rust/compiler/rustc_const_eval
bors 591ecb88df Auto merge of #128742 - RalfJung:miri-vtable-uniqueness, r=saethlin
miri: make vtable addresses not globally unique

Miri currently gives vtables a unique global address. That's not actually matching reality though. So this PR enables Miri to generate different addresses for the same type-trait pair.

To avoid generating an unbounded number of `AllocId` (and consuming unbounded amounts of memory), we use the "salt" technique that we also already use for giving constants non-unique addresses: the cache is keyed on a "salt" value n top of the actually relevant key, and Miri picks a random salt (currently in the range `0..16`) each time it needs to choose an `AllocId` for one of these globals -- that means we'll get up to 16 different addresses for each vtable. The salt scheme is integrated into the global allocation deduplication logic in `tcx`, and also used for functions and string literals. (So this also fixes the problem that casting the same function to a fn ptr over and over will consume unbounded memory.)

r? `@saethlin`
Fixes https://github.com/rust-lang/miri/issues/3737
2024-08-13 04:32:34 +00:00
..
src Auto merge of #128742 - RalfJung:miri-vtable-uniqueness, r=saethlin 2024-08-13 04:32:34 +00:00
Cargo.toml Clean up rustc_*/Cargo.toml. 2023-10-30 08:46:02 +11:00
messages.ftl rustc_const_eval: make LazyLock suggestion translatable 2024-08-10 14:32:55 +03:00