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bluss opened this issue Apr 26, 2015 · 0 comments · Fixed by #24865
Closed

Overflow in Range<A> size_hint() #24851

bluss opened this issue Apr 26, 2015 · 0 comments · Fixed by #24865

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@bluss
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bluss commented Apr 26, 2015

size_hint is not implemented correctly for the ranges, it overflows:

playbot: (-1i8..127).size_hint()
-playbot:#rust-internals- (18446744073709551488, Some(18446744073709551488))

Expected result: 128

With other compilation settings, the result is:

'Error: arithmetic operation overflowed'
bluss pushed a commit to bluss/rust that referenced this issue Apr 27, 2015
core: Fix size_hint for signed integer Range<T> iterators
b519b27 
There was an overflow bug in .size_hint() for signed iterators, which
produced an hilariously incorrect size or an overflow panic.

Incorrect size is a serious bug since the iterators are marked
ExactSizeIterator. (And leads to abort() on (-1i8..127).collect() when
the collection tries to preallocate too much).

> (-1i8..127).size_hint()
(18446744073709551488, Some(18446744073709551488))

Bug found using quickcheck.

Fixes rust-lang#24851
@bluss bluss mentioned this issue Apr 27, 2015
Merged
bluss pushed a commit to bluss/rust that referenced this issue Apr 27, 2015
core: Fix size_hint for signed integer Range<T> iterators
95be21d 
There was an overflow bug in .size_hint() for signed iterators, which
produced an hilariously incorrect size or an overflow panic.

Incorrect size is a serious bug since the iterators are marked
ExactSizeIterator. (And leads to abort() on (-1i8..127).collect() when
the collection tries to preallocate too much).

All signed range iterators were affected.

> (-1i8..127).size_hint()
(18446744073709551488, Some(18446744073709551488))

Bug found using quickcheck.

Fixes rust-lang#24851
bors added a commit that referenced this issue Apr 29, 2015
@bors
Auto merge of #24865 - bluss:range-size, r=alexcrichton
c4b23ae 
core: Fix size_hint for signed integer `Range<T>` iterators

There was an overflow bug in .size_hint() for signed iterators, which
produced an hilariously incorrect size or an overflow panic.

Incorrect size is a serious bug since the iterators are marked
ExactSizeIterator. (And leads to abort() on (-1i8..127).collect() when
the collection tries to preallocate too much).

> (-1i8..127).size_hint()
(18446744073709551488, Some(18446744073709551488))

Bug found using quickcheck.

Fixes #24851
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core: Fix size_hint for signed integer Range<T> iterators bluss/rust
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@bluss