Alias fix

[Peter William Stephenson <pws@xxxxxx>]

> I was getting ready to release this as beta12, but last minute
> testing showed that there is a massive memory leak when you do
> filename completion.  I hadn't had a chance to look at it yet,
> but I thought I would through it out for everyone to take a
> look at

The problem was this: with the new history code, spaces in the input
line are significant.  For that reason, I had removed an extra space
that was being added by alias expansion at the end of each alias text.
Unfortunately, this meant that aliases were being removed from the
stack too early, so if the alias referred to the command itself at the
end of the expanded text (sticking noglob or nocorrect in front of
something was the most common) it didn't know it was already expanding
an alias and tried to do it again repeatedly.

The problem wasn't trivial to solve while still keeping track of
spaces.  The solution I've adopted (which has the major advantage over
all the other things I thought about that it works) is to allow the
aliases to be popped, but keep them in case the character before which
the pop command was hiding is put back in the input queue, and at that
point to restore the aliases.  As the code is fairly scrupulous about
having the right lexical state for the job in hand, this fixes the
problem.  A slight sophistication was that this has to happen even if
lexstop is set (i.e. we have swallowed past the last token) to allow
it to work when reading from strings.

I'm not mad keen on this solution due to the extra code (see the last
hunk), but I don't see a better way.  The positive side means that the
use of the INP_SPACE hack to add an extra (bogus) space to the input
for lexical purposes is now restricted to three calls in zle_tricky.c,
each time with a specially allocated string, so I shall probably be
able to remove it, which should shorten the input code and remove
another potential source of errors.  I'll leave that for another
patch.

By the way, we don't need to do this with history expansion, since
there's no recursive expansion problem; also `alstat' should take care
of itself as we don't need to look at it until expanding the next
word, so I haven't saved and restored that.  I've also taken the
opportunity to alter the input stack code too; it looked like I made a
mess of making it expand.

I've just discovered another bug, not yet fixed:  aliases ending in
spaces leave the spaces in the history line.  I'll have a go at that
next.

*** Src/hist.c.inpal	Tue Nov 14 13:20:05 1995
--- Src/hist.c	Wed Nov 15 14:29:01 1995
***************
*** 451,474 ****
  void
  hungetc(int c)
  {
!     if (lexstop)
! 	return;
!     if (expanding) {
! 	cs--;
! 	ll--;
!     }
  #if 0
!     /* debugging only */
!     if (hptr == chline)
! 	zerr("hungetc attempted at buffer start", NULL, 0);
!     else {
  #endif
- 	hptr--;
- 	if (*hptr == (char)bangchar && unset(NOBANGHIST))
  	    hptr--;
  #if 0
!     }
  #endif
      inungetc(c);
  }
  
--- 451,474 ----
  void
  hungetc(int c)
  {
!     if (!lexstop) {
! 	if (expanding) {
! 	    cs--;
! 	    ll--;
! 	}
  #if 0
! 	/* debugging only */
! 	if (hptr == chline)
! 	    zerr("hungetc attempted at buffer start", NULL, 0);
! 	else {
  #endif
  	    hptr--;
+ 	    if (*hptr == (char)bangchar && unset(NOBANGHIST))
+ 		hptr--;
  #if 0
! 	}
  #endif
+     }
      inungetc(c);
  }
  
*** Src/input.c.inpal	Tue Nov  7 09:48:35 1995
--- Src/input.c	Wed Nov 15 15:48:29 1995
***************
*** 95,100 ****
--- 95,122 ----
  
  static int instacksz = INSTACK_INITIAL;
  
+ /*
+  * Stack to deal with popped aliases.
+  * The problem is that we reach the end of the alias text and pop
+  * the alias at the point where we read the next character
+  * afterwards, which is probably whitespace, *then* go back and
+  * look to see if the expanded text needs re-expanding.  This
+  * means we need to keep track of the aliases we've popped and
+  * maybe add them back in if we unget the whitespace character.
+  *
+  * What happens is that ingetc(), when it pops an alias, sticks it on the
+  * stack, and inungetc() looks at that to see if it has to restore the
+  * alias(es); if so, the commands to pop an alias go back in the input
+  * queue. If ingetc() is called again, it sets the stack to zero.
+  * 
+  * We also need to be careful about `lexstop' when reading from a string.
+  * 
+  * Historical note:  the code used to add a bogus space to the end of
+  * aliases, after which the alias would be popped.  With the new
+  * history code, which keeps track of spaces correctly, this won't work.
+  */
+ static Alias *inalstack, *inalstacktop;
+ static int inalstacksz = INSTACK_INITIAL;
  
  /* Get the next character from the input.
   * Will call inputline() to get a new line where necessary.
***************
*** 104,109 ****
--- 126,132 ----
  int
  ingetc(void)
  {
+     inalstacktop = inalstack;
      for (;;) {
  	if (inbufleft) {
  	    inbufleft--;
***************
*** 116,124 ****
  	 */
  	if (inbufflags & INP_SPACE)  {
  	    /*
! 	     * INP_SPACE is flag from alias mechanism that space
! 	     * should follow expanded alias.  It is also used
! 	     * as a hack by zle_tricky.c.
  	     */
  	    inbufct--;		/* counts as a character in rest of shell */
  	    inbufflags &= ~INP_SPACE; /* ready to back up if necessary... */
--- 139,145 ----
  	 */
  	if (inbufflags & INP_SPACE)  {
  	    /*
! 	     * INP_SPACE is used as a hack by zle_tricky.c.
  	     */
  	    inbufct--;		/* counts as a character in rest of shell */
  	    inbufflags &= ~INP_SPACE; /* ready to back up if necessary... */
***************
*** 144,149 ****
--- 165,171 ----
  		    alstat = ALSTAT_MORE;
  		else
  		    alstat = ALSTAT_JUNK;
+ 		inalpush(ix);
  	    }
  	}
  
***************
*** 318,355 ****
  void
  inungetc(int c)
  {
!     if (lexstop)
! 	return;
!     if ((inbufflags & (INP_SPACE|INP_OLDSPACE)) == INP_OLDSPACE) {
! 	/* Use the space hack.  This is necessary because sometimes we need
! 	 * to back up the bogus space at the end of the line.
! 	 * We don't need to check c since the combination of flags only occurs
! 	 * if the last character got was a bogus space.
! 	 */
! 	inbufct++;		/* don't increment inbufleft, not in inbuf */
! 	inbufflags |= INP_SPACE;
! 	inbufflags &= ~INP_OLDSPACE; /* not necessary but cleaner */
! 	return;
!     }
!     if (inbufptr != inbuf) {
  #if 0
! 	/* Just for debugging: enable only if foul play suspected. */
! 	if (inbufptr[-1] != c)
! 	    fprintf(stderr, "Warning: backing up wrong character.\n");
  #endif
! 	/* Just decrement the pointer:  if it's not the same
! 	 * character being pushed back, we're in trouble anyway.
! 	 */
! 	inbufptr--;
! 	inbufct++;
! 	inbufleft++;
!     }
  #if 0
!     else {
! 	/* Just for debugging */
! 	fprintf(stderr, "Attempt to inungetc() at start of input.\n");
!     }
  #endif
  }
  
  /* stuff a whole file into the input queue and print it */
--- 340,377 ----
  void
  inungetc(int c)
  {
!     if (!lexstop) {
! 	if ((inbufflags & (INP_SPACE|INP_OLDSPACE)) == INP_OLDSPACE) {
! 	    /* Use the space hack.  This is necessary because sometimes we
! 	     * need to back up the bogus space at the end of the line.
! 	     * We don't need to check c since the combination of flags only
! 	     * occurs if the last character got was a bogus space.
! 	     */
! 	    inbufct++;		/* don't increment inbufleft, not in inbuf */
! 	    inbufflags |= INP_SPACE;
! 	    inbufflags &= ~INP_OLDSPACE; /* not necessary but cleaner */
! 	} else if (inbufptr != inbuf) {
  #if 0
! 	    /* Just for debugging: enable only if foul play suspected. */
! 	    if (inbufptr[-1] != c)
! 		fprintf(stderr, "Warning: backing up wrong character.\n");
  #endif
! 	    /* Just decrement the pointer:  if it's not the same
! 	     * character being pushed back, we're in trouble anyway.
! 	     */
! 	    inbufptr--;
! 	    inbufct++;
! 	    inbufleft++;
! 	}
  #if 0
!         else {
! 	    /* Just for debugging */
! 	    fprintf(stderr, "Attempt to inungetc() at start of input.\n");
! 	}
  #endif
+     }
+     if (inalstacktop > inalstack)
+ 	inalrestore();
  }
  
  /* stuff a whole file into the input queue and print it */
***************
*** 408,418 ****
  	/* Initial stack allocation */
  	instack = (struct instacks *)zalloc(instacksz*sizeof(struct instacks));
  	instacktop = instack;
!     } else if (instacktop > instack + instacksz) {
  	/* Expand the stack */
- 	instacksz += INSTACK_EXPAND;
  	instack = (struct instacks *)
! 	    realloc(instack, instacksz*sizeof(struct instacks));
      }
      instacktop->buf = inbuf;
      instacktop->bufptr = inbufptr;
--- 430,442 ----
  	/* Initial stack allocation */
  	instack = (struct instacks *)zalloc(instacksz*sizeof(struct instacks));
  	instacktop = instack;
!     } else if (instacktop == instack + instacksz) {
  	/* Expand the stack */
  	instack = (struct instacks *)
! 	    realloc(instack,
! 		    (instacksz + INSTACK_EXPAND)*sizeof(struct instacks));
! 	instacktop = instack + instacksz;
! 	instacksz += INSTACK_EXPAND;
      }
      instacktop->buf = inbuf;
      instacktop->bufptr = inbufptr;
***************
*** 458,461 ****
--- 482,513 ----
  
  	inpoptop();
      } while (remcont);
+ }
+ 
+ /**/
+ void
+ inalpush(Alias al)
+ {
+     if (!inalstack) {
+ 	 inalstack = (Alias *)zalloc(inalstacksz*sizeof(Alias));
+ 	 inalstacktop = inalstack;
+     } else if (inalstacktop - inalstack == inalstacksz) {
+ 	inalstack = (Alias *)
+ 	    realloc(inalstack, (inalstacksz + INSTACK_EXPAND)*sizeof(Alias));
+ 	inalstacktop = inalstack + inalstacksz;
+ 	inalstacksz += INSTACK_EXPAND;
+     }
+     *inalstacktop++ = al;
+ }
+ 
+ /**/
+ void
+ inalrestore(void)
+ {
+     while (inalstacktop > inalstack) {
+ 	Alias al = *--inalstacktop;
+ 	alstack[alstackind++] = al;
+ 	al->inuse = 1;
+ 	inpush("", INP_ALIAS);
+     }
  }

-- 
Peter Stephenson <pws@xxxxxx>       Tel: +49 33762 77366
WWW:  http://www.ifh.de/~pws/       Fax: +49 33762 77330
Deutches Electronen-Synchrotron --- Institut fuer Hochenergiephysik Zeuthen
DESY-IfH, 15735 Zeuthen, Germany.