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class S { 
  int v; 
 
public: 
  S() : v(12) {} // Non-trivial constructor 
 
  void f(); 
};   
 
void f() { 
 
  // ...   
 
  goto bad_idea;   
 
  // ... 
 
  S s; // Control passes over the declaration, so initialization does not take place.   
 
  bad_idea: 
    s.f(); 
}

Compliant Solution

This compliant solution ensures that s is properly initialized prior to performing the local jump.

class S { 
  int v; 
 
public: 
  S() : v(12) {} // Non-trivial constructor 
  
  void f(); 
};   
 
void f() { 
  S s; 
 
  // ... 
 
  goto bad_idea; 
 
  // ... 
 
  bad_idea: 
    s.f(); 
}

Noncompliant Code Example

In this noncompliant code example, f() is called with an iterable range of objects of type S. These objects are copied into a temporary buffer using std::copy(), and when processing of those objects is complete, the temporary buffer is deallocated. However, the buffer returned by std::get_temporary_buffer() does not contain initialized objects of type S, so when std::copy() dereferences the destination iterator, it results in undefined behavior because the object referenced by the destination iterator has yet to start its lifetime. This is because , while space for the object has been allocated, no constructors or initializers have been invoked.

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Referencing an object outside of its lifetime can result in an attacker being able to run arbitrary code.

Automated Detection

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

Bibliography

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