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Add fuzzy pointer comparison intrinsics

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This commit is contained in:
Oliver Scherer 2020-06-16 10:37:34 +02:00
parent 9245ba8304
commit e09b620339
14 changed files with 260 additions and 22 deletions
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5
src/test/ui/error-codes/E0395.stderr
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@ -4,8 +4,9 @@ error: pointers cannot be compared in a meaningful way during const eval.
LL | static BAZ: bool = unsafe { (&FOO as *const i32) == (&BAR as *const i32) };
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: It is conceptually impossible for const eval to know in all cases whether two pointers are equal. While sometimes it is clear (the address of a static item is never equal to the address of another static item), comparing an integer address with any allocation's address is impossible to do at compile-time.
= note: That said, there's the `ptr_maybe_eq` intrinsic which returns `true` for all comparisons where CTFE isn't sure whether two addresses are equal. The mirror intrinsic `ptr_maybe_ne` returns `true` for all comparisons where CTFE isn't sure whether two addresses are inequal.
= note: see issue #53020 <https://github.com/rust-lang/rust/issues/53020> for more information
= note: It is conceptually impossible for const eval to know in all cases whether two pointers are equal. While sometimes it is clear (the address of a non-zst static item is never equal to the address of another non-zst static item), comparing an integer address with any allocation's address is impossible to do at compile-time.
= note: That said, there's the `<*const T>::guaranteed_eq` intrinsic which returns `true` for all comparisons where CTFE is sure that two addresses are equal. The mirror intrinsic `<*const T>::guaranteed_ne` returns `true` for all comparisons where CTFE is sure that two addresses are inequal.
error: aborting due to previous error