C++ heap corruption detected occurs while I try to use the function I made in derived class -

here comes code. firstly have defined 3 class

class matrix {protected: double *mdata; int rows,columns;

class polyg{protected: matrix x,y,z,centre;

class triangle: public polyg{protected:public: triangle(matrix x1,matrix y1,matrix z1){x=x1;y=y1;z=z1; centre=(x+y+z).change_scale(1/3); }

and have defined overloading function matrix multiplication such

matrix operator*(matrix &m) const{   if(columns!=m.getrows()) {       cout<<"invalid size!!"<<endl; exit(1);   }   matrix temp(rows,m.getcols());   for(int x=0; x<rows; x++) {       for(int y=0; y<m.getcols(); y++) {           double value = 0;           for(int z=0; z<columns; z++) {               value = value+(mdata[index(x+1,z+1)]*m.mdata[index(z+1,y+1)]);           }           temp.mdata[index(x+1,y+1)] = value;       }    }   return temp;} 

index function defined as

int index(int m, int n) const // return position in array of element (m,n){ if(m>0 && m<=rows && n>0 && n<=columns) return (n-1)+(m-1)*columns; else {cout<<"error: out of range"<<endl; exit(1);} 

}

and defined member function, overrides pure virtual function in polyg class, in triangle class such as

    void rotate(double angle){  double pi=4*atan(1.0); double angle_rad=pi*angle/180;  matrix m_rot(2,2); m_rot(1,1)=cos(angle_rad); m_rot(1,2)=sin(angle_rad); m_rot(2,2)=cos(angle_rad); m_rot(2,1)=-sin(angle_rad);//matrix of rotation of angle inserted  x=m_rot*x; y=m_rot*y; z=m_rot*z;//rotating triangle  } 

problem occurs from

x=m_rot*x; y=m_rot*y; z=m_rot*z; 

this part. heap corruption detected error occurs part. if remove part, code runs totally without problem.

also, if define in main

int main(){matrix a,b,c; c=a*b; 

it works totally also.

however if use function made in triangle class,for example,

triangle tri(a,b,c); tri.rotate(30); 

problem occurs

no errors occur before debugging after compile, heap corruption detected error occurs

could explain problem? , how fix it?

this code looks suspect me:

 for(int x=0; x<rows; x++) {       for(int y=0; y<m.getcols(); y++) {           double value = 0;           for(int z=0; z<columns; z++) {               value = value+(mdata[index(x+1,z+1)]*m.mdata[index(z+1,y+1)]);           }           temp.mdata[index(x+1,y+1)] = value; 

with z iterating on column indexes, pass value first argument index function (source no longer present in post) appears assume first argument row index.