input.c: ungot spaces patch

[P.Stephenson@xxxxxxxxxxxxx]

Here's a fix to input.c which Zoltan discovered was necessary.  The
problem is with the hack that the input code can put a bogus space at
the end of the input, which saves pushing it onto the stack.
Sometimes when putting a space back via inungetc() you actually need a
real space, if it was there originally, because of side effects.  I
should have put this in input.c to begin with but didn't realise it
would have a noticeable effect.

If recompiling, only input.c is affected, so you could do 'make -t'
and 'rm input.o' to avoid the affect of patching zsh.h.

*** Src/input.c.os	Mon Jul  3 14:31:16 1995
--- Src/input.c	Mon Aug 21 14:57:05 1995
***************
*** 46,52 ****
   * is to continue onto what's already in the input queue), INP_ALIAS (used
   * as a mark to pop the alias stack), or INP_SPACE (a shorthand way of
   * telling the input code to return a single space after the input string
!  * is exhausted).
   * 
   * Note that the input string is itself used as the input buffer: it is not
   * copied, nor is it every written back to, so using a constant string
--- 46,54 ----
   * is to continue onto what's already in the input queue), INP_ALIAS (used
   * as a mark to pop the alias stack), or INP_SPACE (a shorthand way of
   * telling the input code to return a single space after the input string
!  * is exhausted).  The code INP_OLDSPACE is used internally and should not be
!  * set initially:  it indicates that the INP_SPACE was just read and can be
!  * reset by a call to inungetc().
   * 
   * Note that the input string is itself used as the input buffer: it is not
   * copied, nor is it every written back to, so using a constant string
***************
*** 119,125 ****
  	     * 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 */
  	    return lastc = ' ';
  	}
  	/* Otherwise, see if we can pop the alias stack at this point. */
--- 121,128 ----
  	     * 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... */
! 	    inbufflags |= INP_OLDSPACE;	/* ...O.K. to back up an INP_SPACE */
  	    return lastc = ' ';
  	}
  	/* Otherwise, see if we can pop the alias stack at this point. */
***************
*** 323,334 ****
  {
      if (lexstop)
  	return;
!     if (!inbufleft && c == ' ' && !(inbufflags & INP_SPACE)) {
  	/* Use the space hack.  This is necessary because sometimes we need
  	 * to back up the bogus space at the end of the line.
  	 */
  	inbufct++;		/* don't increment inbufleft, not in inbuf */
  	inbufflags |= INP_SPACE;
  	return;
      }
      if (inbufptr != inbuf) {
--- 326,340 ----
  {
      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) {
*** Src/zsh.h.os	Mon Jul  3 13:32:01 1995
--- Src/zsh.h	Mon Aug 21 14:30:16 1995
***************
*** 204,209 ****
--- 204,210 ----
  #define INP_ALIAS	2	/* alias or history mark at end of word */
  #define INP_CONT	4	/* continue onto previously stacked input */
  #define INP_SPACE	8	/* return space after expanded alias */
+ #define INP_OLDSPACE	16	/* internal flag:  INP_SPACE was swallowed */
  
  /* linked list abstract data type */
  

-- 
Peter Stephenson <P.Stephenson@xxxxxxxxxxxxx>  Tel: +44 1792 205678 extn. 4461
WWW:  http://python.swan.ac.uk/~pypeters/      Fax: +44 1792 295324
Department of Physics, University of Wales, Swansea,
Singleton Park, Swansea, SA2 8PP, U.K.