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• As an argument to non-member functions swap(), operator>>(), and getline().
• As an argument to basic_string::swap().
• Calling data() and c_str() member functions.

• Wiki Markup
  Calling non-const member functions, except {{operator\[\]()}}, {{at()}}, {{begin()}}, {{rbegin()}}, {{end()}}, and {{rend()}}.

• Wiki Markup
  Subsequent to any of the above uses except the forms of {{insert()}} and {{erase()}} which return iterators, the first call to non-const member functions {{operator\[\]()}}, {{at()}}, {{begin()}}, {{rbegin()}}, {{end()}}, or {{rend()}}.

Non-Compliant Example

The following non-compliant example copies the null-terminated byte string input into the string email, replacing ';' characters with spaces. This example is non-compliant because the iterator loc is invalidated after the first call to insert(). The behavior of subsequent calls to insert is undefined.

char input[] = "bogus@addr.com; cat /etc/passwd";
string::iterator loc;
string email;

// copy into string converting ";" to " "
for (size_t i=0; i <= strlen(input); i++) {
  if (input[i] != ';') {
    email.insert(loc++, input[i]);
  }
  else {
    email.insert(loc++, ' ');
  }
} // end string for each element in NTBS

Compliant Solution

In the following compliant solution, the value of the iterator loc is updated as a result of each call to insert so that the insert() method is never called with an invalid iterator. The updated iterator is then incremented at the end of the loop.

char input[] = "bogus@addr.com; cat /etc/passwd";
string::iterator loc;
string email;

// copy into string converting ";" to " "
for (size_t i=0; i <= strlen(input); i++) {
  if (input[i] != ';') {
    loc = email.insert(loc, input[i]);
  }
  else {
    loc = email.insert(loc, ' ');
  }
  ++loc;
} // end string for each element in NTBS	

Non-Compliant Example

Compliant Solution

The relationship between size and capacity makes it possible to predict when a call to a non-const member function will cause a string to perform a reallocation. This in turn makes it possible to predice when an insertion will invalidate references, pointers, and iterators (to anything other than the end of the string).

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