C++ vector push back crashes after object is pushed back and function exits

Question

The problem was a stupid error from another class accessing the vector and deleting iterators. Nothing to do with the code below. Sorry to waste your time.

I must be missing something elementary. I've got a function which creates an object, manipulates it's data and then pushes it into a vector. The moment the function exits, the program crashes with a SIGSEV, and I'm left staring at (Kdevelop gcc 4.5 gdb) :

   /**
   *  The dtor only erases the elements, and note that if the
   *  elements themselves are pointers, the pointed-to memory is
   *  not touched in any way.  Managing the pointer is the user's
   *  responsibility.
   */
  ~vector()
  { std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
          _M_get_Tp_allocator()); }

I am not storing pointers, I'm trying to store instantiated objects.

void Init::initIndividual(int ID, int gen)
{
  Individual temp_person = Individual(ID,gen);
  int inst_size = getRandom<int>(1,max_inst_size);
  for (int k=0;k<inst_size;k++)
  {
    retry:
    // (1) randomly choose a body part
    int body_num = getRandom<int>(1,20);
    body_part temp_part = get_body_part(body_num);
    // NOTE: We need to make sure that the body part is unique!
    std::vector<Instruction> already_existing = temp_person.get_instructions();
    if (already_existing.size() > 0)
    {
      for (int a=0; a< already_existing.size();a++)
      {
       std::string name = already_existing[a].get_body_part();
       if ( name.compare(temp_part.name) == 0 )
       { //if body part already exists in the list, retry!
         goto retry;
       }
      }
    }    
    // (2) Create a new Instruction for this body part
    Instruction temp_inst = Instruction(temp_part.name,temp_part.max_angle,temp_part.min_angle);
    // (3) Randomly pick a number of body parameters to use
    int paramsize = getRandom<int>(1,max_params_size);
    // (4) Randomly choose time and degree trajectory parameters for this body part and append!
    for (int x=0;x < paramsize; x++)
    {
     float time = 0.0f;
     int choice = 0;
     // (4.a) If begin of body parameters
     if (x==0)
     {
   //if always start at time = 0
   if (static_time_init)
   {
     time = 0.0f;
   }
   //if randomly choose the init time
   else if (!static_time_init)
   {
     time = getRandom<float>(0.0f,(float)(time_constrain-1));
   }
     }
     // (4.b) if not @ start of params
     else if(x!=0)
     {
       redo:  
       float previous_time = temp_inst.parameters.back().time; //get previous time
       double incrementor = getRandom<double>(0.1,1.0); //increment time by min 0.1 max 1.0
       time = previous_time + (float)incrementor;
       if (time > time_constrain) //if current time is more than time constrain, redo
       { 
        goto redo;
       }
     }
     // (5) Randomly pick a degree to move to (within body part constrains)
     float degree = getRandom<float>(temp_inst.get_min_angle(),temp_inst.get_max_angle());
     Parameter foo = Parameter(time,degree);
     temp_inst.add_parameter(Parameter(time,degree));
   }
  temp_person.add_Instruction(temp_inst);
  }
  temp_person.endtime = time_constrain;
 }

That is the entire function.

 std::vector<Individual> population;

Doesn't the push_back function copy the object when pushing it back ? Is the destructor invoked because push_back is trying to destroy temp_person ? I have not defined a copy operator in class Individual. I have run into this problem before and never figured it out. Does this happen because at the end of the function temp_person is out of scope ? Thank you !

Edit: Class Individual

class Individual 
{
   friend class Population;
   friend class Crossover;
   friend class Init;
 private:
   std::string xml_file;
   char *arg4;
 protected:
   bool saved, mutated, dead;
   unsigned int UID, generation;
   int executions;
   std::vector<Instruction> instructions;
   int father_UID, mother_UID;
   double eta,endtime;
 public:
   int uniform;
   float fitness;
   pthread_mutex_t thread_mutex;
   //Some other functions irrelevant

Please note, that the vector of instructions has another vector of structs.

class Instruction 
{
  friend class Crossover;
 private:  
  unsigned int param_size;
  float max_angle, min_angle;
  bool micro_mutated;
 public:
  std::string body_part;
  std::vector<Parameter> parameters;
  //other stuff

class Parameter
{
  public:
   float time;
   float degree;
   Parameter(float t,float d);
};

Nothing crazy here.

Could this be a problem of a shallow copy obtained by the population.push_back ?

Answer 1

pthread_mutex_t thread_mutex;

Copying a pthread_mutex_t is not meaningful. I'd wager that's part of the problem. I have suspicions about your char* too; who owns it?

---

My justification as to why I believe pthread_mutex_t can't be copied: the only documented way to obtain an initialized mutex is from using pthread_mutex_init. Additionally, all the pthread_mutex_* functions manipulate mutexes using pass-by-pointer (unlike e.g. pthread_thread_t).

Answer 2

Doesn't the push_back function copy the object when pushing it back ? 

Yes, it does.

Is the destructor invoked because push_back is trying to destroy temp_person?

No, it is not. It is called because the temp object is destroyed at the end of the function.

I have not defined a copy operator in class Individual. 

Let us see the declaration of the class.

Does this happen because at the end of the function temp_person is out of scope ?

Yes, the temp object is destroyed, but if the class is OK, this should not be a problem. Again - we need to see the code.

I bet it's something with the constructor/destructor (:

By the way, is population global? Outch!