diff -up arc-5.21p/arclzw.c~ arc-5.21p/arclzw.c

--- arc-5.21p/arclzw.c~	2010-08-07 15:06:42.000000000 +0200

+++ arc-5.21p/arclzw.c	2020-02-15 10:34:25.469210421 +0100

@@ -57,9 +57,10 @@ static VOID     putcode();

 #define NOT_FND  0xFFFF

 extern u_char	*pinbuf;

+extern u_char	*outend; 

+extern u_char	*outbuf;

 u_char		*inbeg, *inend;

-u_char          *outbuf;

-u_char          *outbeg, *outend; 

+u_char          *outbeg;

 static int      sp;		/* current stack pointer */

 static int	inflag;

diff -up arc-5.21p/arcunp.c~ arc-5.21p/arcunp.c

--- arc-5.21p/arcunp.c~	2010-08-07 15:06:42.000000000 +0200

+++ arc-5.21p/arcunp.c	2020-02-15 10:33:15.751795541 +0100

@@ -33,14 +33,14 @@ VOID	arcdie(), codebuf();

 extern u_char   state;		/* repeat unpacking state */

 extern int	lastc;

+extern short    crcval;		/* CRC check value */

+extern long     stdlen;		/* bytes to read */

 /* repeat unpacking states */

 #define NOHIST 0		/* no relevant history */

 #define INREP 1			/* sending a repeated value */

-short    crcval;		/* CRC check value */

-long     stdlen;		/* bytes to read */

 #if	!DOS

 static int	gotcr;		/* got a carriage return? */

 #endif