question about compile_to_c code

[cery999]

the vectorize and parallel will missing after codegen to .cpp file
and when using g++ to compile it.

it throw
test_add.c:(.text+0x2075): undefined reference to `halide_error_host_is_null'

1 #include "Halide.h"
   2 #include <cstdio>
   3
   4 using namespace Halide;
   5
   6 int main(int argc, char **argv) {
   7     Target target = get_jit_target_from_environment();
   8     const int vec_width = target.natural_vector_size<float>();
   9     int W = vec_width;
  10     int H = 512;
  11     Buffer<float> a(H, W);
  12     Buffer<float> b(H, W);
  13     a.allocate();
  14     a.fill(0);
  15     b.allocate();
  16     b.fill(1);
  17     Var x, y;
  18     Func f;
  19     // c = a + b
  20     f(x, y) = a(x, y) + b(x, y);
  21     f.bound(x, 0, vec_width).vectorize(x);
  22     Buffer<float> c = f.realize();
  23
  24     f.compile_to_c("test_add.cpp",{a,b,c},"main");
  25     f.compile_to_header("test_add.h",{a,b,c},"main");
  26
  27 }

[cery999]

@jrk @ibtaylor