66d049cdad
This PR fixes a bug in `std::mersenne_twister_engine::seed(_Sseq&)` where the initialization twist is bypassed when the vectorized engine optimization (`_LIBCPP_ABI_VECTORIZED_MERSENNE_TWISTER_ENGINE`) is enabled. In the vectorized implementation introduced in #206423, the engine state must be pre-twisted during initialization by calling `__update_all_states()` at the end of the `seed` functions. However, in `seed(_Sseq& __q)`, the all-zero state check contains an early `return;` when a non-zero state is verified. This early return bypasses the trailing `__update_all_states()` call. Consequently, the generator is initialized with raw, untwisted seed values (tempered) rather than the standard twisted values. This only manifests when compiled with unstable ABI settings (`_LIBCPP_ABI_VERSION >= 2`) which enables the vectorized implementation. I replaced the early `return;` inside the all-zero state verification block with a loop break, and conditionalized the zero-state fix using the loop index `__i`, ensuring `__update_all_states()` is always executed at the end of the function. Added regression tests to `seed_sseq.pass.cpp` asserting the exact deterministic outputs for both 32-bit and 64-bit engines. |
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| flang | ||
| flang-rt | ||
| libc | ||
| libclc | ||
| libcxx | ||
| libcxxabi | ||
| libsycl | ||
| libunwind | ||
| lld | ||
| lldb | ||
| llvm | ||
| llvm-libgcc | ||
| mlir | ||
| offload | ||
| openmp | ||
| orc-rt | ||
| polly | ||
| runtimes | ||
| third-party | ||
| utils | ||
| .clang-format | ||
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| .clang-tidy | ||
| .git-blame-ignore-revs | ||
| .gitattributes | ||
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| .mailmap | ||
| CODE_OF_CONDUCT.md | ||
| CONTRIBUTING.md | ||
| LICENSE.TXT | ||
| pyproject.toml | ||
| README.md | ||
| SECURITY.md | ||
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