diff options
Diffstat (limited to 'library/std/src/sys/unix/alloc.rs')
| -rw-r--r-- | library/std/src/sys/unix/alloc.rs | 101 |
1 files changed, 101 insertions, 0 deletions
diff --git a/library/std/src/sys/unix/alloc.rs b/library/std/src/sys/unix/alloc.rs new file mode 100644 index 000000000..9d6567c9f --- /dev/null +++ b/library/std/src/sys/unix/alloc.rs @@ -0,0 +1,101 @@ +use crate::alloc::{GlobalAlloc, Layout, System}; +use crate::ptr; +use crate::sys::common::alloc::{realloc_fallback, MIN_ALIGN}; + +#[stable(feature = "alloc_system_type", since = "1.28.0")] +unsafe impl GlobalAlloc for System { + #[inline] + unsafe fn alloc(&self, layout: Layout) -> *mut u8 { + // jemalloc provides alignment less than MIN_ALIGN for small allocations. + // So only rely on MIN_ALIGN if size >= align. + // Also see <https://github.com/rust-lang/rust/issues/45955> and + // <https://github.com/rust-lang/rust/issues/62251#issuecomment-507580914>. + if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() { + libc::malloc(layout.size()) as *mut u8 + } else { + #[cfg(target_os = "macos")] + { + if layout.align() > (1 << 31) { + return ptr::null_mut(); + } + } + aligned_malloc(&layout) + } + } + + #[inline] + unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 { + // See the comment above in `alloc` for why this check looks the way it does. + if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() { + libc::calloc(layout.size(), 1) as *mut u8 + } else { + let ptr = self.alloc(layout); + if !ptr.is_null() { + ptr::write_bytes(ptr, 0, layout.size()); + } + ptr + } + } + + #[inline] + unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) { + libc::free(ptr as *mut libc::c_void) + } + + #[inline] + unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 { + if layout.align() <= MIN_ALIGN && layout.align() <= new_size { + libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8 + } else { + realloc_fallback(self, ptr, layout, new_size) + } + } +} + +cfg_if::cfg_if! { + if #[cfg(any( + target_os = "android", + target_os = "illumos", + target_os = "redox", + target_os = "solaris", + target_os = "espidf", + target_os = "horizon" + ))] { + #[inline] + unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { + // On android we currently target API level 9 which unfortunately + // doesn't have the `posix_memalign` API used below. Instead we use + // `memalign`, but this unfortunately has the property on some systems + // where the memory returned cannot be deallocated by `free`! + // + // Upon closer inspection, however, this appears to work just fine with + // Android, so for this platform we should be fine to call `memalign` + // (which is present in API level 9). Some helpful references could + // possibly be chromium using memalign [1], attempts at documenting that + // memalign + free is ok [2] [3], or the current source of chromium + // which still uses memalign on android [4]. + // + // [1]: https://codereview.chromium.org/10796020/ + // [2]: https://code.google.com/p/android/issues/detail?id=35391 + // [3]: https://bugs.chromium.org/p/chromium/issues/detail?id=138579 + // [4]: https://chromium.googlesource.com/chromium/src/base/+/master/ + // /memory/aligned_memory.cc + libc::memalign(layout.align(), layout.size()) as *mut u8 + } + } else if #[cfg(target_os = "wasi")] { + #[inline] + unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { + libc::aligned_alloc(layout.align(), layout.size()) as *mut u8 + } + } else { + #[inline] + unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { + let mut out = ptr::null_mut(); + // posix_memalign requires that the alignment be a multiple of `sizeof(void*)`. + // Since these are all powers of 2, we can just use max. + let align = layout.align().max(crate::mem::size_of::<usize>()); + let ret = libc::posix_memalign(&mut out, align, layout.size()); + if ret != 0 { ptr::null_mut() } else { out as *mut u8 } + } + } +} |