[Mingw-users] String runtime error

[Matt F. <mat...@pr...>]

Sorry about the HTML.  Hopefully, this will work better.  (I've 
edited my original post a little, because I noticed a couple things 
which are unclear).

Thanks again for any help you can provide.

Sincerely,
Matt Fiedler

To whom it may concern:

I'm working on a simple ecology simulation which manipulates objects 
called Organisms.  Each organism has a number of characteristics.  
The one most relevant to my problem is a string containing the 
Organism's species name.

In the course of the simulation, the program often invokes an 
Organism copy constructor/constructor for the purpose of 
reproduction.  The exact constructor invoked depends on the type of 
reproduction taking place.  After the constructor is called for 
either the second or the third time, a segmentation fault results.  
Using the Insight debugger, I have discovered that the error comes 
inside string member functions (i.e. it fails while trying to copy 
the string).  The odd thing is that the constructor works without 
problems several times before it crashes with identical input.  

I have checked the input data (i.e. the old string from which I am 
trying to construct the new string in the new organism) using the 
debugger and found it to be normal and uncorrupted in any way.  I'm 
puzzled as to why the program is crashing while doing something as 
simple as initializing one string from another.
 
I'm pasting the header file of the Organism class and the 
implementation of the problem constructor into this post.  If any 
other code or information would be useful, I'd be happy to provide 
it.  I'm running Mingw through Dev-C++ 5, beta 3.  The version of 
Mingw uses GCC 2.95.3-6.

Even if you can't find the exact solution, I'd appreciate it if you 
could tell me whether either of these two theories are at all 
plausible:

1) There is a problem in the way the Mingw string class allocates 
memory and this causes my segfault.
2) I'm mangling memory using pointers somewhere.  I don't know how 
this could happen because the pointers I use are inside handlers 
(shared_ptr's from the Boost library) that handle deletion.  The only 
other times I use pointers, I am very clearly initializing them to 
point to new storage.  Moreover, the segfaults don't happen randomly 
as if I was simply corrupting memory wily-nily. They always happen in 
the same place during the initialization of the same type of object).
3) Some third possibility (I consider this the most likely 
explanation, though I am at a loss as to what it would be).
 
Thank you very much for any help that you can provide.
 
Sincerely,
Matt Fiedler


First, a few typedefs to be aware of:

typedef matrix<OrgVector> WorldMatrix; /* defines "geographic" 
storage type
    an OrgMatrix is a vector of vectors of localities, all of the 
inside vectors will be
    maintained at the same size by means of the World constructor 
(matrix is a modified version of the STL
    */
typedef matrix<int> AbioticMatrix; /* allows defintion of an integer 
value for each
    location in the environment, for example of solar input*/

typedef boost::shared_ptr <ReproSys> ReproPtr; //Pointer to a 
reproductive system
typedef boost::shared_ptr <NutriSys> NutriPtr; //Pointer to a 
nutritional system

class Organism
{
    friend bool operator== (const Organism & lhs, const Organism & 
rhs);
    
    public:  
        //constructors  
        Organism (); //default constructor 
        Organism (const Organism & OldOrg); //copy constructor
        
        Organism (const Organism & OldOrg, const int & NewRow, const 
int & NewCol);  
        /* copy constructor with location initialization */
        
        Organism (const string & Name, const int & NewSize, const 
NutriPtr & ProtoNutri, const ReproPtr & ProtoRepro);
             /* allows initialization from the building blocks of an 
organism */
                    
        //accessors
        bool isAlive () const;  //indicates if the organism is alive
        string getName () const;
        int getRow () const;
        int getCol () const;
        ReproPtr getReproSys () const;
        NutriPtr getNutriSys () const;
        int getSize () const;
                      
        //life activity functions
        
        //functions to interface with the NutriSys class
        void Forage (AbioticMatrix & SolarInput, WorldMatrix & 
Environment); 
        void CheckNutrition ();
        
        //functions to interface with the ReproSys class       
        void Reproduce (WorldMatrix & Environment); 
        
        //functions for interfacing with other organisms
        int beEaten ();
        
        const Organism & operator= (const Organism & 
rhs);  //assignment
              
    private:
        
        //data members
        
        //organism body systems
        ReproPtr myReproSys;
        NutriPtr myNutriSys;
                
        //organism characteristics
        string SpeciesName;        
        bool Alive;
        int myRow, myCol, mySize;
};

A couple of notes about the above definition.  ReproPtr and NutriPtr 
are typdefs of the boost shared_ptr's.  They always initialize 
correctly inside the constructor intializer list, as do the other 
data members.

Organism::Organism (const Organism & OldOrg, const int & NewRow, 
const int & NewCol)
/*  Pre: an organism and two integers must be input
    Post: an organism idenctical to the old one except for its 
location has 
    been constructed */    
    : myNutriSys ((OldOrg.myNutriSys)->Clone()), //calls a clone 
function which returns a pointer to a new object of the 	
					//correct type (NutriSys and 
ReproSys are only base classes, different types 		
				//of systems inherit from them)
      myReproSys ((OldOrg.myReproSys)->Clone()),
      mySize (OldOrg.mySize),
      myRow (NewRow),
      myCol (NewCol),      
      Alive (OldOrg.Alive),
      SpeciesName (OldOrg.SpeciesName)  <-this seems to be the problem
{   
}

Organism::Organism (const Organism & OldOrg)
/*  Pre: an organism must be input
    Post: an organism idenctical to the old one has been constructed 
*/    
    : myNutriSys ((OldOrg.myNutriSys)->Clone()),
      myReproSys ((OldOrg.myReproSys)->Clone()),
      SpeciesName (OldOrg.SpeciesName),
      myRow (OldOrg.myRow),
      myCol (OldOrg.myCol),
      Alive (OldOrg.Alive),
      mySize (OldOrg.mySize)       
{ 
}

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