分割錯誤的原因； 函數調用后指針值丟失

Question

調用函數“ flightdynamics”后出現分段錯誤錯誤。 指針“ impulsevecnorm”似乎“松散”了它的值（即，如果我嘗試訪問它所指向的元素，則會遇到分段錯誤錯誤）。 如果我將'impulsevecnorm'傳遞給函數'flightdynamics'，我可以在return語句之前打印出它的值，但是在return之后，返回main（），它將失去它的值。 這很奇怪，因為在“飛行動力學”中我沒有明確地訪問或更改“ impulsevecnorm”的值，因此我不明白為什么它以后應該“失去”它的價值。 這是代碼：

int main()
{

double *currstate, *nextstate;
  double *impulsevecnorm;

 /* Start a few for loops */
              srand(time(NULL));

          currstate = initialize (vx0, vy0);
          impulsevecnorm = impulsecalc (currstate);
          for (i=0; i<NBALLS; i++)
            {
                double terrain[(int) (NSTEPS*2)] = {0};
                double terrainsl[(int) (NSTEPS*2)] = {0};

                  for (j=0; j<NSTEPS; j++)
                  {

                  printf("%f \n",impulsevecnorm[1]); // At this point it prints fine
                  nextstate = flightdynamics (currstate, terrain, terrainsl, bcounter, tcounter);
                  printf("%f \n",impulsevecnorm[1]); // here i get a segmentation fault and the code stops running
                  ..... 
                  /* to end of function (rest doesn't matter as error appears before this)*/
}}}

double * flightdynamics (double *state, double terrain[], double terrainsl[], double counter, int endterr)
{                                                                                      
    double *out = (double *)malloc ( (NSTATE+3)*sizeof(double) );
    double *hit = (double *)malloc ( 3*sizeof(double) );
    double tx[sizet] = {0}, theight[sizet] = {0};

    for (j = 0; j < sizet; j++)
    {
        tx[j] = ((double) endterr/refine + (double) j)*space;
        theight[j] = randomground();
    }

    gsl_interp_accel *acc = gsl_interp_accel_alloc();
    gsl_spline *spline = gsl_spline_alloc(gsl_interp_akima, sizet);
    gsl_spline_init(spline, tx, theight,sizet);

    for (i = (int) endterr; i< (int) endterr + (int) ((sizet-1)*refine/space); i++)
    {
        terrain[i] = gsl_spline_eval(spline,xi,acc);
        terrainsl[i] = gsl_spline_eval_deriv(spline,xi,acc);
        xi = xi+(double) space/refine;
    }

    newendterr = endterr + sizet*refine/space;

     hit = intersect(vylift,vxlift,xlift,ylift,terrain,(int) (xlift*refine/space),newendterr);

    landx = hit[0];
    thland = terrainsl[(int) (landx*(double)refine/space)];
        out[0] = hit[1]; /*xland */
        out[1] = hit[2]; /*yland  */
        tflight = (out[0] - xlift)/vxlift;
        out[3] = vylift - g*tflight; /* vyland */
      out[2] = vxlift; /* vxland */
      out[4] = philift + wlift*tflight; /* philand */
      out[5] = wlift; /* wland */
      out[6] = thland;
      out[7] = landx;
      out[8] = (double) newendterr;

// if I pass impulsevecnorm to this function I can still print out it's value using printf here

 return out;
}

double* intersect (double vy, double vx, double currx, double curry, double terrainy[], int counter, int endterr)
{
    double* out = (double *)malloc ( 3*sizeof(double) );
    out[0]=-1;

for (i = counter+1; i < endterr + (sizet-1)*refine; i++)
{
    xball = (double) i*deltax;

    for(j=start; j<endl; j++)
    {
        xt = (double) j*deltax;
        if (pow(xball-xt,2)+pow((vx*vy*(xball-currx)-g*pow(xball-currx,2)+vx*vx*(curry-terrainy[j]))/(vx*vx),2)<= (double) (rball*rball) && j!=counter)
        {
            out[0] = xt;
            out[1] = xball;
            out[2] = (vx*vy*(xball-currx)-g*pow(xball-currx,2)+vx*vx*curry)/(vx*vx);
            flag = 1;
            break;
        }
    }
    if (flag == 1)
    {
        break;
    }
}
return out;
}

double * impulsecalc (double *state)
{
  double *out1 = (double *)malloc ( ((int)(NSTATE/2)) * sizeof(double) );
    out1[0]= (1 - rt)*state[2] - rball*rt*state[5] +
            rball*(MI*state[5] + m*rball*((-1 + rt)*state[2] + rball*rt*state[5]))/
            (MI + m*rball*rball);
    out1[1]= (1 - rn)*state[3];
    out1[2]= state[5] - (MI*state[5] + m*rball*((-1 + rt)*state[2] + rball*rt*state[5]))/
            (MI + m*rball*rball);
  return out1;
}

為了使代碼更短，我省略了除指針定義之外的所有變量定義。 相信所有其他變量均已正確定義。 函數flydynamics和intersect很長，但是為了簡潔起見，我不想隱藏任何代碼，以防錯誤源也被排除在外。

我是一個業余程序員。 僅在最近才開始使用C。 任何幫助，將不勝感激。

Answer 1

多謝你們。 問題出在terrain和terrainsl陣列中。 我用很少的空間初始化了它們。 飛行動力學函數中的for循環超出數組范圍。

Answer 2

您正在寫方法中的state[4] 。 如果state元素少於5個，則您正在寫入另一個內存位置，該位置可能是impulsevecnorm 。

沒有任何指示的是什么initialize (vx0, vy0); 可能會返回，我猜想它返回的元素少於5個。