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Correctly document is_null CTFE behavior. #134325

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Correctly document is_null CTFE behavior. #134325

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16 changes: 10 additions & 6 deletions library/core/src/ptr/const_ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,12 +14,16 @@ impl<T: ?Sized> *const T {
///
/// ## Behavior during const evaluation
///
/// When this function is used during const evaluation, it may return `false` for pointers
/// that turn out to be null at runtime. Specifically, when a pointer to some memory
/// is offset beyond its bounds in such a way that the resulting pointer is null,
/// the function will still return `false`. There is no way for CTFE to know
/// the absolute position of that memory, so we cannot tell if the pointer is
/// null or not.
/// When this function is used during const evaluation, this function will
/// panic if CTFE cannot determine whether the pointer is null or not. This
/// panic might or might not occur when `self` is a pointer that is offset
/// beyond the bounds of the memory it initially pointed to. Conversely,
/// this panic will never occur when `self` is in-bounds.
///
/// This inability to determine nullness occurs because there is no way for
/// CTFE to know the absolute position of that memory, so it might or might
/// not be possible to determine whether an offset out of bounds happens to
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Suggested change
/// not be possible to determine whether an offset out of bounds happens to
/// not be possible to determine whether an out-of-bounds offset happens to

/// result in a null pointer.
///
/// # Examples
///
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16 changes: 10 additions & 6 deletions library/core/src/ptr/mut_ptr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,12 +14,16 @@ impl<T: ?Sized> *mut T {
///
/// ## Behavior during const evaluation
///
/// When this function is used during const evaluation, it may return `false` for pointers
/// that turn out to be null at runtime. Specifically, when a pointer to some memory
/// is offset beyond its bounds in such a way that the resulting pointer is null,
/// the function will still return `false`. There is no way for CTFE to know
/// the absolute position of that memory, so we cannot tell if the pointer is
/// null or not.
/// When this function is used during const evaluation, this function will
/// panic if CTFE cannot determine whether the pointer is null or not. This
/// panic might or might not occur when `self` is a pointer that is offset
/// beyond the bounds of the memory it initially pointed to. Conversely,
/// this panic will never occur when `self` is in-bounds.
///
/// This inability to determine nullness occurs because there is no way for
/// CTFE to know the absolute position of that memory, so it might or might
/// not be possible to determine whether an offset out of bounds happens to
/// result in a null pointer.
///
/// # Examples
///
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