fix alloc_bytes (always allocate at least 1B) · rust-lang/rust@56c363b (original) (raw)
`@@ -13,10 +13,7 @@ pub struct MiriAllocBytes {
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`/// Stored layout information about the allocation.
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`layout: alloc::Layout,
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`/// Pointer to the allocation contents.
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``
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/// Invariant:
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``
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/// * If self.layout.size() == 0, then self.ptr is some suitably aligned pointer
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``
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/// without provenance (and no actual memory was allocated).
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``
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/// * Otherwise, self.ptr points to memory allocated with self.layout.
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`` +
/// Invariant: self.ptr points to memory allocated with self.layout.
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`ptr: *mut u8,
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`}
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``
`@@ -30,10 +27,8 @@ impl Clone for MiriAllocBytes {
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``
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`impl Drop for MiriAllocBytes {
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`fn drop(&mut self) {
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``
`-
if self.layout.size() != 0 {
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``
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// SAFETY: Invariant, self.ptr points to memory allocated with self.layout.
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``
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unsafe { alloc::dealloc(self.ptr, self.layout) }
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``
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}
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// SAFETY: Invariant, self.ptr points to memory allocated with self.layout.
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unsafe { alloc::dealloc(self.ptr, self.layout) }
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`}
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`}
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``
`@@ -58,25 +53,23 @@ impl std::ops::DerefMut for MiriAllocBytes {
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`impl MiriAllocBytes {
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`` /// This method factors out how a MiriAllocBytes object is allocated,
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`` /// specifically given an allocation function alloc_fn.
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``
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/// alloc_fn is only used if size != 0.
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``
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/// Returns Err(layout) if the allocation function returns a ptr that is ptr.is_null().
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/// alloc_fn is only used with size != 0.
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/// Returns Err(layout) if the allocation function returns a ptr where ptr.is_null().
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`fn alloc_with(
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`size: usize,
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`align: usize,
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`alloc_fn: impl FnOnce(Layout) -> *mut u8,
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`) -> Result<MiriAllocBytes, Layout> {
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// When size is 0 we allocate 1 byte anyway, so addresses don't possibly overlap.
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let size = if size == 0 { 1 } else { size };
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`let layout = Layout::from_size_align(size, align).unwrap();
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``
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let ptr = if size == 0 {
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``
`-
std::ptr::without_provenance_mut(align)
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let ptr = alloc_fn(layout);
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if ptr.is_null() {
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Err(layout)
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`} else {
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``
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let ptr = alloc_fn(layout);
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``
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if ptr.is_null() {
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``
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return Err(layout);
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``
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}
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``
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ptr
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``
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};
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``
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// SAFETY: All MiriAllocBytes invariants are fulfilled.
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``
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Ok(Self { ptr, layout })
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// SAFETY: All MiriAllocBytes invariants are fulfilled.
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Ok(Self { ptr, layout })
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}
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`}
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`}
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``
`@@ -85,7 +78,7 @@ impl AllocBytes for MiriAllocBytes {
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`let slice = slice.into();
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`let size = slice.len();
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`let align = align.bytes_usize();
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``
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// SAFETY: alloc_fn will only be used if size != 0.
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`` +
// SAFETY: alloc_fn will only be used with size != 0.
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`let alloc_fn = |layout| unsafe { alloc::alloc(layout) };
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`let alloc_bytes = MiriAllocBytes::alloc_with(size, align, alloc_fn)
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`.unwrap_or_else(|layout| alloc::handle_alloc_error(layout));
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`@@ -98,7 +91,7 @@ impl AllocBytes for MiriAllocBytes {
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`fn zeroed(size: Size, align: Align) -> Option {
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`let size = size.bytes_usize();
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`let align = align.bytes_usize();
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``
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// SAFETY: alloc_fn will only be used if size != 0.
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`` +
// SAFETY: alloc_fn will only be used with size != 0.
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`let alloc_fn = |layout| unsafe { alloc::alloc_zeroed(layout) };
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`MiriAllocBytes::alloc_with(size, align, alloc_fn).ok()
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`}
`