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Do not use an invalidated reference, pointer, or iterator because doing so results in undefined behavior.

This  This rule is a specific instance of CTR51-CPP. Use valid references, pointers, and iterators to reference elements of a container.

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This noncompliant code example copies input into a std::string, replacing semicolon (;) characters with spaces. This example is noncompliant because the iterator loc is invalidated after the first call to insert(). The behavior of subsequent calls to insert() is undefined.

#include <string>
 
void f(const std::string &input) {
  std::string email;
  std::string::iterator loc = email.begin();

  // Copy input into email converting ";" to " "
  for (auto I = input.begin(), E = input.end(); I != E; ++I, ++loc) {
    email.insert(loc, *I != ';' ? *I : ' ');
  }
}

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Using an invalid reference, pointer, or iterator to a string object could allow an attacker to run arbitrary code.

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