sh: Apply set -u to variables in arithmetic.

Note that this only applies to variables that are actually used.
Things like (0 && unsetvar) do not cause an error.

Exp-run done by: pav (with some other sh(1) changes)

1 files changed, 2 insertions, 0 deletions

diff --git a/bin/sh/arith_yacc.c b/bin/sh/arith_yacc.c
index edb321f..63f236c 100644
--- a/bin/sh/arith_yacc.c
+++ b/bin/sh/arith_yacc.c
@@ -97,6 +97,8 @@ static arith_t arith_lookupvarint(char *varname)
 	arith_t result;
 
 	str = lookupvar(varname);
+	if (uflag && str == NULL)
+		yyerror("variable not set");
 	if (str == NULL || *str == '\0')
 		str = "0";
 	errno = 0;