diff: fix incorrectly displaying files as duplicates

When diff hits certain access errors, function diffreg() shows the error
message, and then returns to the calling function, which calls
print_status() with the return value.

However, in these cases, the return value isn't changed from the initial
default value of D_SAME.

Normally, print_status() with a value of D_SAME does nothing, so this
works out ok, however, if the "-s" flag is set, a message is displayed
showing identicality:

case D_SAME:
                if (sflag)
                        printf("Files %s%s and %s%s are identical\n",                                                                                                       path1, entry, path2, entry);
                break;

This then produces such results as:

% diff  -s /COPYRIGHT /var/run/rpcbind.sock
diff: /var/run/rpcbind.sock: Operation not supported
Files /COPYRIGHT and /var/run/rpcbind.sock are identical

% diff  -s /COPYRIGHT /etc/master.passwd
diff: /etc/master.passwd: Permission denied
Files /COPYRIGHT and /etc/master.passwd are identical

Create a D_ERROR status which is returned in such cases, and
print_status() then deals with that status seperately from D_SAME

PR:		252614
MFC after:	1 week

(cherry picked from commit fefb3c46a80fdde6f307e73a2b5b5aed806df1ce)

3 files changed, 8 insertions, 0 deletions

diff --git a/usr.bin/diff/diff.c b/usr.bin/diff/diff.c
index 0e46b96f9667..1bad6226f49d 100644
--- a/usr.bin/diff/diff.c
+++ b/usr.bin/diff/diff.c
@@ -511,6 +511,8 @@ print_status(int val, char *path1, char *path2, const char *entry)
 		printf("File %s%s is not a regular file or directory and was skipped\n",
 		    path2, entry);
 		break;
+	case D_ERROR:
+		break;
 	}
 }
 
diff --git a/usr.bin/diff/diff.h b/usr.bin/diff/diff.h
index 30387610fc19..1974b5cc08d6 100644
--- a/usr.bin/diff/diff.h
+++ b/usr.bin/diff/diff.h
@@ -83,6 +83,7 @@
 #define	D_MISMATCH2	4	/* path1 was a file, path2 a dir */
 #define	D_SKIPPED1	5	/* path1 was a special file */
 #define	D_SKIPPED2	6	/* path2 was a special file */
+#define	D_ERROR		7	/* A file access error occurred */
 
 struct excludes {
 	char *pattern;
diff --git a/usr.bin/diff/diffreg.c b/usr.bin/diff/diffreg.c
index 7d2b20b43def..4e887ab27c7b 100644
--- a/usr.bin/diff/diffreg.c
+++ b/usr.bin/diff/diffreg.c
@@ -299,6 +299,7 @@ diffreg(char *file1, char *file2, int flags, int capsicum)
 			if ((f1 = opentemp(file1)) == NULL ||
 			    fstat(fileno(f1), &stb1) == -1) {
 				warn("%s", file1);
+				rval = D_ERROR;
 				status |= 2;
 				goto closem;
 			}
@@ -309,6 +310,7 @@ diffreg(char *file1, char *file2, int flags, int capsicum)
 	}
 	if (f1 == NULL) {
 		warn("%s", file1);
+		rval = D_ERROR;
 		status |= 2;
 		goto closem;
 	}
@@ -320,6 +322,7 @@ diffreg(char *file1, char *file2, int flags, int capsicum)
 			if ((f2 = opentemp(file2)) == NULL ||
 			    fstat(fileno(f2), &stb2) == -1) {
 				warn("%s", file2);
+				rval = D_ERROR;
 				status |= 2;
 				goto closem;
 			}
@@ -330,6 +333,7 @@ diffreg(char *file1, char *file2, int flags, int capsicum)
 	}
 	if (f2 == NULL) {
 		warn("%s", file2);
+		rval = D_ERROR;
 		status |= 2;
 		goto closem;
 	}
@@ -365,6 +369,7 @@ diffreg(char *file1, char *file2, int flags, int capsicum)
 		break;
 	default:
 		/* error */
+		rval = D_ERROR;
 		status |= 2;
 		goto closem;
 	}