I dont know segmentation fault bug. I need to see how you translate it. But i can help you output bugs. You can show ncnn output data with pretty_print function or you should pay attention ncnn2opencv data type convertion. If you are using wrong convert algorithm you will get UINT8 data.
you can use float data conversation algorithm. You should use this function ncnn::Mat 1 channel -> cv::Mat CV_32FC1

#include <stdio.h>
#include <stdlib.h>

#include "lib/image_lib.h"
#include "lib/model_lib.h"

int main()
{
  /*
Variables  
*/
  unsigned int i;
  unsigned int error;
  
  ncnn_net_t model_instance;
  ncnn_extractor_t ex;

  ncnn_mat_t image_in; 
  ncnn_mat_t out;
  unsigned int out_w;
  float* out_data;
  
  /*
Read Image
*/
  image_raw image;
  error=imagelib_load_raw("data/image.png", &image);
  if(error) 
  {
    return error;
  }
  
  image_in = modellib_convertimage(&image);
  imagelib_free_raw(&image);
  
  /*
Load NCNN model
*/

  model_instance = modellib_load("model/model_output");
  ex = ncnn_extractor_create(model_instance);

  /*
Run NCNN model
*/
  ncnn_extractor_input(ex, "input_layer_input", image_in);
  printf("%d\n",1);
  ncnn_extractor_extract(ex, "output_layer", &out);
printf("%d\n",1);
  out_w = ncnn_mat_get_w(out);
  out_data = (float*)ncnn_mat_get_data(out);

  for (i = 0; i < out_w; i++)
  {
    printf("%f \n",out_data[i]);
  }

  /*
Destroy residue
*/
  ncnn_mat_destroy(image_in);
  ncnn_mat_destroy(out);
  ncnn_extractor_destroy(ex);
  ncnn_net_destroy(model_instance);

  return 0;
}

some of libraries are only wrapping functions like

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "model_lib.h"

/*
ncnn_net_t modellib_load(char* model_path):
Load model from model_path, and return ncnn_net_t
*/

ncnn_net_t modellib_load(char* model_path)
{
  /*
Variables  
*/
  char* param_file;
  char* model_file;
  unsigned int N;
  
  ncnn_net_t model_instance;
  ncnn_option_t opt;
  
  /*
Model and Parameter File Paths
*/
  N=strlen(model_path)*sizeof(char);
  
  param_file=(char*)malloc(N+6+1);
  strcpy(param_file,model_path);
  strcat(param_file,".param");
  
  model_file=(char*)malloc(N+4+1);
  strcpy(model_file,model_path);
  strcat(model_file,".bin");
  
  /*
Load Model
*/
  model_instance = ncnn_net_create();

  opt = ncnn_option_create();
  ncnn_option_set_use_vulkan_compute(opt, 0);
  ncnn_net_set_option(model_instance, opt);

  ncnn_net_load_param(model_instance, param_file);
  ncnn_net_load_model(model_instance, model_file);
  
  /*
Destroy Residue
*/
  ncnn_option_destroy(opt);
  free(param_file);
  free(model_file);
  
  return model_instance;
}

/*
ncnn_mat_t modellib_convertimage(image_raw* image_in):
Convert image from image_raw to ncnn_mat_t
*/

ncnn_mat_t modellib_convertimage(image_raw* image_in)
{
  ncnn_mat_t image_out = ncnn_mat_from_pixels(image_in->image, NCNN_MAT_PIXEL_RGB, image_in->width, image_in->height, image_in->width*3);

  const float mean_vals[3] = {0.f, 0.f, 0.f};
  const float norm_vals[3] = {256.f, 256.f, 256.f};
  ncnn_mat_substract_mean_normalize(image_out, mean_vals, norm_vals);
  
  return image_out;
}

image read etc. working properly, because when I try it with master branch, it works. I am using lodepng to read image.

what is ncnn_mat_get_data function ? How to convert out data?

It is from squeezenet_c_api example
https://ncnn.docsforge.com/master/api/ncnn_mat_get_data/

Can you print out data with pretty_print function after ncnn_extractor_extract(ex, "output_layer", &out) line
?

I'm using c, not cpp, this function contains properties of an object

then I can suggest you to follow the ncnn wiki with c++.

Error solved for "segmentation fault": add tf.keras.layer.Permute(3,1,2) to convert input from NHWC to NCHW. This solves segmentation fault. Because onnx2ncnn is for conversion from pytorch which uses NCHW.

How do I do this correct conversion to Mat in python?