1 use crate::alloc::{GlobalAlloc, Layout, System}; 2 use crate::ptr; 3 use crate::sys::common::alloc::{realloc_fallback, MIN_ALIGN}; 4 5 #[stable(feature = "alloc_system_type", since = "1.28.0")] 6 unsafe impl GlobalAlloc for System { 7 #[inline] alloc(&self, layout: Layout) -> *mut u88 unsafe fn alloc(&self, layout: Layout) -> *mut u8 { 9 // jemalloc provides alignment less than MIN_ALIGN for small allocations. 10 // So only rely on MIN_ALIGN if size >= align. 11 // Also see <https://github.com/rust-lang/rust/issues/45955> and 12 // <https://github.com/rust-lang/rust/issues/62251#issuecomment-507580914>. 13 if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() { 14 libc::malloc(layout.size()) as *mut u8 15 } else { 16 #[cfg(target_os = "macos")] 17 { 18 if layout.align() > (1 << 31) { 19 return ptr::null_mut(); 20 } 21 } 22 aligned_malloc(&layout) 23 } 24 } 25 26 #[inline] alloc_zeroed(&self, layout: Layout) -> *mut u827 unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 { 28 // See the comment above in `alloc` for why this check looks the way it does. 29 if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() { 30 libc::calloc(layout.size(), 1) as *mut u8 31 } else { 32 let ptr = self.alloc(layout); 33 if !ptr.is_null() { 34 ptr::write_bytes(ptr, 0, layout.size()); 35 } 36 ptr 37 } 38 } 39 40 #[inline] dealloc(&self, ptr: *mut u8, _layout: Layout)41 unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) { 42 libc::free(ptr as *mut libc::c_void) 43 } 44 45 #[inline] realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u846 unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 { 47 if layout.align() <= MIN_ALIGN && layout.align() <= new_size { 48 libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8 49 } else { 50 realloc_fallback(self, ptr, layout, new_size) 51 } 52 } 53 } 54 55 cfg_if::cfg_if! { 56 if #[cfg(any( 57 target_os = "android", 58 target_os = "illumos", 59 target_os = "redox", 60 target_os = "solaris", 61 target_os = "espidf", 62 target_os = "horizon", 63 target_os = "vita", 64 ))] { 65 #[inline] 66 unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { 67 // On android we currently target API level 9 which unfortunately 68 // doesn't have the `posix_memalign` API used below. Instead we use 69 // `memalign`, but this unfortunately has the property on some systems 70 // where the memory returned cannot be deallocated by `free`! 71 // 72 // Upon closer inspection, however, this appears to work just fine with 73 // Android, so for this platform we should be fine to call `memalign` 74 // (which is present in API level 9). Some helpful references could 75 // possibly be chromium using memalign [1], attempts at documenting that 76 // memalign + free is ok [2] [3], or the current source of chromium 77 // which still uses memalign on android [4]. 78 // 79 // [1]: https://codereview.chromium.org/10796020/ 80 // [2]: https://code.google.com/p/android/issues/detail?id=35391 81 // [3]: https://bugs.chromium.org/p/chromium/issues/detail?id=138579 82 // [4]: https://chromium.googlesource.com/chromium/src/base/+/master/ 83 // /memory/aligned_memory.cc 84 libc::memalign(layout.align(), layout.size()) as *mut u8 85 } 86 } else if #[cfg(target_os = "wasi")] { 87 #[inline] 88 unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { 89 libc::aligned_alloc(layout.align(), layout.size()) as *mut u8 90 } 91 } else { 92 #[inline] 93 unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 { 94 let mut out = ptr::null_mut(); 95 // posix_memalign requires that the alignment be a multiple of `sizeof(void*)`. 96 // Since these are all powers of 2, we can just use max. 97 let align = layout.align().max(crate::mem::size_of::<usize>()); 98 let ret = libc::posix_memalign(&mut out, align, layout.size()); 99 if ret != 0 { ptr::null_mut() } else { out as *mut u8 } 100 } 101 } 102 } 103