Structures with pointers

Question

so I have a structure called Shield that has three pointers in it. I need to fill up with data one of this pointers before hand and I need to access this data inside of a constant loop. The problem that I'm having is that whenever I try and access what should be in my pointers my program crashes. This is my structure

struct Shield{
  esat::Vec3 *circle;
  esat::Vec2 *walls;
  bool *isActive;
};

where esat::Vec3 and esat::Vec2 are just structures with floats representing vectors.

I initialize my pointers inside of a function that takes as a parameter an Shield object and fill up such pointer data that I need.

void InitShield(Shield shield){

  shield.circle = (esat::Vec3*) malloc((KVertices + 1) * sizeof(esat::Vec3));
  shield.walls = (esat::Vec2*) malloc((KVertices + 1) * sizeof(esat::Vec2));
  shield.isActive = (bool*) malloc((KVertices + 1) * sizeof(bool));

  float angle = 6.28f / KVertices;
  for(int i=0; i<KVertices; ++i){
    (*(shield.circle + i)).x = cos(angle * i);
    (*(shield.circle + i)).y = sin(angle * i);
    (*(shield.circle + i)).z = 1.0f;
    (*(shield.isActive + i)) = true;
  }

}

And then I try and get access to what I supposedly stored in my pointer.

void DrawCircle(esat::Mat3 base, esat::Vec2 *tr_points, esat::Vec3 *circle, bool *checkActive){

  CheckShield(first_shield);
  for(int i=0; i<KVertices; ++i){
    esat::Vec3 points = esat::Mat3TransformVec3(base, (*(circle + i)));
    *(tr_points + i) = {points.x, points.y};
  }

  for(int i=0; i<KVertices; ++i){
    if((*(checkActive + i)) == true){
      esat::DrawSetStrokeColor(color.r, color.g, color.b);
      esat::DrawLine((*(tr_points + i)).x, (*(tr_points + i)).y, (*(tr_points + ((i+1)%KVertices))).x, (*(tr_points + ((i+1)%KVertices))).y);
    }
  }

}

This is where my program crashes. When I try and access what should be inside my circle pointer the program fails to and crashes. Does anyone know what am I doing wrong? I haven't figured it out yet.

Answer 1

This function accepts an object of the type Shield by value.

void InitShield(Shield shield){

That is the function deals with a copy of the value of the passed argument.

Changing the copy within the function does not influence on the original object.

If you are using C++ then declare the function at least like

void InitShield(Shield &shield){

and use the operator new instead of calling malloc directly.

If you are using C then declare the function like

void InitShield(Shield *shield){

Also it is unclear why you are allocating KVertices + 1 objects as for example

shield.circle = (esat::Vec3*) malloc((KVertices + 1) * sizeof(esat::Vec3));

But the following for loop uses only KVertices iterations.

for(int i=0; i<KVertices; ++i){