/usr/ucb/learn has null pointer problems

[Arnold D. Robbins {EUCC}]

Subject: learn has null pointer bugs
Index:	/usr/src/usr.bin/learn/copy.c 4.3BSD

Description:
	On a machine that doesn't allow dereferencing null pointers
	(say, a Sun 4), learn will die fairly early into the sequence of
	lessons in "learn vi."
Repeat-By:
	Install learn on a Sun 4.

	In deference to the UCB folks, I don't know if the Tahoe version
	still has this problem or not.
Fix:
	Apply the following context diff to the file copy.c in the learn
	source directory.

*** copy.c.orig	Thu May 15 20:59:10 1986
--- copy.c	Mon Jul 17 17:30:59 1989
***************
*** 49,55 ****
  			}
  		r = wordb(s, t);	/* t = first token, r = rest */
  		p = action(t);		/* p = token class */
! 		if (*p == ONCE) {	/* some actions done only once per script */
  			if (wrong && !review) {	/* we are on 2nd time */
  				scopy(fin, NULL);
  				continue;
--- 49,55 ----
  			}
  		r = wordb(s, t);	/* t = first token, r = rest */
  		p = action(t);		/* p = token class */
! 		if (p && *p == ONCE) {	/* some actions done only once per script */
  			if (wrong && !review) {	/* we are on 2nd time */
  				scopy(fin, NULL);
  				continue;
***************
*** 265,271 ****
  				if (c == '\n')
  					break;
  				if (c == EOF)   {
! 					fflush(fo);
  					return;
  				}
  				if (fo != NULL)
--- 265,272 ----
  				if (c == '\n')
  					break;
  				if (c == EOF)   {
! 					if (fo != NULL)
! 						fflush(fo);
  					return;
  				}
  				if (fo != NULL)
***************
*** 281,287 ****
  	}
  	if (c == '#')
  		ungetc(c, fi);
! 	fflush(fo);
  }
  
  cmp(r)	/* compare two files for status; #cmp f1 f2 [ firstnlinesonly ] */
--- 282,289 ----
  	}
  	if (c == '#')
  		ungetc(c, fi);
! 	if (fo != NULL)
! 		fflush(fo);
  }
  
  cmp(r)	/* compare two files for status; #cmp f1 f2 [ firstnlinesonly ] */
-- 
Arnold Robbins -- Emory University Computing Center | Unix is a Registered
DOMAIN: arnold at unix.cc.emory.edu		    | Bell of AT&T Trademark
UUCP: gatech!emoryu1!arnold  PHONE: +1 404 727-7636 | Laboratories.
BITNET: arnold at emoryu1	     FAX:   +1 404 727-2599 |         -- Donn Seeley