Use box syntax instead of Box::new in Mutex::remutex on Windows#49646
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bors merged 1 commit intorust-lang:masterfrom Apr 16, 2018
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Use box syntax instead of Box::new in Mutex::remutex on Windows#49646bors merged 1 commit intorust-lang:masterfrom
bors merged 1 commit intorust-lang:masterfrom
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The Box::new(mem::uninitialized()) pattern actually actively copies uninitialized bytes from the stack into the box, which is a waste of time. Using the box syntax instead avoids the useless copy.
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It surprises me that this would make a difference, given that Just thinking aloud, I wonder if there's a way to fix |
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Ping from triage! This PR needs a review. Can @withoutboats or someone else from @rust-lang/libs review this? |
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@bors: r+ rollup |
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📌 Commit 4577da7 has been approved by |
kennytm
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Apr 16, 2018
…richton Use box syntax instead of Box::new in Mutex::remutex on Windows The Box::new(mem::uninitialized()) pattern actually actively copies uninitialized bytes from the stack into the box, which is a waste of time. Using the box syntax instead avoids the useless copy.
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Apr 16, 2018
Rollup of 8 pull requests Successful merges: - #49555 (Inline most of the code paths for conversions with boxed slices) - #49606 (Prevent broken pipes causing ICEs) - #49646 (Use box syntax instead of Box::new in Mutex::remutex on Windows) - #49647 (Remove `underscore_lifetimes` and `match_default_bindings` from active feature list) - #49931 (Fix incorrect span in `&mut` suggestion) - #49959 (rustbuild: allow building tools with debuginfo) - #49965 (Remove warning about f64->f32 cast being potential UB) - #49994 (Remove unnecessary indentation in rustdoc book codeblock.) Failed merges:
bors
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Aug 18, 2021
Remove box syntax from compiler and tools Removes box syntax from the compiler and tools. In rust-lang#49733, the future of box syntax is uncertain and the use in the compiler was listed as one of the reasons to keep it. Removal of box syntax [might affect the code generated](rust-lang#49646 (comment)) and slow down the compiler so I'd recommend doing a perf run on this.
christian-schilling
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Jan 27, 2026
Remove box syntax from compiler and tools Removes box syntax from the compiler and tools. In #49733, the future of box syntax is uncertain and the use in the compiler was listed as one of the reasons to keep it. Removal of box syntax [might affect the code generated](rust-lang/rust#49646 (comment)) and slow down the compiler so I'd recommend doing a perf run on this.
christian-schilling
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Jan 27, 2026
Remove box syntax from compiler and tools Removes box syntax from the compiler and tools. In #49733, the future of box syntax is uncertain and the use in the compiler was listed as one of the reasons to keep it. Removal of box syntax [might affect the code generated](rust-lang/rust#49646 (comment)) and slow down the compiler so I'd recommend doing a perf run on this.
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The Box::new(mem::uninitialized()) pattern actually actively copies
uninitialized bytes from the stack into the box, which is a waste of
time. Using the box syntax instead avoids the useless copy.