bug in compiling dhcpcd-1.3.17pl5 (surprisingly fixed with a printf!)

[Olivier Baudron]

Can someone try the following experiment (needs a modem-cable).

1. Download http://www.phystech.com/download/dhcpcd-1.3.17-pl5.tar.gz
2. untar it, cd in the directory and "make"
3. Execute dhcpcd

On my computer, dhcpcd does not work! (the checksum in the server response
fails)

Now, insert a printf("coucou\n") in the file udpipgen.c between lines 42 and 43.
The procedure in_cksum should look like:

unsigned short in_cksum(addr,len)
unsigned short *addr;
int len;
{
  register int sum = 0;
  u_short answer = 0;
  register u_short *w = addr;
  register int nleft = len;
  while ( nleft > 1 )
    {
      sum += *w++;
      nleft -= 2;
    }
  printf ("coucou\n");
  if ( nleft == 1 )
    {
      *(u_char *)(&answer) = *(u_char *)w ;
      sum += answer;
    }
  sum = (sum >> 16) + (sum & 0xffff);
  sum += (sum >> 16);
  answer = ~sum;
  return answer;
}

Now, re-compile the file and re-build the executable dhcpcd.
On my computer, dhcpcd works!!!!

I also noticed, that when the option -O2 is removed, all works fine.

I tried these experiments many times, and the results were confirmed each time.
I also isolated the procedure in_cksum in a separate file. When compiling this
specific file with no optimization or with the inserted line printf("...")
dhcpcd works, but when compiling with -O2 and with no inserted line printf
("...") dhcpcd fails. Therefore the bug in compilation really concerns the above
lines of code.

My system is:
  Intel P133
  Linux 2.2.3
  egcs 1.1.2
  binutils 2.9.1.0.15
  libc6 2.0.7

Cheers,
Olivier.