Re: [patch] 5.2.1 (hostid): don't display sign-extended part

[Paul Eggert]

Thanks for reporting the bug.  That fix isn't quite right, since it attempts
to print a "long" with "lx"; this has undefined behavior.

Also, you put an "8" into the format without mentioning the issue of
print width.  I like the idea of fixed-width (that's what Solaris
does) but it should be zero-padded, not space padded.

I installed the following fix instead.

2005-06-16  Paul Eggert  <address@hidden>

        * src/hostid.c (main): Don't print fewer than 8 digits, or spurious
        leading "f"s.  "f" problem reported by Tim Waugh.
        * NEWS: Document this.

Index: NEWS
===================================================================
RCS file: /fetish/cu/NEWS,v
retrieving revision 1.296
diff -p -u -r1.296 NEWS
--- NEWS        15 Jun 2005 00:06:34 -0000      1.296
+++ NEWS        16 Jun 2005 23:44:37 -0000
@@ -131,6 +131,9 @@ GNU coreutils NEWS                      
 
 ** Improved portability
 
+  hostid now prints exactly 8 hexadecimal digits, possibly with leading zeros,
+  and without any spurious leading "fff..." on 64-bit hosts.
+
   nice now works on Darwin 7.7.0 in spite of its invalid definition of NZERO.
 
   `rm -r' can remove all entries in a directory even when it is on a
Index: src/hostid.c
===================================================================
RCS file: /fetish/cu/src/hostid.c,v
retrieving revision 1.31
diff -p -u -r1.31 hostid.c
--- src/hostid.c        14 May 2005 07:58:37 -0000      1.31
+++ src/hostid.c        16 Jun 2005 23:44:37 -0000
@@ -62,7 +62,7 @@ Print the numeric identifier (in hexadec
 int
 main (int argc, char **argv)
 {
-  long int id;
+  unsigned int id;
 
   initialize_main (&argc, &argv);
   program_name = argv[0];
@@ -84,7 +84,13 @@ main (int argc, char **argv)
     }
 
   id = gethostid ();
-  printf ("%lx\n", id);
+
+  /* POSIX says gethostid returns a "32-bit identifier" but is silent
+     whether it's sign-extended.  Turn off any sign-extension.  This
+     is a no-op unless unsigned int is wider than 32 bits.  */
+  id &= 0xffffffff;
+
+  printf ("%08x\n", id);
 
   exit (EXIT_SUCCESS);
 }