Author: Vitaly Buka Date: 2024-06-15T10:21:32-07:00 New Revision: 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff
URL: https://github.com/llvm/llvm-project/commit/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff DIFF: https://github.com/llvm/llvm-project/commit/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff.diff LOG: [libcxx] Align `__recommend() + 1` by __endian_factor (#90292) This is detected by asan after #83774 Allocation size will be divided by `__endian_factor` before storing. If it's not aligned, we will not be able to recover allocation size to pass into `__alloc_traits::deallocate`. we have code like this ``` auto __allocation = std::__allocate_at_least(__alloc(), __recommend(__sz) + 1); __p = __allocation.ptr; __set_long_cap(__allocation.count); void __set_long_cap(size_type __s) _NOEXCEPT { __r_.first().__l.__cap_ = __s / __endian_factor; __r_.first().__l.__is_long_ = true; } size_type __get_long_cap() const _NOEXCEPT { return __r_.first().__l.__cap_ * __endian_factor; } inline ~basic_string() { __annotate_delete(); if (__is_long()) __alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap()); } ``` 1. __recommend() -> even size 2. `std::__allocate_at_least(__alloc(), __recommend(__sz) + 1)` - > not even size 3. ` __set_long_cap() `- > lose one bit of size for __endian_factor == 2 (see `/ __endian_factor`) 4. `__alloc_traits::deallocate(__alloc(), __get_long_pointer(), __get_long_cap())` -> uses even size (see `__get_long_cap`) (cherry picked from commit d129ea8d2fa347e63deec0791faf389b84f20ce1) Added: Modified: libcxx/include/string Removed: ################################################################################ diff --git a/libcxx/include/string b/libcxx/include/string index 618ceb71b26b4..56e2ef09947f4 100644 --- a/libcxx/include/string +++ b/libcxx/include/string @@ -1943,10 +1943,10 @@ private: if (__s < __min_cap) { return static_cast<size_type>(__min_cap) - 1; } - const size_type __boundary = sizeof(value_type) < __alignment ? __alignment / sizeof(value_type) : 1; + const size_type __boundary = sizeof(value_type) < __alignment ? __alignment / sizeof(value_type) : __endian_factor; size_type __guess = __align_it<__boundary>(__s + 1) - 1; if (__guess == __min_cap) - ++__guess; + __guess += __endian_factor; return __guess; } _______________________________________________ llvm-branch-commits mailing list llvm-branch-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-branch-commits
