Cでまともなエラーメッセージを出すマクロ (based on http://doi-t.hatenablog.com/entry/2013/12/10/094837)

error.h

#pragma once

#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <string.h>

#define PANIC(fmt, ...)                                                     \
  {                                                                         \
    err_msg(__FILE__, __FUNCTION__, __LINE__, "panic", fmt, ##__VA_ARGS__); \
    exit(EXIT_FAILURE);                                                     \
  }
#define ERROR(fmt, ...) \
  err_msg(__FILE__, __FUNCTION__, __LINE__, "error", fmt, ##__VA_ARGS__)
#define WARNING(fmt, ...) \
  err_msg(__FILE__, __FUNCTION__, __LINE__, "warning", fmt, ##__VA_ARGS__)

#define RED "\033[0;31m"
#define BOLD "\033[1m"
#define RESET_COLOR "\033[0m"

void err_msg(const char *file, const char *function, int line, const char *type,
             const char *fmt, ...) {
  // print error message
  fprintf(stderr, RED);
  fprintf(stderr, "%s: ", type);
  va_list va;
  va_start(va, fmt);
  vfprintf(stderr, fmt, va);
  va_end(va);
  fprintf(stderr, RESET_COLOR);
  fputc('\n', stderr);

  // print error source
  fprintf(stderr, BOLD);
  fprintf(stderr, " --> `%s` (%s:%d)", function, file, line);
  fprintf(stderr, RESET_COLOR);
  fputc('\n', stderr);

  // print errno
  if (errno != 0) {
    fprintf(stderr, " = errno: %s(%d)", strerror(errno),
            errno);       // print errno
    fputc('\n', stderr);  // new line
    errno = 0;
  }
}

main.c

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

#include "error.h"

int print_file_header(char *path) {
  int fd = open(path, O_RDONLY, 0644);
  if (fd == -1) {
    ERROR("fail to open file");
    return -1;
  }
  char buf[10];
  if (read(fd, buf, 10) == -1) {
    ERROR("fail to read file");
    return -1;
  }
  printf("%s\n", buf);
  return 0;
}

int main() {
  if (print_file_header("nonexistent_file.txt") == -1) {
    PANIC("failt to `print_file_header`");
  }
  return EXIT_SUCCESS;
}

Output

$ clang -Wall -Wextra -Werror -pedantic-errors -Wno-pragma-once-outside-header -Wno-gnu-zero-variadic-macro-arguments -std=gnu11 -g main.c -o main
$ ./main
error: fail to open file
 --> `print_file_header` (main.c:11)
 = errno: No such file or directory(2)
panic: failt to `print_file_header`
 --> `main` (main.c:25)