qemu-nox throws errors in cat.c file in xv6 while running make qemu-nox

Issue

I'm trying to implement ps command in xv6 (adding system call), I have followed the process of making one and in the end while using the command "make qemu-nox" to finally test the system call i get the following errors

gcc -fno-pic -static -fno-builtin -fno-strict-aliasing -O2 -Wall -MD -ggdb -m32 -Werror -fno-omit-frame-pointer -fno-stack-protector -fno-pie -no-pie   -c -o cat.o cat.c
cat.c: In function ‘cps’:
cat.c:9:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘{’ token
    9 | {
      | ^
cat.c:23:1: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘{’ token
   23 | {
      | ^
In file included from cat.c:3:
user.h:26:5: error: old-style parameter declarations in prototyped function definition
   26 | int cps(void)
      |     ^~~
cat.c:40: error: expected ‘{’ at end of input
   40 | }
      | 
cat.c:40: error: control reaches end of non-void function [-Werror=return-type]
   40 | }
      | 
cc1: all warnings being treated as errors
make: *** [<builtin>: cat.o] Error 1

This is the cat.c file, everything seems fine but i don't understand why is it showing errors

#include "types.h"
#include "stat.h"
#include "user.h"

char buf[512];

void
cat(int fd)
{
  int n;

  while((n = read(fd, buf, sizeof(buf))) > 0) {
    if (write(1, buf, n) != n) {
            printf(1, "cat: write error\n");
            exit();
    }
  }
  if(n < 0){
    printf(1, "cat: read error\n");
    exit();
  }
}

int
main(int argc, char *argv[])
{
  int fd, i;

  if(argc <= 1){
    cat(0);
    exit();
  }

  for(i = 1; i < argc; i++){
    if((fd = open(argv[i], 0)) < 0){
      printf(1, "cat: cannot open %s\n", argv[i]);
      exit();
    }
    cat(fd);
    close(fd);
  }
  exit();
}

Solution

The compiler is claiming that you're in a function named "cps()" on line 9 of your file cat.c, which is obviously not what that function is named. It's also complaining about an issue in user.h itself. This is the clue that the problem is not directly in your cat.c file, but somewhere in the headers it is including (probably in user.h).

Answered By - Peter Maydell