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Auto merge of #125244 - RalfJung:android-alloc, r=workingjubilee

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android: use posix_memalign for aligned allocations

Our target page says
> Rust will support the most recent Long Term Support (LTS) Android Native Development Kit (NDK). By default Rust will support all API levels supported by the NDK, but a higher minimum API level may be required if deemed necessary.

According to [this](https://github.com/android/ndk/wiki/Changelog-r26), the minimum API level of the current LTS NDK is 21. According to [this](https://stackoverflow.com/questions/44852378/android-ndk-r15b-posix-memalign-undeclared-identifier), posix_memalign exists since API level 16. So I think we should be able to use it here?
This commit is contained in:
bors 2024-05-18 15:13:33 +00:00
commit cf2baaa835
1 changed files with 1 additions and 18 deletions
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19
library/std/src/sys/pal/unix/alloc.rs
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@ -59,8 +59,8 @@ unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut
}
cfg_if::cfg_if! {
// We use posix_memalign wherever possible, but not all targets have that function.
if #[cfg(any(
target_os = "android",
target_os = "redox",
target_os = "espidf",
target_os = "horizon",
@ -68,23 +68,6 @@ unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut
))] {
#[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 {