Is `&s[0]` a Safe and Contiguous Pointer to Characters in a C std::string?

Can "&s[0]" Reference Consecutive Characters in a std::string?

It has been noticed that code like this:

std::string s;
s.resize( strLength );
memcpy( &s[0], str, strLength );

would be safe if s was a std::vector, but the question is whether it is a safe use of std::string.

In C 98/03, a std::string's allocation is not guaranteed to be contiguous. However, C 11 enforces this contiguity. In practice, most implementations use contiguous storage.

The use of &s[0] is guaranteed by the C 11 standard to work, even for zero-length strings. This is because the operator[] is defined as:

Returns *(begin() + pos) if pos < size(), otherwise a reference to an object of type T with value charT(); the referenced value shall not be modified

Additionally, data() is defined as:

Returns: A pointer p such that p + i == &s[i] for each i in [0,size()].

Therefore, "&s[0]" points to consecutive characters in a std::string and is a safe usage.

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