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Auto merge of #39304 - jrmuizel:drop-flags, r=steveklabnik 

Remove obsolete documentation about drop-flags
This commit is contained in:
bors 2017-02-20 05:51:11 +00:00
parent 322f0d7055 4ba6e1b688
commit e06774ece3
1 changed files with 2 additions and 14 deletions
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16
src/doc/nomicon/src/drop-flags.md
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@ -79,17 +79,5 @@ if condition {
}
```
As of Rust 1.0, the drop flags are actually not-so-secretly stashed in a hidden
field of any type that implements Drop. Rust sets the drop flag by overwriting
the entire value with a particular bit pattern. This is pretty obviously Not
The Fastest and causes a bunch of trouble with optimizing code. It's legacy from
a time when you could do much more complex conditional initialization.
As such work is currently under way to move the flags out onto the stack frame
where they more reasonably belong. Unfortunately, this work will take some time
as it requires fairly substantial changes to the compiler.
Regardless, Rust programs don't need to worry about uninitialized values on
the stack for correctness. Although they might care for performance. Thankfully,
Rust makes it easy to take control here! Uninitialized values are there, and
you can work with them in Safe Rust, but you're never in danger.
The drop flags are tracked on the stack and no longer stashed in types that
implement drop.