3 files changed, 52 insertions, 4 deletions

diff --git a/usr.bin/diff/diff.c b/usr.bin/diff/diff.c
index a4e86b7855a8..91928651b188 100644
--- a/usr.bin/diff/diff.c
+++ b/usr.bin/diff/diff.c
@@ -100,6 +100,7 @@ static struct option longopts[] = {
 };
 
 void usage(void) __dead2;
+void conflicting_format(void) __dead2;
 void push_excludes(char *);
 void push_ignore_pats(char *);
 void read_excludes_file(char *file);
@@ -120,7 +121,7 @@ main(int argc, char **argv)
 	prevoptind = 1;
 	newarg = 1;
 	diff_context = 3;
-	diff_format = 0;
+	diff_format = D_UNSET;
 	while ((ch = getopt_long(argc, argv, OPTIONS, longopts, NULL)) != -1) {
 		switch (ch) {
 		case '0': case '1': case '2': case '3': case '4':
@@ -141,6 +142,8 @@ main(int argc, char **argv)
 			break;
 		case 'C':
 		case 'c':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			cflag = 1;
 			diff_format = D_CONTEXT;
 			if (optarg != NULL) {
@@ -154,13 +157,19 @@ main(int argc, char **argv)
 			dflags |= D_MINIMAL;
 			break;
 		case 'D':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_IFDEF;
 			ifdefname = optarg;
 			break;
 		case 'e':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_EDIT;
 			break;
 		case 'f':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_REVERSE;
 			break;
 		case 'H':
@@ -193,10 +202,12 @@ main(int argc, char **argv)
 			Nflag = 1;
 			break;
 		case 'n':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_NREVERSE;
 			break;
 		case 'p':
-			if (diff_format == 0)
+			if (diff_format == D_UNSET)
 				diff_format = D_CONTEXT;
 			dflags |= D_PROTOTYPE;
 			break;
@@ -207,6 +218,8 @@ main(int argc, char **argv)
 			rflag = 1;
 			break;
 		case 'q':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_BRIEF;
 			break;
 		case 'S':
@@ -223,6 +236,8 @@ main(int argc, char **argv)
 			break;
 		case 'U':
 		case 'u':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_UNIFIED;
 			if (optarg != NULL) {
 				l = strtol(optarg, &ep, 10);
@@ -249,9 +264,13 @@ main(int argc, char **argv)
 			push_excludes(optarg);
 			break;
 		case 'y':
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_SIDEBYSIDE;
 			break;
 		case OPT_CHANGED_GROUP_FORMAT:
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_GFORMAT;
 			group_format = optarg;
 			break;
@@ -264,6 +283,8 @@ main(int argc, char **argv)
 			ignore_file_case = 0;
 			break;
 		case OPT_NORMAL:
+			if (diff_format != D_UNSET)
+				conflicting_format();
 			diff_format = D_NORMAL;
 			break;
 		case OPT_TSIZE:
@@ -287,6 +308,8 @@ main(int argc, char **argv)
 		newarg = optind != prevoptind;
 		prevoptind = optind;
 	}
+	if (diff_format == D_UNSET)
+		diff_format = D_NORMAL;
 	argc -= optind;
 	argv += optind;
 
@@ -491,3 +514,11 @@ usage(void)
 
 	exit(2);
 }
+
+void
+conflicting_format(void)
+{
+
+	fprintf(stderr, "error: conflicting output format options.\n");
+	usage();
+}
diff --git a/usr.bin/diff/diff.h b/usr.bin/diff/diff.h
index 6a2c4cbea721..30387610fc19 100644
--- a/usr.bin/diff/diff.h
+++ b/usr.bin/diff/diff.h
@@ -50,6 +50,9 @@
 #define	D_GFORMAT	7	/* Diff with defined changed group format */
 #define D_SIDEBYSIDE    8	/* Side by side */
 
+#define	D_UNSET		-2
+
+
 /*
  * Output flags
  */
diff --git a/usr.bin/diff/tests/diff_test.sh b/usr.bin/diff/tests/diff_test.sh
index b605c4733f09..8385a6224865 100755
--- a/usr.bin/diff/tests/diff_test.sh
+++ b/usr.bin/diff/tests/diff_test.sh
@@ -11,6 +11,7 @@ atf_test_case brief_format
 atf_test_case b230049
 atf_test_case Bflag
 atf_test_case tabsize
+atf_test_case conflicting_format
 
 simple_body()
 {
@@ -49,8 +50,6 @@ unified_body()
 {
 	atf_check -o file:$(atf_get_srcdir)/unified_p.out -s eq:1 \
 		diff -up -L input_c1.in -L input_c2.in  "$(atf_get_srcdir)/input_c1.in" "$(atf_get_srcdir)/input_c2.in"
-	atf_check -o file:$(atf_get_srcdir)/unified_c9999.out -s eq:1 \
-		diff -u -c9999 -L input_c1.in -L input_c2.in "$(atf_get_srcdir)/input_c1.in" "$(atf_get_srcdir)/input_c2.in"
 	atf_check -o file:$(atf_get_srcdir)/unified_9999.out -s eq:1 \
 		diff -u9999 -L input_c1.in -L input_c2.in "$(atf_get_srcdir)/input_c1.in" "$(atf_get_srcdir)/input_c2.in"
 }
@@ -175,6 +174,20 @@ tabsize_body()
 	    diff -t --tabsize 1 A B
 }
 
+conflicting_format_body()
+{
+	printf "\tA\n" > A
+	printf "\tB\n" > B
+
+	atf_check -s exit:2 -e ignore diff -c -u A B
+	atf_check -s exit:2 -e ignore diff -e -f A B
+	atf_check -s exit:2 -e ignore diff -y -q A B
+	atf_check -s exit:2 -e ignore diff -q -u A B
+	atf_check -s exit:2 -e ignore diff -q -c A B
+	atf_check -s exit:2 -e ignore diff --normal -c A B
+	atf_check -s exit:2 -e ignore diff -c --normal A B
+}
+
 atf_init_test_cases()
 {
 	atf_add_test_case simple
@@ -188,4 +201,5 @@ atf_init_test_cases()
 	atf_add_test_case b230049
 	atf_add_test_case Bflag
 	atf_add_test_case tabsize
+	atf_add_test_case conflicting_format 
 }