paramsubst bug

[Zefram <zefram@dcs.warwick.ac.uk>]

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% zsh <<< '
    set a b c d e
    echo "$@"
    set "$@"
    echo "$@"
  ' | cat -v
a b c d e
a HM-^B^N^HPM-^B^N^H M-x[^N^H@M-^B^N^Hks PM-^B^N^H0M-^B^N^HM-0M-^A^N^HM-x[^N^HM-x[^N^H@M-^B^N^Hks e

The bug is that the substitution of `"$@"' returns the original strings
from pparams, rather than duplicating them.  bin_set() frees pparams and
then duplicates its arguments -- but freeing pparams also freed some of
its arguments.  set has had this behaviour that tickles this bug since
3.0.1-test, but the subst.c code is far older and there are undoubtedly
other ways in which in can cause wrong behaviour.

I think the correct solution is for paramsubst() to always duplicate the
strings, rather than attempting this optimisation.  The patch below fixes
the array case, but there are very many code paths and I'm not sure if
any others might fail to duplicate.  (Look at the `copied' variable.)
We could do with some comments in subst.c to indicate which functions
can return their arguments unmodified.

This patch applies to both 3.1.2 and 3.0.3.

 -zefram

 *** Src/subst.c	1997/06/14 00:25:43	1.29
 --- Src/subst.c	1997/06/16 14:03:41
 ***************
 *** 1453,1462 ****
   		    return NULL;
   		if (qt && !*x && isarr != 2)
   		    y = dupstring(nulstring);
 ! 		else if (globsubst)
 ! 		    tokenize(y = dupstring(x));
 ! 		else
 ! 		    y = x;
   		insertlinknode(l, n, (void *) y), incnode(n);
   	    }
   
 --- 1453,1463 ----
   		    return NULL;
   		if (qt && !*x && isarr != 2)
   		    y = dupstring(nulstring);
 ! 		else {
 ! 		    y = dupstring(x);
 ! 		    if (globsubst)
 ! 			tokenize(y);
 ! 		}
   		insertlinknode(l, n, (void *) y), incnode(n);
   	    }
   

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