| commit | 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff | [log] [tgz] |
|---|---|---|
| author | Vitaly Buka <vitalybuka@google.com> | Thu May 02 14:26:38 2024 -0700 |
| committer | llvmbot <60944935+llvmbot@users.noreply.github.com> | Sat Jun 15 10:21:32 2024 -0700 |
| tree | 157e69d5386f911eaba3ed8b03abccadb65cdf38 | |
| parent | 72c9425a79fda8e9001fcde091e8703f9fb2a43a [diff] |
[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)
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