Remove null check from heap::deallocate #14395
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I-slow
Issue: Problems and improvements with respect to performance of generated code.
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FWIW, |
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@nick29581: It seems that @luqmana landed the non-null pointer optimization for slices so this shouldn't be required anymore. Can it be closed? |
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This ended up landing as part of the initial implementation, but I don't think it is actually accomplishing anything. |
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Sep 11, 2014
The pointer in the slice must not be null, because enum representations make that assumption. The `exchange_malloc` function returns a non-null sentinel for the zero size case, and it must not be passed to the `exchange_free` lang item. Since the length is always equal to the true capacity, a branch on the length is enough for most types. Slices of zero size types are statically special cased to never attempt deallocation. This is the same implementation as `Vec<T>`. Closes #14395
flip1995
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Apr 3, 2025
Closes rust-lang#10074 changelog: [`redundant_clone`]: fix FP on enum cast
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I added this to get DST landed. For
~[T]types I use a{ptr, len}fat pointer. If the vector is empy I use null for the pointer, so when this deallocates via drop glue jemalloc segfaults. It should be fairly easy to do a zero sized allocation or something and use that value and then we can remove the null check. That also allows us to use the Option to non-null pointer optimisation. For now I just want to get this branch landed though.cc @thestinger, @alexcrichton
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