fix handling of base address for TypeId allocations #144187
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RalfJung
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Jul 19, 2025
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Nothing really changes here, but I looked at the code to ensure it is correct for TypeId and realized some ways in which it, and the comments, could be improved.
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Is it intentional that this PR does not fix the |
Yes, catching UB is not a requirement for CTFE as it has significant impact on compile times. A program that does UB if two type ids do not match may suddenly stop erroring with the next compiler release, or error even if the type ids match. |
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Also, you can't use it to get a |
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#144169 landed so this PR is no longer blocked. |
oli-obk
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Jul 21, 2025
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@bors r+ rollup |
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fix handling of base address for TypeId allocations This fixes the problems discovered by `@theemathas` in rust-lang#142789: - const-eval would sometimes consider TypeId pointers to be null - the type ID is different in Miri than in regular executions Both boil down to the same issue: the TypeId "allocation" has a guaranteed 0 base address, but const-eval assumes it was non-zero (like normal allocations) and Miri randomized it (like normal allocations). r? `@oli-obk`
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fix handling of base address for TypeId allocations This fixes the problems discovered by ``@theemathas`` in rust-lang#142789: - const-eval would sometimes consider TypeId pointers to be null - the type ID is different in Miri than in regular executions Both boil down to the same issue: the TypeId "allocation" has a guaranteed 0 base address, but const-eval assumes it was non-zero (like normal allocations) and Miri randomized it (like normal allocations). r? ``@oli-obk``
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fix handling of base address for TypeId allocations This fixes the problems discovered by ```@theemathas``` in rust-lang#142789: - const-eval would sometimes consider TypeId pointers to be null - the type ID is different in Miri than in regular executions Both boil down to the same issue: the TypeId "allocation" has a guaranteed 0 base address, but const-eval assumes it was non-zero (like normal allocations) and Miri randomized it (like normal allocations). r? ```@oli-obk```
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Rollup of 15 pull requests Successful merges: - #142097 (gpu offload host code generation) - #143430 (Lower extra lifetimes before normal generic params.) - #143672 (Fix Box allocator drop elaboration) - #143768 (Constify Try, From, TryFrom and relevant traits) - #143816 (Implement `check` for compiletest and RA using tool macro) - #143985 (rustc_public: de-StableMIR-ize) - #144027 (clippy: make tests work in stage 1) - #144080 (Mitigate `#[align]` name resolution ambiguity regression with a rename) - #144176 (Add approval blocking labels for new bors) - #144187 (fix handling of base address for TypeId allocations) - #144212 (Remove the ptr_unique lang item) - #144243 (Subtree update of `rust-analyzer`) - #144246 (Don't use another main test file as auxiliary) - #144251 (rustc-dev-guide subtree update) - #144254 (opt-dist: make `artifact-dir` an absolute path for `opt-dist local`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup of 14 pull requests Successful merges: - #142097 (gpu offload host code generation) - #143430 (Lower extra lifetimes before normal generic params.) - #143768 (Constify Try, From, TryFrom and relevant traits) - #143816 (Implement `check` for compiletest and RA using tool macro) - #143985 (rustc_public: de-StableMIR-ize) - #144027 (clippy: make tests work in stage 1) - #144080 (Mitigate `#[align]` name resolution ambiguity regression with a rename) - #144176 (Add approval blocking labels for new bors) - #144187 (fix handling of base address for TypeId allocations) - #144212 (Remove the ptr_unique lang item) - #144243 (Subtree update of `rust-analyzer`) - #144246 (Don't use another main test file as auxiliary) - #144251 (rustc-dev-guide subtree update) - #144254 (opt-dist: make `artifact-dir` an absolute path for `opt-dist local`) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of #144187 - RalfJung:type-id-base-addr, r=oli-obk fix handling of base address for TypeId allocations This fixes the problems discovered by ````@theemathas```` in #142789: - const-eval would sometimes consider TypeId pointers to be null - the type ID is different in Miri than in regular executions Both boil down to the same issue: the TypeId "allocation" has a guaranteed 0 base address, but const-eval assumes it was non-zero (like normal allocations) and Miri randomized it (like normal allocations). r? ````@oli-obk````
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Rollup of 14 pull requests Successful merges: - rust-lang/rust#142097 (gpu offload host code generation) - rust-lang/rust#143430 (Lower extra lifetimes before normal generic params.) - rust-lang/rust#143768 (Constify Try, From, TryFrom and relevant traits) - rust-lang/rust#143816 (Implement `check` for compiletest and RA using tool macro) - rust-lang/rust#143985 (rustc_public: de-StableMIR-ize) - rust-lang/rust#144027 (clippy: make tests work in stage 1) - rust-lang/rust#144080 (Mitigate `#[align]` name resolution ambiguity regression with a rename) - rust-lang/rust#144176 (Add approval blocking labels for new bors) - rust-lang/rust#144187 (fix handling of base address for TypeId allocations) - rust-lang/rust#144212 (Remove the ptr_unique lang item) - rust-lang/rust#144243 (Subtree update of `rust-analyzer`) - rust-lang/rust#144246 (Don't use another main test file as auxiliary) - rust-lang/rust#144251 (rustc-dev-guide subtree update) - rust-lang/rust#144254 (opt-dist: make `artifact-dir` an absolute path for `opt-dist local`) r? `@ghost` `@rustbot` modify labels: rollup
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This fixes the problems discovered by @theemathas in #142789:
Both boil down to the same issue: the TypeId "allocation" has a guaranteed 0 base address, but const-eval assumes it was non-zero (like normal allocations) and Miri randomized it (like normal allocations).
r? @oli-obk