[all-commits] [llvm/llvm-project] 72c942: [libc++][NFC] Rewrite function call on two lines f...

[Vitaly Buka via All-commits]

  Branch: refs/heads/release/18.x
  Home:   https://github.com/llvm/llvm-project
  Commit: 72c9425a79fda8e9001fcde091e8703f9fb2a43a
      https://github.com/llvm/llvm-project/commit/72c9425a79fda8e9001fcde091e8703f9fb2a43a
  Author: Louis Dionne <ldionne.2 at gmail.com>
  Date:   2024-06-15 (Sat, 15 Jun 2024)

  Changed paths:
    M libcxx/include/string

  Log Message:
  -----------
  [libc++][NFC] Rewrite function call on two lines for clarity (#79141)

Previously, there was a ternary conditional with a less-than comparison
appearing inside a template argument, which was really confusing because
of the <...> of the function template. This patch rewrites the same
statement on two lines for clarity.

(cherry picked from commit 382f70a877f00ab71f3cb5ba461b52e1b59cd292)


  Commit: 3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff
      https://github.com/llvm/llvm-project/commit/3b5b5c1ec4a3095ab096dd780e84d7ab81f3d7ff
  Author: Vitaly Buka <vitalybuka at google.com>
  Date:   2024-06-15 (Sat, 15 Jun 2024)

  Changed paths:
    M libcxx/include/string

  Log Message:
  -----------
  [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)


Compare: https://github.com/llvm/llvm-project/compare/443e23eed24d...3b5b5c1ec4a3

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