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Fix over-alignment assert crash on Android.

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This commit is contained in:
Imanol Fernandez 2017-06-17 00:36:47 +02:00
parent 81275234aa
commit 58e887658d
1 changed files with 18 additions and 6 deletions
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24
components/servo_arc/lib.rs
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@ -527,12 +527,16 @@ impl<H, T> Arc<HeaderSlice<H, [T]>> {
//
// To avoid alignment issues, we allocate words rather than bytes,
// rounding up to the nearest word size.
assert!(mem::align_of::<T>() <= mem::align_of::<usize>(),
"We don't handle over-aligned types");
let words_to_allocate = divide_rounding_up(size, size_of::<usize>());
let mut vec = Vec::<usize>::with_capacity(words_to_allocate);
vec.set_len(words_to_allocate);
let buffer = Box::into_raw(vec.into_boxed_slice()) as *mut usize as *mut u8;
let buffer = if mem::align_of::<T>() <= mem::align_of::<usize>() {
Self::allocate_buffer::<usize>(size)
} else if mem::align_of::<T>() <= mem::align_of::<u64>() {
// On 32-bit platforms <T> may have 8 byte alignment while usize has 4 byte aligment.
// Use u64 to avoid over-alignment.
// This branch will compile away in optimized builds.
Self::allocate_buffer::<u64>(size)
} else {
panic!("Over-aligned type not handled");
};
// Synthesize the fat pointer. We do this by claiming we have a direct
// pointer to a [T], and then changing the type of the borrow. The key
@ -564,6 +568,14 @@ impl<H, T> Arc<HeaderSlice<H, [T]>> {
assert_eq!(size_of::<Self>(), size_of::<usize>() * 2, "The Arc will be fat");
Arc { p: NonZeroPtrMut::new(ptr) }
}
#[inline]
unsafe fn allocate_buffer<W>(size: usize) -> *mut u8 {
let words_to_allocate = divide_rounding_up(size, mem::size_of::<W>());
let mut vec = Vec::<W>::with_capacity(words_to_allocate);
vec.set_len(words_to_allocate);
Box::into_raw(vec.into_boxed_slice()) as *mut W as *mut u8
}
}
/// Header data with an inline length. Consumers that use HeaderWithLength as the