[masspro]

Why downvotes? Ignoring C++11 changes for a minute, c_str is absolutely able to cause a reallocation if it needs to, such that after it returns, its return value and the value of data() are the same. Ergo no, the GP statement alone doesn’t imply anything.

[dpassens]

But the return value guarantee is, as far as I can see, a C++11 change, so you can't ignore those. And as of C++11, c_str is noexcept, so it cannot allocate anything.

[dataflow]

Please see my edit.