sh: make smark a static variable instead of a local in main()

We are modifying it after setjmp and then accessing it after the jump,
so it cannot be a local.

MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D40415

1 files changed, 7 insertions, 1 deletions

diff --git a/bin/sh/main.c b/bin/sh/main.c
index a77f9528064d..3dd2b0d83738 100644
--- a/bin/sh/main.c
+++ b/bin/sh/main.c
@@ -100,7 +100,13 @@ static char *find_dot_file(char *);
 int
 main(int argc, char *argv[])
 {
-	struct stackmark smark = {0}, smark2;
+	/*
+	 * As smark is accessed after a longjmp, it cannot be a local in main().
+	 * The C standard specifies that the values of non-volatile local
+	 * variables are unspecified after a jump if modified between the
+	 * setjmp and longjmp.
+	 */
+	static struct stackmark smark, smark2;
 	volatile int state;
 	char *shinit;