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Subject: Re: If someone wants to try... 
In-reply-to: "Sven Wischnowsky"'s message of "Mon, 17 Jan 2000 13:50:03 +0100."
             <200001171250.NAA21712@beta.informatik.hu-berlin.de> 
Date: Wed, 19 Jan 2000 12:48:50 +0000
From: Peter Stephenson <pws@pwstephenson.fsnet.co.uk>
Message-Id: <E12AuUe-0006zi-00.2000-01-19-12-45-49@cmailg2.svr.pol.co.uk>

Sven Wischnowsky wrote:
> Note that I'm not sure if this should be used in the distribution
> before the next official beta.

Well, we can't (or, rather, won't) test it if it isn't in.  I've found
three problems, described and supposedly fixed below.

If all the basic things get fixed, I'm tempted to put the whole thing in to
the source and see what happens.  In particular, I'm not sad that
dupstruct() and all its relatives have vanished.  That was the main use for
having routines that either used the heap or permanent allocation.  If this
means we're now (nearly) in a position to use either explicitly, and hence
junk all the HEAPALLOC/PERMALLOC stuff, it would make me very happy.


Problems:

First `[ ... ]' dumps core.  Is this the right fix (the middle parse.c
hunk)?  It seems to work.  I've added a debugging test for other unhandled
codes, and a couple of tests to Test/07cond.ztst (strictly these were
waiting for tests for builtins to come along, but the more the merrier).

Second:

% [[ ( -z foo && -z foo ) || -z foo ]]
zsh: bad cond code

It looks like the offsets for skipping chunks of `&&' and `||' weren't
right.  The text.c bit did work (e.g. if you embed that test in a function
and look at it), so I've assumed it's the chunk in evalcond() that's
wrong.  The offsets now seem to be right, although it's possible I've been
unnecessarily conservative in using variables. I've added a test for this,
too.

Third, the point already noted by Tanaka Akira, but fixed by Sven in 9361,
which boils down to:
  unset NULLCMD
  print "$(<anyfile)"
  zsh: redirection with no command

Looking more closely, the problem occurs at the test in getoutput() which
should pick up anything that's a simple read redirection and treat it
specially.  This wasn't happening because there was no WC_END marker at the
end of the wordcode programme.  According to parse.c, WC_END only gets put
there if the programme is empty, so this is not surprising, hence Sven's
fix.

But the fact that there's no marker unsettles me from another point of
view, namely execlist() ploughs on until it something which isn't a
WC_LIST, and if there's no WC_END marker it can in principle find any old
rubbish --- it seems usually to be the strings needed by the programme.  So
I would think that adding a WC_END marker unconditionally is the right
thing (four bytes per programme isn't so much).  I'm willing to take higher
counsel --- which means, if Sven can explain what I've missed about the
code that makes sure it knows when it's at the end of the programme.  I've
added another redirection test to pick this up.  This would make 9361
unnecessary, although maybe it would still be desirable?

--- Src/cond.c.cond	Tue Jan 18 22:01:34 2000
+++ Src/cond.c	Wed Jan 19 11:18:08 2000
@@ -43,7 +43,8 @@
 {
     struct stat *st;
     char *left, *right = NULL;
-    wordcode code = *state->pc++;
+    Wordcode pcode = state->pc++;
+    wordcode code = *pcode;
     int ctype = WC_COND_TYPE(code);
 
     switch (ctype) {
@@ -57,7 +58,7 @@
 		fprintf(stderr, " %s", condstr[ctype]);
 	    return evalcond(state);
 	} else {
-	    state->pc += WC_COND_SKIP(code) - 1;
+	    state->pc = pcode + (WC_COND_SKIP(code) + 1);
 	    return 0;
 	}
     case COND_OR:
@@ -66,7 +67,7 @@
 		fprintf(stderr, " %s", condstr[ctype]);
 	    return evalcond(state);
 	} else {
-	    state->pc += WC_COND_SKIP(code) - 1;
+	    state->pc = pcode + (WC_COND_SKIP(code) + 1);
 	    return 1;
 	}
     case COND_MOD:
--- Src/parse.c.cond	Tue Jan 18 21:35:08 2000
+++ Src/parse.c	Tue Jan 18 21:43:42 2000
@@ -2217,6 +2217,14 @@
 	    }
 	}
 	break;
+    case N_COND:
+	eccond((Cond) n);
+	break;
+#ifdef DEBUG
+    default:
+	dputs("BUG: node type not handled in ecomp().");
+	break;
+#endif
     }
 }
 

-- 
Peter Stephenson <pws@pwstephenson.fsnet.co.uk>