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add an attribute for omitting the drop flag #7138

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thestinger opened this issue Jun 15, 2013 · 1 comment
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add an attribute for omitting the drop flag #7138

thestinger opened this issue Jun 15, 2013 · 1 comment
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I-slow Issue: Problems and improvements with respect to performance of generated code.

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@thestinger
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For smart pointers to be implemented as library types, the drop flag needs to be omitted and the pointer zeroed instead. Calling the destructor more than once will be fine, free is a no-op on null pointers.
@thestinger thestinger mentioned this issue Jun 21, 2013
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@Aatch Aatch mentioned this issue Jun 23, 2013
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bors added a commit that referenced this issue Jun 25, 2013
@bors
auto merge of #7317 : Aatch/rust/no-drop-flag, r=thestinger
d161e63 
This adds a `#[no_drop_flag]` attribute. This attribute tells the compiler to omit the drop flag from the struct, if it has a destructor. When the destructor is run, instead of setting the drop flag, it instead zeroes-out the struct. This means the destructor can run multiple times and therefore it is up to the developer to use it safely.

The primary usage case for this is smart-pointer types like `Rc<T>` as the extra flag caused the struct to be 1 word larger because of alignment.

This closes #7271 and #7138
@thestinger
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Fixed.

flip1995 pushed a commit to flip1995/rust that referenced this issue Apr 27, 2021
@bors
Auto merge of rust-lang#7138 - mgacek8:issue6808_iter_cloned_collect_…
9af07e6 
…FN_with_large_array, r=Manishearth

Fix FN in `iter_cloned_collect` with a large array

fixes rust-lang#6808
changelog: Fix FN in `iter_cloned_collect` with a large array

I spotted that [is_iterable_array](https://github.com/rust-lang/rust-clippy/blob/a362a4d1d0edb66aef186c1d27b28c60573078f4/clippy_lints/src/loops/explicit_iter_loop.rs#L67-L75) function that `explicit_iter_loop` lint is using only works for array sizes <= 32.
There is this comment:
> IntoIterator is currently only implemented for array sizes <= 32 in rustc

I'm a bit confused, because I read that [IntoIterator for arrays](https://doc.rust-lang.org/src/core/array/mod.rs.html#194-201) with const generic `N` is stable since = "1.0.0". Although Const Generics MVP were stabilized in Rust 1.51.

Should I set MSRV for the current change? I will try to test with older compilers soon.
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@thestinger