Bug 281917 – WTF::StringImpl::createSubstringSharingImpl() should use std::span instead of pointer math

• Status: RESOLVED
• Resolution: FIXED
• Component: Web Template Framework

[David Kilzer (:ddkilzer)]

WTF::StringImpl::createSubstringSharingImpl() should use std::span instead of pointer math.

Code like this avoids bounds checks:

```
        if (substringSize >= allocationSize<LChar>(length))
            return create(std::span { rep.m_data8 + offset, length });
```

Found by std::span clang static analysis checker under development.

[Radar WebKit Bug Importer]

<rdar://problem/138429112>

[David Kilzer (:ddkilzer)]

Pull request: https://github.com/WebKit/WebKit/pull/35581

[EWS]

Committed 285581@main (e36a18c89230): <https://commits.webkit.org/285581@main>

Reviewed commits have been landed. Closing PR #35581 and removing active labels.