simple-wc.c

#include <stdio.h>
#include <fcntl.h>
#include <err.h>
#include <unistd.h>
#include <inttypes.h>

#define BUF_SIZE (1048576 * 10)

int main(int argc, char *argv[])
{
  static char char_buf[BUF_SIZE];
  static ssize_t buf_size = BUF_SIZE;
  void *buf = char_buf;
  char *p;
  ssize_t len;
  uint64_t linect;

  int fd = open("ten.json", O_RDONLY);
  if (fd < 0) {
    warn("bad open");
    return 1;
  }

  /*
  while((len = read(fd, buf, buf_size))) {
    for(p=buf;len--;p++){
      if(*p == '\n'){
        linect++;
      }
    }
  }
  */
  // faster!
  while((len = read(fd, buf, buf_size))) {
    for(p=buf;len>0;p+=2){
      if(*p == '\n'){
        counta++;
      }
      if(*(p+1) == '\n'){
        countb++;
      }
      len -=2;
    }
  }


  printf("%" PRIu64 "\n", linect);
}

Not sure how this compiles and does anything. Line 37 and line 40 reference undeclared variables counta and countb, neither of which are listed as computing linect.