Don't forget to clear out the hold space for each subsequent file

when in -i mode so that each file gets a clean context of its own.

Add a regression test for the bug.

Tested with:	regression tests

3 files changed, 18 insertions, 4 deletions

diff --git a/usr.bin/sed/extern.h b/usr.bin/sed/extern.h
index cb4ae16..f2bd71b 100644
--- a/usr.bin/sed/extern.h
+++ b/usr.bin/sed/extern.h
@@ -52,5 +52,5 @@ char	*cu_fgets(char *, int, int *);
 int	 mf_fgets(SPACE *, enum e_spflag);
 int	 lastline(void);
 void	 process(void);
-void	 resetranges(void);
+void	 resetstate(void);
 char	*strregerror(int, regex_t *);
diff --git a/usr.bin/sed/main.c b/usr.bin/sed/main.c
index e4e426f..e17741f 100644
--- a/usr.bin/sed/main.c
+++ b/usr.bin/sed/main.c
@@ -390,7 +390,7 @@ mf_fgets(SPACE *sp, enum e_spflag spflag)
 			outfname = tmpfname;
 			if (!ispan) {
 				linenum = 0;
-				resetranges();
+				resetstate();
 			}
 		} else {
 			outfile = stdout;
diff --git a/usr.bin/sed/process.c b/usr.bin/sed/process.c
index c8b62c0..ca21ec7 100644
--- a/usr.bin/sed/process.c
+++ b/usr.bin/sed/process.c
@@ -234,6 +234,12 @@ redirect:
 					err(1, "%s", cp->t);
 				break;
 			case 'x':
+				/*
+				 * If the hold space is null, make it empty
+				 * but not null.  Otherwise the pattern space
+				 * will become null after the swap, which is
+				 * an abnormal condition.
+				 */
 				if (hs == NULL)
 					cspace(&HS, "", 0, REPLACE);
 				tspace = PS;
@@ -317,16 +323,24 @@ applies(struct s_command *cp)
 }
 
 /*
- * Reset all inrange markers.
+ * Reset the sed processor to its initial state.
  */
 void
-resetranges(void)
+resetstate(void)
 {
 	struct s_command *cp;
 
+	/*
+	 * Reset all inrange markers.
+	 */
 	for (cp = prog; cp; cp = cp->code == '{' ? cp->u.c : cp->next)
 		if (cp->a2)
 			cp->inrange = 0;
+
+	/*
+	 * Clear out the hold space.
+	 */
+	cspace(&HS, "", 0, REPLACE);
 }
 
 /*