C ++代码抛出段。 故障

Question

I have a C++ code as follow:

tryIt.h file

class tryIt : public someOtherClass
{
public:
       bool insertI ();
private:
       CommandI* m_pInsertI;
       bool createInsertI();
}

tryIt.cpp file

tryIt ::tryIt () : m_pInsertI(NULL)
{
    createInsertI();
}

tryIt ::~tryIt ()
{
   if(m_pInsertI!=NULL)
   {
      delete m_pInsertI;
      m_pInsertI=NULL
   }
}
bool createInsertI()
{
    m_pInsertI = returnFromSomeOtherFunction();
    return true;
}

bool insertI()
{
    // Over here if I use m_pInsertI anyhow my code fails with seg fault
    // even checking if(m_pInsertI==NULL) make the code throw seg fault
}

So the issue is touching m_pInsertI anywhere make my code throw Seg. fault (Signal 11). Even debugged the code with GDB but didn't got any useful info.

Compiler is GCC

Please help.

Answer 1

Sounds like the instance of this class does not exist or damaged. That is why you can't access any of its members and even if(m_pInsertI==NULL) check raises the exception.

Answer 2

in tryIt.cpp shouldn't

bool createInsertI()

be

bool tryIt::createInsertI()

same with insertI()

Answer 3

I see the following two possibilities :

• returnFromSomeOtherFunction() already returns a corrupted pointer
• You are copying your instance using the compiler generated methods (see example below)

Example (Rule of three violation)

tryIt instance1; // allocates instance2.m_pInsertI

{
    tryIt instance2;
    instance1 = instance 2; // performs a shallow copy

} // here, instance2.m_pInsertI is deleted

instance1.insertI(); // access violation

Recommendation:

Whether or not this is cause your problem: Do not implement manual memory management. Simply use a std::unique_ptr<CommandI> for m_pInsertI instead, so you do not need to implement the destructor or copy constructors/operators.