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use super::{realloc_fallback, MIN_ALIGN};
use crate::alloc::{GlobalAlloc, Layout, System};
use crate::ptr;
#[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() {
unsafe { 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();
}
}
unsafe { 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() {
unsafe { libc::calloc(layout.size(), 1) as *mut u8 }
} else {
let ptr = unsafe { self.alloc(layout) };
if !ptr.is_null() {
unsafe { ptr::write_bytes(ptr, 0, layout.size()) };
}
ptr
}
}
#[inline]
unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
unsafe { 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 {
unsafe { libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8 }
} else {
unsafe { realloc_fallback(self, ptr, layout, new_size) }
}
}
}
cfg_if::cfg_if! {
// We use posix_memalign wherever possible, but some targets have very incomplete POSIX coverage
// so we need a fallback for those.
if #[cfg(any(
target_os = "horizon",
target_os = "vita",
))] {
#[inline]
unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
unsafe { 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_alloc since it is more widely available, and
// since with aligned_alloc, 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).
// 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 = unsafe { libc::posix_memalign(&mut out, align, layout.size()) };
if ret != 0 { ptr::null_mut() } else { out as *mut u8 }
}
}
}