<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/61013>61013</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            std::string unnecessarily maintains a null terminated char array all the time.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++,
            performance
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          hiraditya
      </td>
    </tr>
</table>

<pre>
    This is probably out of convenience to simplify `data()` or `c_str()`. There is no need to maintain a null terminated char-array inside std::string. Because of this all the operations that increase the size of string has a redundant operation that adds a null-byte at the end of the string.

e.g., insert, push_back

```cpp
basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, value_type __c)
{
...
 traits_type::assign(__p[__ip], __c);
    traits_type::assign(__p[++__sz], value_type()); // extra assignment
```

for push_back
```cpp
void
basic_string<_CharT, _Traits, _Allocator>::push_back(value_type __c)
{
...
 traits_type::assign(*__p, __c);
    traits_type::assign(*++__p, value_type()); // extra assignment
```

This extra assignment hurts performance. For example `std::getline` calls `string::push_back` for each character [https://github.com/llvm/llvm-project/issues/21566]
</pre>
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