Will std::string always be null-terminated in C++11?

c++ string c++11 language-lawyer null-terminated
links77 picture links77 · May 20, 2011 · Viewed 9.2k times · Source

In a 2008 post on his site, Herb Sutter states the following:

There is an active proposal to tighten this up further in C++0x and require null-termination and possibly ban copy-on-write implementations, for concurrency-related reasons. Here’s the paper: http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2008/n2534.html . I think that one or both of the proposals in this paper is likely to be adopted, but we’ll see at the next meeting or two.

I know that C++11 now guarantees that the std::string contents get stored contiguously, but did they adopt the above in the final draft?

Will it now be safe to use something like &str[0]?

Answer

James McNellis picture James McNellis · May 20, 2011

Yes. Per the C++0x FDIS 21.4.7.1/1, std::basic_string::c_str() must return

a pointer p such that p + i == &operator[](i) for each i in [0,size()].

This means that given a string s, the pointer returned by s.c_str() must be the same as the address of the initial character in the string (&s[0]).

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