2013-04-10 13:47:53 +00:00
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// This assumes the packed and non-packed structs are different sizes.
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// the error points to the start of the file, not the line with the
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// transmute
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2018-12-21 14:15:47 +00:00
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// error-pattern: cannot transmute between types of different sizes, or dependently-sized types
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2013-04-10 13:47:53 +00:00
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core: Remove the cast module
This commit revisits the `cast` module in libcore and libstd, and scrutinizes
all functions inside of it. The result was to remove the `cast` module entirely,
folding all functionality into the `mem` module. Specifically, this is the fate
of each function in the `cast` module.
* transmute - This function was moved to `mem`, but it is now marked as
#[unstable]. This is due to planned changes to the `transmute`
function and how it can be invoked (see the #[unstable] comment).
For more information, see RFC 5 and #12898
* transmute_copy - This function was moved to `mem`, with clarification that is
is not an error to invoke it with T/U that are different
sizes, but rather that it is strongly discouraged. This
function is now #[stable]
* forget - This function was moved to `mem` and marked #[stable]
* bump_box_refcount - This function was removed due to the deprecation of
managed boxes as well as its questionable utility.
* transmute_mut - This function was previously deprecated, and removed as part
of this commit.
* transmute_mut_unsafe - This function doesn't serve much of a purpose when it
can be achieved with an `as` in safe code, so it was
removed.
* transmute_lifetime - This function was removed because it is likely a strong
indication that code is incorrect in the first place.
* transmute_mut_lifetime - This function was removed for the same reasons as
`transmute_lifetime`
* copy_lifetime - This function was moved to `mem`, but it is marked
`#[unstable]` now due to the likelihood of being removed in
the future if it is found to not be very useful.
* copy_mut_lifetime - This function was also moved to `mem`, but had the same
treatment as `copy_lifetime`.
* copy_lifetime_vec - This function was removed because it is not used today,
and its existence is not necessary with DST
(copy_lifetime will suffice).
In summary, the cast module was stripped down to these functions, and then the
functions were moved to the `mem` module.
transmute - #[unstable]
transmute_copy - #[stable]
forget - #[stable]
copy_lifetime - #[unstable]
copy_mut_lifetime - #[unstable]
[breaking-change]
2014-05-09 17:34:51 +00:00
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use std::mem;
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2013-05-25 02:35:29 +00:00
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2014-05-27 06:56:52 +00:00
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#[repr(packed)]
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2013-04-10 13:47:53 +00:00
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struct Foo<T,S> {
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bar: T,
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baz: S
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}
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struct Oof<T, S> {
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rab: T,
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zab: S
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}
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fn main() {
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let foo = Foo { bar: [1u8, 2, 3, 4, 5], baz: 10i32 };
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unsafe {
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2014-12-20 02:20:51 +00:00
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let oof: Oof<[u8; 5], i32> = mem::transmute(foo);
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2015-02-05 16:58:30 +00:00
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println!("{:?} {:?}", &oof.rab[..], oof.zab);
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2013-04-10 13:47:53 +00:00
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}
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}
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