C and C++

LANG.TYPE.MI.PROTI : Multiple Inheritance with Protected Interface Class

Summary

A class inherits from multiple base classes, and one of those base classes is an interface class that is inherited with protected.

A class C is considered an interface class if either of the following is true.

See also:

Properties

Class Name Multiple Inheritance with Protected Interface Class
Significance style
Mnemonic LANG.TYPE.MI.PROTI
Categories
JSF++ JSF++:88 Multiple inheritance shall only be allowed in the following restricted form: n interfaces plus m private implementations, plus at most one protected implementation.
Availability Available for C++ only (not C).
Enabling Checks for this warning class are disabled by default, and require the unnormalized C ASTs for the project. To enable them, add the following WARNING_FILTER rule and RETAIN_UNNORMALIZED_C_AST specification to the project configuration file. 
RETAIN_UNNORMALIZED_C_AST = Yes
WARNING_FILTER += allow class="Multiple Inheritance with Protected Interface Class"
Note that retaining the unnormalized ASTs will increase the disk space used to store the project representation, and may make the analysis take longer.

Example 

// interface0 is always considered an interface class:
// - It has at least one method.
// - All methods are pure virtual.
// - It has no more than one scalar data member.
class interface0 {
  public:
    char *id;
    virtual void start(void) = 0;
};

// An instantiation of mix0 is considered an interface class in
// contexts where it is inherited as a "mixin" - that is, where at
// least one instantiation parameter is the interiting class.
template <class T>
class mix0 {
  public:
    void go(T){};
};

// This class is not an interface.
// - It has no methods.
// - It isn't a template, so can't be inherited as a mixin.
class noninterface {};

class derivedA : // 'Multiple Inheritance with Protected Interface Class' warning issued here
    protected interface0,
    protected mix0<derivedA>         // template parameter is the inheriting class
{
    void start(void) {};
};


class derivedB : protected interface0 {};                     // not multiple inheritance

class derivedC: public interface0, protected noninterface {}; // no protected interface

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.