where am I wrong in this SIMPLE code in an embedded matlab function?

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max 2013-3-18

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https://ww2.mathworks.cn/matlabcentral/answers/67620-where-am-i-wrong-in-this-simple-code-in-an-embedded-matlab-function

Hi, I've written a simple matlab function which calculate the roots of a polynomial function. It takes in input the coefficients of the polynomials, and gives in output the four values of the roots of x (x_1, x_2, x_3, x_4). The function works well in matlab, but when I put it in an embedded matlab function, it doesn't work, and I don't know the reasons.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
function [x_1,x_2,x_3,x_4] = fcn(b,c,d,e)
%#codegen
A1=b;
A2=c;
A3=d;
A4=e;
xr_0=-2.3*A4/A3;
toll=10^(-15);
nmax=1000;
xr= (3*xr_0^4+2*A1*xr_0^3+A2*xr_0^2-A4)/(4*xr_0^3+3*A1*xr_0^2+2*A2*xr_0+A3);
kk=0;
kz=xr-xr_0;
kz1=sqrt(kz);
  while ((kz1>toll) && kk<nmax)
      kk=kk+1;
      xr_0=xr;
      xr=  (3*xr_0^4+2*A1*xr_0^3+A2*xr_0^2-A4)/(4*xr_0^3+3*A1*xr_0^2+2*xr_0*A2+A3);
  end
  x_1=xr;
  k=xr;
  B1=k+b;
  B2=B1*k+c;
  B3=B2*k+d;
  xr_0= -2.3*B3/B2;
  xr= (2*xr_0^3+B1*xr_0^2-B3)/(3*xr_0^2+2*B1*xr_0+B2);
kk=0;
  while (abs(xr-xr_0))>toll && kk<nmax
      kk=kk+1;
      xr_0=xr;
       xr= (2*xr_0^3+B1*xr_0^2-B3)/(3*xr_0^2+2*B1*xr_0+B2);
  end
  x_2=xr;
  k=xr;
  C1=k+B1;
  C2=C1*k+B2;
  x_3=(-C1+sqrt(C1^2-4*C2))/2;
  x_4=(-C1-sqrt(C1^2-4*C2))/2;
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%