bin/169274: [patch] diff exit code always reports "trouble" when there are differences between 2 files

[Garrett Cooper]

>Number:         169274
>Category:       bin
>Synopsis:       [patch] diff exit code always reports "trouble" when there are differences between 2 files
>Confidential:   no
>Severity:       serious
>Priority:       high
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Jun 20 18:30:11 UTC 2012
>Closed-Date:
>Last-Modified:
>Originator:     Garrett Cooper
>Release:        9-STABLE
>Organization:
EMC Isilon
>Environment:
FreeBSD forza.west.isilon.com 9.0-STABLE FreeBSD 9.0-STABLE #0 r236977M: Tue Jun 12 17:38:29 PDT 2012     root at forza.west.isilon.com:/usr/obj/usr/src/sys/FORZA  amd64
>Description:
diff doesn't do the right thing according to the manpage differentiating errors from differences; from diff(1)...

RETURN VALUE
       diff returns 0 if the files are identical or 1 if the files differ.  If
       one or both of the files cannot be opened, then the return value is set
       to 2.

Example:

$ diff valid.output unittest.dip >/dev/null
$ echo $?
2
$

The patch attached fixes this logic error and another inconsistency with "magic numbers":

$ diff -q /usr/src/contrib/diff/src/diff.c  /usr/src/contrib/diff/src/diff.c ; echo $?
0
$ diff -q /usr/src/contrib/diff/src/diff.c  /usr/src/contrib/diff/src/diff.h ; echo $?
Files /usr/src/contrib/diff/src/diff.c and /usr/src/contrib/diff/src/diff.h differ
1
$ diff -q /usr/src/contrib/diff/src/diff.c  /usr/src/contrib/diff/src/diff.c~ ; echo $?
diff: /usr/src/contrib/diff/src/diff.c~: No such file or directory
2
$ diff -N /usr/src/contrib/diff/src/diff.c /usr/src/contrib/diff/src/diff.c~ >/dev/null; echo $?
1
>How-To-Repeat:
diff /usr/src/contrib/diff/src/diff.c  /usr/src/contrib/diff/src/diff.h >/dev/null
ec=$?
if [ $ec -eq 1 ]
then
    echo PASS
else
    echo FAIL
fi
>Fix:


Patch attached with submission follows:

Index: contrib/diff/src/analyze.c
===================================================================
--- contrib/diff/src/analyze.c	(revision 237106)
+++ contrib/diff/src/analyze.c	(working copy)
@@ -771,7 +771,7 @@
 }
 
 /* If CHANGES, briefly report that two files differed.
-   Return 2 if trouble, CHANGES otherwise.  */
+   Returns CHANGES.  */
 static int
 briefly_report (int changes, struct file_data const filevec[])
 {
@@ -780,8 +780,7 @@
       char const *label0 = file_label[0] ? file_label[0] : filevec[0].name;
       char const *label1 = file_label[1] ? file_label[1] : filevec[1].name;
       message ("Files %s and %s differ\n", label0, label1);
-      if (! brief)
-	changes = 2;
+      changes = 1;
     }
 
   return changes;
Index: contrib/diff/src/diff.c
===================================================================
--- contrib/diff/src/diff.c	(revision 237106)
+++ contrib/diff/src/diff.c	(working copy)
@@ -261,7 +261,7 @@
   char *numend;
 
   /* Do our initializations.  */
-  exit_failure = 2;
+  exit_failure = EXIT_TROUBLE;
   initialize_main (&argc, &argv);
   program_name = argv[0];
   setlocale (LC_ALL, "");


>Release-Note:
>Audit-Trail:
>Unformatted: