What is the lifetime of the result of std::string::c_str()?

user_279259 0
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In one of my programs, I have to interface with some legacy code that works with const char*.

Lets say I have a structure which looks like:

struct Foo
{
  const char* server;
  const char* name;
};

My higher-level application only deals with std::string, so I thought of using std::string::c_str() to get back const char* pointers.

But what is the lifetime of c_str() ?

Can I do something like this without facing undefined behavior ?

{
  std::string server = "my_server";
  std::string name = "my_name";

  Foo foo;
  foo.server = server.c_str();
  foo.name = name.c_str();

  // We use foo
  use_foo(foo);

  // Foo is about to be destroyed, before name and server
}

Or am I supposed to immediately copy the result of c_str() to another place ?

Thank you.

c-strings c-str lifetime c++ string
7 Answers

For completeness, here's a reference and quotation from cppreference.com:

The pointer obtained from c_str() may be invalidated by:

  • Passing a non-const reference to the string to any standard library function, or
  • Calling non-const member functions on the string, excluding operator[], at(), front(), back(), begin(), rbegin(), end() and rend().
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