[libcxx-commits] [libcxx] [libc++] Fix vector::append_range growing before the capacity is reached (PR #183264)

[Louis Dionne via libcxx-commits]

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ldionne wrote:

```suggestion
    { // Ensure no reallocation happens, and that we don't invalidate iterators.
```

And then also ensure that `.data()` is stable.

https://github.com/llvm/llvm-project/pull/183264