From 0f16867d53aa0cf68ebac5aae110f6e5c34b05aa Mon Sep 17 00:00:00 2001
From: "Eric S. Raymond" <esr@thyrsus.com>
Date: Thu, 3 Nov 1994 20:37:17 +0000
Subject: [PATCH] Label patching really works now, and we can prove it.

---
 cupl.h      |  4 ++++
 cupl.y      | 24 ++++++++++++++++++++----
 interpret.c | 40 +++++++++++++++++++++++++++++++---------
 3 files changed, 55 insertions(+), 13 deletions(-)

diff --git a/cupl.h b/cupl.h
index 87e2a2c..f889001 100644
--- a/cupl.h
+++ b/cupl.h
@@ -51,6 +51,10 @@ typedef struct edon
 
     /* back-pointer to the symbol list, set if the node is an identifier */
     struct lvar_t	*syminf;    
+
+#ifdef PARSEDEBUG
+    int number;		/* statement number, if this is a STATEMENT node */
+#endif /* PARSEDEBUG */
 }
 node;
 
diff --git a/cupl.y b/cupl.y
index 80dabe7..1ff74b6 100644
--- a/cupl.y
+++ b/cupl.y
@@ -25,6 +25,10 @@ author first.
 #include <setjmp.h>
 
 #define	NULLNODE	(node *)NULL
+
+#ifdef PARSEDEBUG
+static int statement_count;
+#endif /* PARSEDEBUG */
 %}
 
 %start program
@@ -84,10 +88,22 @@ author first.
 /* a program description consists of a sequence of statements */
 program :    prog			{interpret($1);}
 
-prog	:    command prog		{$$ = cons(STATEMENT, $1, $2);}
-	|    IDENTIFIER command prog	{$$ = cons(STATEMENT, 
-						cons(LABEL, $1, $2), $3);}
-	|    /* EMPTY */		{$$ = (node *)NULL;}
+prog	:    command prog
+		{
+		    $$ = cons(STATEMENT, $1, $2);
+#ifdef PARSEDEBUG
+		    $$->number = ++statement_count;
+#endif /* PARSEDEBUG */
+		}
+	|    IDENTIFIER command prog
+		{
+		    $$ = cons(STATEMENT, cons(LABEL, $1, $2), $3);
+#ifdef PARSEDEBUG
+		    $$->number = ++statement_count;
+#endif /* PARSEDEBUG */
+		}
+	|    /* EMPTY */
+		{$$ = (node *)NULL;}
 	;
 
 /* statement syntax */
diff --git a/interpret.c b/interpret.c
index f6cf6c2..577d863 100644
--- a/interpret.c
+++ b/interpret.c
@@ -63,9 +63,15 @@ static void prettyprint(node *tree, int indent)
 	(void) printf("IDENTIFIER: %s\n", tree->u.string);
     else if (tree->type == STRING)
 	(void) printf("STRING: '%s'\n", tree->u.string);
+    else if (tree->type == STATEMENT && indent > 0)
+	(void) printf("-> STATEMENT %d\n", tree->number);
     else
     {
-	(void) printf("%-20s", tokdump(tree->type));
+	if (tree->type == STATEMENT)
+	    (void) printf("STATEMENT %2d       ", tree->number);
+	else
+	    (void) printf("%-20s", tokdump(tree->type));
+
 	if (verbose >= DEBUG_ALLOCATE)
 	    (void) printf("                          (%x -> %x, %x)",
 			  tree,
@@ -248,16 +254,16 @@ static bool r_label_rewrite(node *tp)
 	if (left && left->type == IDENTIFIER && left->syminf->labelref)
 	{
 #ifdef ODEBUG
-	    (void) printf("patching label reference to %s\n", left->u.string);
+	    (void) printf("patching label left reference to %s\n", left->u.string);
 #endif /* ODEBUG */
-	    left = left->syminf->target;
+	    tp->u.n.left = left->syminf->target;
 	}
 	if (right && right->type == IDENTIFIER && right->syminf->labelref)
 	{
 #ifdef ODEBUG
-	    (void) printf("patching label reference to %s\n", right->u.string);
+	    (void) printf("patching label right reference to %s\n", right->u.string);
 #endif /* ODEBUG */
-	    right = right->syminf->target;
+	    tp->u.n.right = right->syminf->target;
 	}
     }
 
@@ -305,15 +311,31 @@ static void rewrite(node *tree)
 void interpret(node *tree)
 /* interpret a program parse tree */
 {
+    if (check_errors(tree))
+	return;
+    rewrite(tree);
+
 #ifdef PARSEDEBUG
+    /* statement conses are made in reverse order; deal with this */
+    {
+	node	*np;
+	int statement_count = 0;
+
+	for_cdr(np, tree)
+	{
+	    if (np->type == STATEMENT)
+		++statement_count;
+	}
+
+	for_cdr(np, tree)
+	    if (np->type == STATEMENT)
+		np->number = statement_count - np->number + 1;
+    }
+
     if (verbose >= DEBUG_PARSEDUMP)
 	prettyprint(tree, 0);
 #endif /* PARSEDEBUG */
 
-    if (check_errors(tree))
-	return;
-    rewrite(tree);
-
     execute(tree);
 }
 
-- 
2.43.0