Peng Liu a5b3d3a03f
[libc++] Fix {std, ranges}::copy for vector<bool> with small storage types (#131545)
The current implementation of `{std, ranges}::copy` fails to copy
`vector<bool>` correctly when the underlying storage type
(`__storage_type`) is smaller than `int`, such as `unsigned char`,
`unsigned short`, `uint8_t` and `uint16_t`. The root cause is that the
unsigned small storage type undergoes integer promotion to (signed)
`int`, which is then left and right shifted, leading to UB (before
C++20) and sign-bit extension (since C++20) respectively. As a result,
the underlying bit mask evaluations become incorrect, causing erroneous
copying behavior.

This patch resolves the issue by correcting the internal bitwise
operations, ensuring that `{std, ranges}::copy` operates correctly for
`vector<bool>` with any custom (unsigned) storage types.

Fixes #131692.
2025-03-19 11:55:51 -04:00
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