problem with double variable in s-function builder

Hello I try to build a simple s-function builder whit this code :

double m[30];  //u0[],y0[] is a double

for(i=0;i<=30;i++) 
  m[i]=u0[i];

for(i=0;i<=30;i++)
  y0[i]=m[i];

build are ok, but when run simulink model Matlab R2012a shut down without any other information so if I define

int m[30];

instead of

double m[30];

I no have problem, but I haven't a right result what is the error? thanks