| 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 { |
| // `posix_memalign` returns a non-aligned value if supplied a very |
| // large alignment on older versions of Apple's platforms (unknown |
| // exactly which version range, but the issue is definitely |
| // present in macOS 10.14 and iOS 13.3). |
| // |
| // <https://github.com/rust-lang/rust/issues/30170> |
| #[cfg(target_vendor = "apple")] |
| { |
| 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! { |
| // We use posix_memalign wherever possible, but not all targets have that function. |
| if #[cfg(any( |
| target_os = "redox", |
| target_os = "espidf", |
| target_os = "horizon", |
| target_os = "vita", |
| ))] { |
| #[inline] |
| unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { |
| libc::memalign(layout.align(), layout.size()) as *mut u8 |
| } |
| } else { |
| #[inline] |
| unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { |
| let mut out = ptr::null_mut(); |
| // We prefer posix_memalign over aligned_malloc since with aligned_malloc, |
| // implementations are making almost arbitrary choices for which alignments are |
| // "supported", making it hard to use. For instance, some implementations require the |
| // size to be a multiple of the alignment (wasi emmalloc), while others require the |
| // alignment to be at least the pointer size (Illumos, macOS) -- which may or may not be |
| // standards-compliant, but that does not help us. |
| // posix_memalign only has one, clear requirement: 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 } |
| } |
| } |
| } |