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Merged
merged 5 commits into from
Aug 26, 2014
Merged

DST coercions and DST fields in structs #14397

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34d607f
Use the slice repr for ~[T]
nrc Apr 25, 2014
37a94b8
Use temp vars for implicit coercion to ^[T]
nrc Aug 4, 2014
3e62637
DST coercions and DST structs
nrc Aug 4, 2014
52ef462
Rebasing changes
nrc Aug 6, 2014
08364a4
Optimise a particularly clown shoes example of DST codegen
nrc Aug 26, 2014
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6 changes: 6 additions & 0 deletions src/liballoc/heap.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
// FIXME: #13996: mark the `allocate` and `reallocate` return value as `noalias`
// and `nonnull`

use core::ptr::RawPtr;
#[cfg(not(test))] use core::raw;
#[cfg(not(test))] use util;

Expand Down Expand Up @@ -69,6 +70,11 @@ pub unsafe fn reallocate_inplace(ptr: *mut u8, size: uint, align: uint,
/// the value returned by `usable_size` for the requested size.
#[inline]
pub unsafe fn deallocate(ptr: *mut u8, size: uint, align: uint) {
// FIXME(14395) This is only required for DST ~[T], it should be removed once
// we fix that representation to not use null pointers.
if ptr.is_null() {
return;
}
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The drop glue has the responsibility to not do anything if the entire value is zeroed - structures with a Drop impl have a drop flag by default, and pointers use null values.
For ~T/Box<T>, drop glue makes the null check. I would've expected ~[T]/Box<[T]> to be even more like that after this change.

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Drop glue should make the null check, but it was not trivial to do (probably easy, but not trivial - I got bugs which I didn't start to investigate), so I left it for a follow up (the 'hard' case is when the vec has length 0, then I use a null pointer inside the fat pointer).

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nit: put an octothorpe (#) in front of the number in the fixme.

imp::deallocate(ptr, size, align)
}

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2 changes: 1 addition & 1 deletion src/libcollections/bitv.rs
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Expand Up @@ -2557,7 +2557,7 @@ mod tests {
}

fn rng() -> rand::IsaacRng {
let seed = &[1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
let seed: &[_] = &[1, 2, 3, 4, 5, 6, 7, 8, 9, 0];
rand::SeedableRng::from_seed(seed)
}

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3 changes: 2 additions & 1 deletion src/libcollections/dlist.rs
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Expand Up @@ -1088,7 +1088,8 @@ mod tests {
let n = list_from([1i,2,3]);
spawn(proc() {
check_links(&n);
assert_eq!(&[&1,&2,&3], n.iter().collect::<Vec<&int>>().as_slice());
let a: &[_] = &[&1,&2,&3];
assert_eq!(a, n.iter().collect::<Vec<&int>>().as_slice());
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here and elsewhere: Does the <expr> as <type> syntax work yet for coercing a sized type to an unsized one?

E.g. could we here instead write assert_eq!(&[&1,&2,&3] as &[_], n.iter().collect::<Vec<&int>>().as_slice()); ?

I am not sure if it would actually make things look nicer, but it might help stress that a coercion is happening here, not just a type assertion.

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It does not. From what I could tell at the time, the as syntax was for casts and coercions were always implicit. In retrospect, I think I am wrong about that. I envisaged addressing this with type ascription. But I think that highlights some potentially confusing overlap between type ascription and explicit casts.

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(I might be using the term "coercion" incorrectly here. anyway the point is whether we have any expression form, other than a let nested in an ExprBlock, for turning a thin pointer into a fat one. But it sounds like we do not have that yet.)

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@nick29581 Anyway, if possible, when you squash your commits together, I would appreciate it if you put these preparatory refactorings on a separate early commit, so that people looking at the history can easily focus in on the substansive changes.

});
}

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3 changes: 2 additions & 1 deletion src/libcollections/hash/mod.rs
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Expand Up @@ -346,7 +346,8 @@ mod tests {
assert_eq!(hasher.hash(&'a'), 97);

assert_eq!(hasher.hash(&("a")), 97 + 0xFF);
assert_eq!(hasher.hash(& &[1u8, 2u8, 3u8]), 9);
let cs: &[u8] = &[1u8, 2u8, 3u8];
assert_eq!(hasher.hash(& cs), 9);

unsafe {
let ptr: *const int = mem::transmute(5i);
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4 changes: 2 additions & 2 deletions src/libcollections/hash/sip.rs
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Expand Up @@ -495,8 +495,8 @@ mod tests {
assert!(s != t && t != u);
assert!(hash(&s) != hash(&t) && hash(&s) != hash(&u));

let v = (&[1u8], &[0u8, 0], &[0u8]);
let w = (&[1u8, 0, 0, 0], &[], &[]);
let v: (&[u8], &[u8], &[u8]) = (&[1u8], &[0u8, 0], &[0u8]);
let w: (&[u8], &[u8], &[u8]) = (&[1u8, 0, 0, 0], &[], &[]);

assert!(v != w);
assert!(hash(&v) != hash(&w));
Expand Down
24 changes: 18 additions & 6 deletions src/libcollections/ringbuf.rs
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Expand Up @@ -243,7 +243,8 @@ impl<T> RingBuf<T> {
/// buf.push(5i);
/// buf.push(3);
/// buf.push(4);
/// assert_eq!(buf.iter().collect::<Vec<&int>>().as_slice(), &[&5, &3, &4]);
/// let b: &[_] = &[&5, &3, &4];
/// assert_eq!(buf.iter().collect::<Vec<&int>>().as_slice(), b);
/// ```
pub fn iter<'a>(&'a self) -> Items<'a, T> {
Items{index: 0, rindex: self.nelts, lo: self.lo, elts: self.elts.as_slice()}
Expand All @@ -263,7 +264,8 @@ impl<T> RingBuf<T> {
/// for num in buf.mut_iter() {
/// *num = *num - 2;
/// }
/// assert_eq!(buf.mut_iter().collect::<Vec<&mut int>>().as_slice(), &[&mut 3, &mut 1, &mut 2]);
/// let b: &[_] = &[&mut 3, &mut 1, &mut 2];
/// assert_eq!(buf.mut_iter().collect::<Vec<&mut int>>().as_slice(), b);
/// ```
pub fn mut_iter<'a>(&'a mut self) -> MutItems<'a, T> {
let start_index = raw_index(self.lo, self.elts.len(), 0);
Expand Down Expand Up @@ -865,12 +867,18 @@ mod tests {
for i in range(0i, 5) {
d.push_back(i);
}
assert_eq!(d.iter().collect::<Vec<&int>>().as_slice(), &[&0,&1,&2,&3,&4]);
{
let b: &[_] = &[&0,&1,&2,&3,&4];
assert_eq!(d.iter().collect::<Vec<&int>>().as_slice(), b);
}

for i in range(6i, 9) {
d.push_front(i);
}
assert_eq!(d.iter().collect::<Vec<&int>>().as_slice(), &[&8,&7,&6,&0,&1,&2,&3,&4]);
{
let b: &[_] = &[&8,&7,&6,&0,&1,&2,&3,&4];
assert_eq!(d.iter().collect::<Vec<&int>>().as_slice(), b);
}

let mut it = d.iter();
let mut len = d.len();
Expand All @@ -890,12 +898,16 @@ mod tests {
for i in range(0i, 5) {
d.push_back(i);
}
assert_eq!(d.iter().rev().collect::<Vec<&int>>().as_slice(), &[&4,&3,&2,&1,&0]);
{
let b: &[_] = &[&4,&3,&2,&1,&0];
assert_eq!(d.iter().rev().collect::<Vec<&int>>().as_slice(), b);
}

for i in range(6i, 9) {
d.push_front(i);
}
assert_eq!(d.iter().rev().collect::<Vec<&int>>().as_slice(), &[&4,&3,&2,&1,&0,&6,&7,&8]);
let b: &[_] = &[&4,&3,&2,&1,&0,&6,&7,&8];
assert_eq!(d.iter().rev().collect::<Vec<&int>>().as_slice(), b);
}

#[test]
Expand Down
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