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use crate::ptr;
use crate::sys_common::alloc::{MIN_ALIGN, realloc_fallback};
use crate::alloc::{GlobalAlloc, Layout, System};
#[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(any(target_os = "android",
target_os = "hermit",
target_os = "redox",
target_os = "solaris"))]
#[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
}
#[cfg(not(any(target_os = "android",
target_os = "hermit",
target_os = "redox",
target_os = "solaris")))]
#[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
}
}
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