[libcxx-commits] [libcxx] [libc++] Fix erroneous internal capacity evaluation in vector<bool> (PR #120577)

[A. Jiang via libcxx-commits]

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@@ -115,7 +115,7 @@ class _LIBCPP_TEMPLATE_VIS vector<bool, _Allocator> {
   }
   _LIBCPP_HIDE_FROM_ABI _LIBCPP_CONSTEXPR_SINCE_CXX20 static size_type
   __external_cap_to_internal(size_type __n) _NOEXCEPT {
-    return (__n - 1) / __bits_per_word + 1;
+    return (__n + __bits_per_word - 1) / __bits_per_word;
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frederick-vs-ja wrote:

I guess we should handle the case where `__n + __bits_per_word - 1` wraps (and thus `(__n + __bits_per_word - 1) / __bits_per_word` becomes zero).

https://github.com/llvm/llvm-project/pull/120577