From 49a1beba86c5a5982634c4f5a2a010783bc23a80 Mon Sep 17 00:00:00 2001
From: kevans <kevans@FreeBSD.org>
Date: Wed, 27 Jun 2018 21:11:28 +0000
Subject: [PATCH] MFC r335404: sort(1): Fix -m when only implicit stdin is used
 for input

Observe:

printf "a\nb\nc\n" > /tmp/foo
# Next command results in no output
cat /tmp/foo | sort -m
# Next command results in proper output
cat /tmp/foo | sort -m -
# Also works:
sort -m /tmp/foo

Some const'ification was done to simplify the actual solution of adding "-"
explicitly to the file list if we didn't have any file arguments left over.

PR:		190099
---
 usr.bin/sort/file.c | 4 ++--
 usr.bin/sort/file.h | 4 ++--
 usr.bin/sort/sort.c | 6 +++++-
 3 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/usr.bin/sort/file.c b/usr.bin/sort/file.c
index 92aabefd087..1cdc774679c 100644
--- a/usr.bin/sort/file.c
+++ b/usr.bin/sort/file.c
@@ -227,7 +227,7 @@ file_list_init(struct file_list *fl, bool tmp)
  * Add a file name to the list
  */
 void
-file_list_add(struct file_list *fl, char *fn, bool allocate)
+file_list_add(struct file_list *fl, const char *fn, bool allocate)
 {
 
 	if (fl && fn) {
@@ -1116,7 +1116,7 @@ file_headers_merge(size_t fnum, struct file_header **fh, FILE *f_out)
  * stdout.
  */
 static void
-merge_files_array(size_t argc, char **argv, const char *fn_out)
+merge_files_array(size_t argc, const char **argv, const char *fn_out)
 {
 
 	if (argv && fn_out) {
diff --git a/usr.bin/sort/file.h b/usr.bin/sort/file.h
index f3a7d3abc02..724928a7c05 100644
--- a/usr.bin/sort/file.h
+++ b/usr.bin/sort/file.h
@@ -66,7 +66,7 @@ struct file_reader;
  */
 struct file_list
 {
-	char			**fns;
+	const char *		*fns;
 	size_t			 count;
 	size_t			 sz;
 	bool			 tmp;
@@ -108,7 +108,7 @@ char *new_tmp_file_name(void);
 void tmp_file_atexit(const char *tmp_file);
 
 void file_list_init(struct file_list *fl, bool tmp);
-void file_list_add(struct file_list *fl, char *fn, bool allocate);
+void file_list_add(struct file_list *fl, const char *fn, bool allocate);
 void file_list_populate(struct file_list *fl, int argc, char **argv, bool allocate);
 void file_list_clean(struct file_list *fl);
 
diff --git a/usr.bin/sort/sort.c b/usr.bin/sort/sort.c
index 5edc5af6703..bbe8af4607b 100644
--- a/usr.bin/sort/sort.c
+++ b/usr.bin/sort/sort.c
@@ -1299,7 +1299,11 @@ main(int argc, char **argv)
 		struct file_list fl;
 
 		file_list_init(&fl, false);
-		file_list_populate(&fl, argc, argv, true);
+		/* No file arguments remaining means "read from stdin." */
+		if (argc == 0)
+			file_list_add(&fl, "-", true);
+		else
+			file_list_populate(&fl, argc, argv, true);
 		merge_files(&fl, outfile);
 		file_list_clean(&fl);
 	}
-- 
2.45.0