alloc.rs.html -- source
Description: Source to the Rust file `libstd/alloc.rs`.
Keywords: rust, rustlang, rust-lang

      1
      2
      3
      4
      5
      6
      7
      8
      9
     10
     11
     12
     13
     14
     15
     16
     17
     18
     19
     20
     21
     22
     23
     24
     25
     26
     27
     28
     29
     30
     31
     32
     33
     34
     35
     36
     37
     38
     39
     40
     41
     42
     43
     44
     45
     46
     47
     48
     49
     50
     51
     52
     53
     54
     55
     56
     57
     58
     59
     60
     61
     62
     63
     64
     65
     66
     67
     68
     69
     70
     71
     72
     73
     74
     75
     76
     77
     78
     79
     80
     81
     82
     83
     84
     85
     86
     87
     88
     89
     90
     91
     92
     93
     94
     95
     96
     97
     98
     99
    100
    101
    102
    103
    104
    105
    106
    107
    108
    109
    110
    111
    112
    113
    114
    115
    116
    117
    118
    119
    120
    121
    122
    123
    124
    125
    126
    127
    128
    129
    130
    131
    132
    133
    134
    135
    136
    137
    138
    139
    140
    141
    142
    143
    144
    145
    146
    147
    148
    149
    150
    151
    152
    153
    154
    155
    156
    157
    158
    159
    160
    161
    162
    163
    164
    165
    166
    167
    168
    169
    170
    171
    172
    173
    174
    175
    176
    177
    178
    179
    180
    181
    182
    183
    184
    185

    // Copyright 2017 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    //! Memory allocation APIs
    //!
    //! In a given program, the standard library has one “global” memory allocator
    //! that is used for example by `Box<T>` and `Vec<T>`.
    //!
    //! Currently the default global allocator is unspecified.
    //! The compiler may link to a version of [jemalloc] on some platforms,
    //! but this is not guaranteed.
    //! Libraries, however, like `cdylib`s and `staticlib`s are guaranteed
    //! to use the [`System`] by default.
    //!
    //! [jemalloc]: https://github.com/jemalloc/jemalloc
    //! [`System`]: struct.System.html
    //!
    //! # The `#[global_allocator]` attribute
    //!
    //! This attribute allows configuring the choice of global allocator.
    //! You can use this to implement a completely custom global allocator
    //! to route all default allocation requests to a custom object.
    //!
    //! ```rust
    //! use std::alloc::{GlobalAlloc, System, Layout};
    //!
    //! struct MyAllocator;
    //!
    //! unsafe impl GlobalAlloc for MyAllocator {
    //!     unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
    //!         System.alloc(layout)
    //!     }
    //!
    //!     unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
    //!         System.dealloc(ptr, layout)
    //!     }
    //! }
    //!
    //! #[global_allocator]
    //! static GLOBAL: MyAllocator = MyAllocator;
    //!
    //! fn main() {
    //!     // This `Vec` will allocate memory through `GLOBAL` above
    //!     let mut v = Vec::new();
    //!     v.push(1);
    //! }
    //! ```
    //!
    //! The attribute is used on a `static` item whose type implements the
    //! [`GlobalAlloc`] trait. This type can be provided by an external library:
    //!
    //! [`GlobalAlloc`]: ../../core/alloc/trait.GlobalAlloc.html
    //!
    //! ```rust,ignore (demonstrates crates.io usage)
    //! extern crate jemallocator;
    //!
    //! use jemallocator::Jemalloc;
    //!
    //! #[global_allocator]
    //! static GLOBAL: Jemalloc = Jemalloc;
    //!
    //! fn main() {}
    //! ```
    //!
    //! The `#[global_allocator]` can only be used once in a crate
    //! or its recursive dependencies.

    #![stable(feature = "alloc_module", since = "1.28.0")]

    use core::sync::atomic::{AtomicPtr, Ordering};
    use core::{mem, ptr};
    use sys_common::util::dumb_print;

    #[stable(feature = "alloc_module", since = "1.28.0")]
    #[doc(inline)]
    pub use alloc_crate::alloc::*;

    #[stable(feature = "alloc_system_type", since = "1.28.0")]
    #[doc(inline)]
    pub use alloc_system::System;

    static HOOK: AtomicPtr<()> = AtomicPtr::new(ptr::null_mut());

    /// Registers a custom allocation error hook, replacing any that was previously registered.
    ///
    /// The allocation error hook is invoked when an infallible memory allocation fails, before
    /// the runtime aborts. The default hook prints a message to standard error,
    /// but this behavior can be customized with the [`set_alloc_error_hook`] and
    /// [`take_alloc_error_hook`] functions.
    ///
    /// The hook is provided with a `Layout` struct which contains information
    /// about the allocation that failed.
    ///
    /// The allocation error hook is a global resource.
    #[unstable(feature = "alloc_error_hook", issue = "51245")]
    pub fn set_alloc_error_hook(hook: fn(Layout)) {
        HOOK.store(hook as *mut (), Ordering::SeqCst);
    }

    /// Unregisters the current allocation error hook, returning it.
    ///
    /// *See also the function [`set_alloc_error_hook`].*
    ///
    /// If no custom hook is registered, the default hook will be returned.
    #[unstable(feature = "alloc_error_hook", issue = "51245")]
    pub fn take_alloc_error_hook() -> fn(Layout) {
        let hook = HOOK.swap(ptr::null_mut(), Ordering::SeqCst);
        if hook.is_null() {
            default_alloc_error_hook
        } else {
            unsafe { mem::transmute(hook) }
        }
    }

    fn default_alloc_error_hook(layout: Layout) {
        dumb_print(format_args!("memory allocation of {} bytes failed", layout.size()));
    }

    #[cfg(not(test))]
    #[doc(hidden)]
    #[cfg_attr(stage0, lang = "oom")]
    #[cfg_attr(not(stage0), alloc_error_handler)]
    #[unstable(feature = "alloc_internals", issue = "0")]
    pub fn rust_oom(layout: Layout) -> ! {
        let hook = HOOK.load(Ordering::SeqCst);
        let hook: fn(Layout) = if hook.is_null() {
            default_alloc_error_hook
        } else {
            unsafe { mem::transmute(hook) }
        };
        hook(layout);
        unsafe { ::sys::abort_internal(); }
    }

    #[cfg(not(test))]
    #[doc(hidden)]
    #[allow(unused_attributes)]
    #[unstable(feature = "alloc_internals", issue = "0")]
    pub mod __default_lib_allocator {
        use super::{System, Layout, GlobalAlloc};
        // for symbol names src/librustc/middle/allocator.rs
        // for signatures src/librustc_allocator/lib.rs

        // linkage directives are provided as part of the current compiler allocator
        // ABI

        #[no_mangle]
        #[rustc_std_internal_symbol]
        pub unsafe extern fn __rdl_alloc(size: usize, align: usize) -> *mut u8 {
            let layout = Layout::from_size_align_unchecked(size, align);
            System.alloc(layout)
        }

        #[no_mangle]
        #[rustc_std_internal_symbol]
        pub unsafe extern fn __rdl_dealloc(ptr: *mut u8,
                                           size: usize,
                                           align: usize) {
            System.dealloc(ptr, Layout::from_size_align_unchecked(size, align))
        }

        #[no_mangle]
        #[rustc_std_internal_symbol]
        pub unsafe extern fn __rdl_realloc(ptr: *mut u8,
                                           old_size: usize,
                                           align: usize,
                                           new_size: usize) -> *mut u8 {
            let old_layout = Layout::from_size_align_unchecked(old_size, align);
            System.realloc(ptr, old_layout, new_size)
        }

        #[no_mangle]
        #[rustc_std_internal_symbol]
        pub unsafe extern fn __rdl_alloc_zeroed(size: usize, align: usize) -> *mut u8 {
            let layout = Layout::from_size_align_unchecked(size, align);
            System.alloc_zeroed(layout)
        }
    }

# Help

## Keyboard Shortcuts

`?`
  Show this help dialog
`S`
  Focus the search field
`↑`
  Move up in search results
`↓`
  Move down in search results
`↹`
  Switch tab
`⏎`
  Go to active search result
`+`
  Expand all sections
`-`
  Collapse all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)

Search multiple things at once by splitting your query with comma (e.g. `str,u8` or `String,struct:Vec,test`)