CERT C++: EXP60-CPP

The issue occurs when you pass an object with a non-standard layout type across an application binary interface (ABI). Differences in layout across an ABI might result in unsafe or unpredictable code execution.

Polyspace reports a violation when you pass an object with a non-standard layout to a function that is not part of the std:: or boost:: libraries and that function is defined in a different translation unit (source file).

Polyspace does not report a violation of this rule when you pass an object with non-standard layout to:

If you pass an object with a non-standard layout across an execution boundary and you do not check whether the object has the same layout on both sides of the execution boundary, your code might have correctness and portability issues.

If the object has a different layout on each side of the execution boundary, the code execution might result in undefined behavior, incorrect results, or incompatibilities that are difficult to diagnose.

Pass objects with a standard layout when you have code that interacts across an execution boundary. If you pass an object with a non-standard layout across an execution boundary, check that both sides of the boundary follow the same ABI. Different code components follow the same ABI if the components are:

#include <iostream>
#include <string>

class Roster // Non-Standard Layout class
{
public:
   Roster(std::string name) : student(name) {}
   std::string getName() const { return student; }

private:
   std::string student;
   virtual void someFunc() {}
};

extern void PrintRoster(Roster *);

void func()
{
   Roster roster("John Doe");
   PrintRoster(&roster); //Noncompliant
}

In this example, an object of type Roster is passed to the function PrintRoster() which is defined in a separate translation unit.

Polyspace considers that the program crosses an execution boundary to interact with the implementation of the function PrintRoster() and reports a violation of the coding rule since there is no guarantee that object roster has the same layout on the other side of the execution boundary. The code execution might result in unexpected behavior.

The class Roster has a non-standard layout because it has a virtual member function someFunc().