mentions provenance, changes argument type, adds must_use attr
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@ -662,6 +662,11 @@ impl<T: ?Sized> *const T {
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/// will only affect the pointer part, whereas for (thin) pointers to
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/// sized types, this has the same effect as a simple assignment.
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///
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/// The resulting pointer will have provenance of `val`, i.e., for a fat
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/// pointer, this operation is semantically the same as creating a new
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/// fat pointer with the data pointer value of `val` but the metadata of
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/// `self`.
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///
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/// # Examples
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///
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/// This function is primarily useful for allowing byte-wise pointer
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@ -673,13 +678,17 @@ impl<T: ?Sized> *const T {
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/// let arr: [i32; 3] = [1, 2, 3];
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/// let mut ptr = &arr[0] as *const dyn Debug;
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/// let thin = ptr as *const u8;
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/// ptr = ptr.set_ptr_value(unsafe { thin.add(8).cast() });
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/// assert_eq!(unsafe { *(ptr as *const i32) }, 3);
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/// unsafe {
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/// ptr = ptr.set_ptr_value(thin.add(8));
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/// # assert_eq!(*(ptr as *const i32), 3);
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/// println!("{:?}", &*ptr); // will print "3"
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/// }
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/// ```
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#[unstable(feature = "set_ptr_value", issue = "75091")]
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#[must_use = "returns a new pointer rather than modifying its argument"]
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#[inline]
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pub fn set_ptr_value(mut self, val: *const ()) -> Self {
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let thin = &mut self as *mut *const T as *mut *const ();
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pub fn set_ptr_value(mut self, val: *const u8) -> Self {
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let thin = &mut self as *mut *const T as *mut *const u8;
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// SAFETY: In case of a thin pointer, this operations is identical
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// to a simple assignment. In case of a fat pointer, with the current
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// fat pointer layout implementation, the first field of such a
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@ -718,6 +718,11 @@ impl<T: ?Sized> *mut T {
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/// will only affect the pointer part, whereas for (thin) pointers to
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/// sized types, this has the same effect as a simple assignment.
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///
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/// The resulting pointer will have provenance of `val`, i.e., for a fat
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/// pointer, this operation is semantically the same as creating a new
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/// fat pointer with the data pointer value of `val` but the metadata of
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/// `self`.
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///
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/// # Examples
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///
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/// This function is primarily useful for allowing byte-wise pointer
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@ -729,13 +734,17 @@ impl<T: ?Sized> *mut T {
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/// let mut arr: [i32; 3] = [1, 2, 3];
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/// let mut ptr = &mut arr[0] as *mut dyn Debug;
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/// let thin = ptr as *mut u8;
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/// ptr = ptr.set_ptr_value(unsafe { thin.add(8).cast() });
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/// assert_eq!(unsafe { *(ptr as *mut i32) }, 3);
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/// unsafe {
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/// ptr = ptr.set_ptr_value(thin.add(8));
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/// # assert_eq!(*(ptr as *mut i32), 3);
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/// println!("{:?}", &*ptr); // will print "3"
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/// }
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/// ```
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#[unstable(feature = "set_ptr_value", issue = "75091")]
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#[must_use = "returns a new pointer rather than modifying its argument"]
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#[inline]
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pub fn set_ptr_value(mut self, val: *mut ()) -> Self {
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let thin = &mut self as *mut *mut T as *mut *mut ();
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pub fn set_ptr_value(mut self, val: *mut u8) -> Self {
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let thin = &mut self as *mut *mut T as *mut *mut u8;
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// SAFETY: In case of a thin pointer, this operations is identical
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// to a simple assignment. In case of a fat pointer, with the current
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// fat pointer layout implementation, the first field of such a
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