rustc fork of LLVM 14 and earlier also special-cases these function names to be able to optimize them    // like `malloc`, `realloc`, and `free`, respectively.    #[rustc_allocator]    #[rustc_nounwind]    fn __rust_alloc(size: usize, align: usize) -> *mut u8;    #[rustc_deallocator]    #[rustc_nounwind]    fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);    #[rustc_reallocator]    #[rustc_nounwind]    fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;    #[rustc_allocator_zeroed]    #[rustc_nounwind]    fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;     static __rust_no_alloc_shim_is_unstable: u8;} /// The global memory allocator.////// This type implements the [`Allocator`] 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`](self#functions).#[unstable(feature = "allocator_api", issue = "32838")]#[derive(Copy, Clone, Default, Debug)]#[cfg(not(test))]pub struct Global; #[cfg(test)]pub use std::alloc::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 [`Allocator`] trait become stable.////// # Safety////// See [`GlobalAlloc::alloc`].////// # Examples////// ```/// use std::alloc::{alloc, dealloc, handle_alloc_error, Layout};////// unsafe {///     let layout = Layout::new::<u16>();///     let ptr = alloc(layout);///     if ptr.is_null() {///         handle_alloc_error(layout);///     }//////     *(ptr as *mut u16) = 42;///     assert_eq!(*(ptr as *mut u16), 42);//////     dealloc(ptr, layout);/// }/// ```#[stable(feature = "global_alloc", since = "1.28.0")]#[must_use = "losing the pointer will leak memory"]#[inline]pub unsafe fn alloc(layout: Layout) -> *mut u8 {    unsafe {        // Make sure we don't accidentally allow omitting the allocator shim in        // stable code until it is actually stabilized.        core::ptr::read_volatile(&__rust_no_alloc_shim_is_unstable);         __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 [`Allocator`] trait become stable.////// # Safety////// See [`GlobalAlloc::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 [`Allocator`] trait become stable.////// # Safety////// See [`GlobalAlloc::realloc`].#[stable(feature = "global_alloc", since = "1.28.0")]#[must_use = "losing the pointer will leak memory"]#[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 [`Allocator`] trait become stable.////// # Safety////// See [`GlobalAlloc::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")]#[must_use = "losing the pointer will leak memory"]#[inline]pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {    unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }} #[cfg(not(test))]impl Global {    #[inline]    fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {        match layout.size() {            0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),            // SAFETY: `layout` is non-zero in size,            size => unsafe {                let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };                let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;                Ok(NonNull::slice_from_raw_parts(ptr, size))            },        }    }     // SAFETY: Same as `Allocator::grow`    #[inline]    unsafe fn grow_impl(        &self,        ptr: NonNull<u8>,        old_layout: Layout,        new_layout: Layout,        zeroed: bool,    ) -> Result<NonNull<[u8]>, AllocError> {        debug_assert!(            new_layout.size() >= old_layout.size(),            "`new_layout.size()` must be greater than or equal to `old_layout.size()`"        );         match old_layout.size() {            0 => self.alloc_impl(new_layout, zeroed),             // SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`            // as required by safety conditions. Other conditions must be upheld by the caller            old_size if old_layout.align() == new_layout.align() => unsafe {                let new_size = new_layout.size();                 // `realloc` probably checks for `new_size >= old_layout.size()` or something similar.                intrinsics::assume(new_size >= old_layout.size());                 let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);                let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;                if zeroed {                    raw_ptr.add(old_size).write_bytes(0, new_size - old_size);                }                Ok(NonNull::slice_from_raw_parts(ptr, new_size))            },             // SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,            // both the old and new memory allocation are valid for reads and writes for `old_size`            // bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap            // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract            // for `dealloc` must be upheld by the caller.            old_size => unsafe {                let new_ptr = self.alloc_impl(new_layout, zeroed)?;                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);                self.deallocate(ptr, old_layout);                Ok(new_ptr)            },        }    }} #[unstable(feature = "allocator_api", issue = "32838")]#[cfg(not(test))]unsafe impl Allocator for Global {    #[inline]    fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {        self.alloc_impl(layout, false)    }     #[inline]    fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {        self.alloc_impl(layout, true)    }     #[inline]    unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {        if layout.size() != 0 {            // SAFETY: `layout` is non-zero in size,            // other conditions must be upheld by the caller            unsafe { dealloc(ptr.as_ptr(), layout) }        }    }     #[inline]    unsafe fn grow(        &self,        ptr: NonNull<u8>,        old_layout: Layout,        new_layout: Layout,    ) -> Result<NonNull<[u8]>, AllocError> {        // SAFETY: all conditions must be upheld by the caller        unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }    }     #[inline]    unsafe fn grow_zeroed(        &self,        ptr: NonNull<u8>,        old_layout: Layout,        new_layout: Layout,    ) -> Result<NonNull<[u8]>, AllocError> {        // SAFETY: all conditions must be upheld by the caller        unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }    }     #[inline]    unsafe fn shrink(        &self,        ptr: NonNull<u8>,        old_layout: Layout,        new_layout: Layout,    ) -> Result<NonNull<[u8]>, AllocError> {        debug_assert!(            new_layout.size() <= old_layout.size(),            "`new_layout.size()` must be smaller than or equal to `old_layout.size()`"        );         match new_layout.size() {            // SAFETY: conditions must be upheld by the caller            0 => unsafe {                self.deallocate(ptr, old_layout);                Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))            },             // SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller            new_size if old_layout.align() == new_layout.align() => unsafe {                // `realloc` probably checks for `new_size <= old_layout.size()` or something similar.                intrinsics::assume(new_size <= old_layout.size());                 let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);                let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;                Ok(NonNull::slice_from_raw_parts(ptr, new_size))            },             // SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,            // both the old and new memory allocation are valid for reads and writes for `new_size`            // bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap            // `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract            // for `dealloc` must be upheld by the caller.            new_size => unsafe {                let new_ptr = self.allocate(new_layout)?;                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);                self.deallocate(ptr, old_layout);                Ok(new_ptr)            },        }    }} /// The allocator for unique pointers.#[cfg(all(not(no_global_oom_handling), 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.allocate(layout) {        Ok(ptr) => ptr.as_mut_ptr(),        Err(_) => handle_alloc_error(layout),    }} // # Allocation error handler #[cfg(not(no_global_oom_handling))]extern "Rust" {    // This is the magic symbol to call the global alloc error handler. rustc generates    // it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the    // default implementations below (`__rdl_oom`) otherwise.    fn __rust_alloc_error_handler(size: usize, align: usize) -> !;} /// Signal a memory allocation error.////// Callers of memory allocation APIs wishing to cease execution/// in response to an allocation error are encouraged to call this function,/// rather than directly invoking [`panic!`] or similar.////// This function is guaranteed to diverge (not return normally with a value), but depending on/// global configuration, it may either panic (resulting in unwinding or aborting as per/// configuration for all panics), or abort the process (with no unwinding).////// The default behavior is://////  * If the binary links against `std` (typically the case), then///   print a message to standard error and abort the process.///   This behavior can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].///   Future versions of Rust may panic by default instead.////// * If the binary does not link against `std` (all of its crates are marked///   [`#![no_std]`][no_std]), then call [`panic!`] with a message.///   [The panic handler] applies as to any panic.////// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html/// [The panic handler]: https://doc.rust-lang.org/reference/runtime.html#the-panic_handler-attribute/// [no_std]: https://doc.rust-lang.org/reference/names/preludes.html#the-no_std-attribute#[stable(feature = "global_alloc", since = "1.28.0")]#[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]#[cfg(all(not(no_global_oom_handling), not(test)))]#[cold]pub const fn handle_alloc_error(layout: Layout) -> ! {    const fn ct_error(_: Layout) -> ! {        panic!("allocation failed");    }     #[inline]    fn rt_error(layout: Layout) -> ! {        unsafe {            __rust_alloc_error_handler(layout.size(), layout.align());        }    }     #[cfg(not(feature = "panic_immediate_abort"))]    unsafe {        core::intrinsics::const_eval_select((layout,), ct_error, rt_error)    }     #[cfg(feature = "panic_immediate_abort")]    ct_error(layout)} // For alloc test `std::alloc::handle_alloc_error` can be used directly.#[cfg(all(not(no_global_oom_handling), test))]pub use std::alloc::handle_alloc_error; #[cfg(all(not(no_global_oom_handling), not(test)))]#[doc(hidden)]#[allow(unused_attributes)]#[unstable(feature = "alloc_internals", issue = "none")]pub mod __alloc_error_handler {    // called via generated `__rust_alloc_error_handler` if there is no    // `#[alloc_error_handler]`.    #[rustc_std_internal_symbol]    pub unsafe fn __rdl_oom(size: usize, _align: usize) -> ! {        extern "Rust" {            // This symbol is emitted by rustc next to __rust_alloc_error_handler.            // Its value depends on the -Zoom={panic,abort} compiler option.            static __rust_alloc_error_handler_should_panic: u8;        }         if unsafe { __rust_alloc_error_handler_should_panic != 0 } {            panic!("memory allocation of {size} bytes failed")        } else {            core::panicking::panic_nounwind_fmt(                format_args!("memory allocation of {size} bytes failed"),                /* force_no_backtrace */ false,            )        }    }} #[cfg(not(no_global_oom_handling))]/// Specialize clones into pre-allocated, uninitialized memory./// Used by `Box::clone` and `Rc`/`Arc::make_mut`.pub(crate) trait WriteCloneIntoRaw: Sized {    unsafe fn write_clone_into_raw(&self, target: *mut Self);} #[cfg(not(no_global_oom_handling))]impl<T: Clone> WriteCloneIntoRaw for T {    #[inline]    default unsafe fn write_clone_into_raw(&self, target: *mut Self) {        // Having allocated *first* may allow the optimizer to create        // the cloned value in-place, skipping the local and move.        unsafe { target.write(self.clone()) };    }} #[cfg(not(no_global_oom_handling))]impl<T: Copy> WriteCloneIntoRaw for T {    #[inline]    unsafe fn write_clone_into_raw(&self, target: *mut Self) {        // We can always copy in-place, without ever involving a local value.        unsafe { target.copy_from_nonoverlapping(self, 1) };    }}