altos/scheme: Use memory manager mark code to note recursive print

This flags any object being printed and checks before recursing to
avoid infinite loops.

Signed-off-by: Keith Packard <keithp@keithp.com>

5 files changed, 99 insertions, 20 deletions

diff --git a/src/scheme/ao_scheme.h b/src/scheme/ao_scheme.h
index 48d0149b..cc7f8f1d 100644
--- a/src/scheme/ao_scheme.h
+++ b/src/scheme/ao_scheme.h
@@ -555,6 +555,21 @@ ao_scheme_move_memory(const struct ao_scheme_type *type, void **ref);
 void *
 ao_scheme_alloc(int size);
 
+/* Marks an object as being printed, returns 1 if it was already marked */
+int
+ao_scheme_print_mark_addr(void *addr);
+
+int
+ao_scheme_print_mark_poly(ao_poly poly);
+
+/* Notes that printing has started */
+void
+ao_scheme_print_start(void);
+
+/* Notes that printing has ended */
+void
+ao_scheme_print_stop(void);
+
 #define AO_SCHEME_COLLECT_FULL		1
 #define AO_SCHEME_COLLECT_INCREMENTAL	0
 
diff --git a/src/scheme/ao_scheme_cons.c b/src/scheme/ao_scheme_cons.c
index 912100a9..0b3cbf80 100644
--- a/src/scheme/ao_scheme_cons.c
+++ b/src/scheme/ao_scheme_cons.c
@@ -181,16 +181,17 @@ ao_scheme_cons_write(ao_poly c)
 	ao_poly			cdr;
 	int			first = 1;
 
+	ao_scheme_print_start();
 	printf("(");
 	while (cons) {
 		if (!first)
 			printf(" ");
-		ao_scheme_poly_write(cons->car);
-		cdr = cons->cdr;
-		if (cdr == c) {
-			printf(" ...");
+		if (ao_scheme_print_mark_addr(cons)) {
+			printf("...");
 			break;
 		}
+		ao_scheme_poly_write(cons->car);
+		cdr = cons->cdr;
 		if (ao_scheme_poly_type(cdr) == AO_SCHEME_CONS) {
 			cons = ao_scheme_poly_cons(cdr);
 			first = 0;
@@ -201,6 +202,7 @@ ao_scheme_cons_write(ao_poly c)
 		}
 	}
 	printf(")");
+	ao_scheme_print_stop();
 }
 
 void
@@ -209,13 +211,15 @@ ao_scheme_cons_display(ao_poly c)
 	struct ao_scheme_cons	*cons = ao_scheme_poly_cons(c);
 	ao_poly			cdr;
 
+	ao_scheme_print_start();
 	while (cons) {
-		ao_scheme_poly_display(cons->car);
-		cdr = cons->cdr;
-		if (cdr == c) {
+		if (ao_scheme_print_mark_addr(cons)) {
 			printf("...");
 			break;
 		}
+		ao_scheme_poly_display(cons->car);
+
+		cdr = cons->cdr;
 		if (ao_scheme_poly_type(cdr) == AO_SCHEME_CONS)
 			cons = ao_scheme_poly_cons(cdr);
 		else {
@@ -223,6 +227,7 @@ ao_scheme_cons_display(ao_poly c)
 			cons = NULL;
 		}
 	}
+	ao_scheme_print_stop();
 }
 
 int
diff --git a/src/scheme/ao_scheme_frame.c b/src/scheme/ao_scheme_frame.c
index 7f521863..3f4c9157 100644
--- a/src/scheme/ao_scheme_frame.c
+++ b/src/scheme/ao_scheme_frame.c
@@ -41,7 +41,6 @@ frame_vals_mark(void *addr)
 			  ao_scheme_poly_atom(v->atom)->name,
 			  MDBG_OFFSET(ao_scheme_ref(v->atom)),
 			  MDBG_OFFSET(ao_scheme_ref(v->val)), f);
-		MDBG_DO(ao_scheme_poly_write(v->val));
 		MDBG_DO(printf("\n"));
 	}
 }
diff --git a/src/scheme/ao_scheme_mem.c b/src/scheme/ao_scheme_mem.c
index e7e89b89..c7d6b1f8 100644
--- a/src/scheme/ao_scheme_mem.c
+++ b/src/scheme/ao_scheme_mem.c
@@ -280,6 +280,10 @@ static const void ** const ao_scheme_cache[] = {
 
 #define AO_SCHEME_BUSY_SIZE	((AO_SCHEME_POOL + 31) / 32)
 
+static int	ao_scheme_printing, ao_scheme_print_cleared;
+#if DBG_MEM
+static int	ao_scheme_collecting;
+#endif
 static uint8_t	ao_scheme_busy[AO_SCHEME_BUSY_SIZE];
 static uint8_t	ao_scheme_cons_note[AO_SCHEME_BUSY_SIZE];
 static uint8_t	ao_scheme_cons_last[AO_SCHEME_BUSY_SIZE];
@@ -550,6 +554,7 @@ ao_scheme_collect(uint8_t style)
 	MDBG_MOVE("collect %d\n", ao_scheme_collects[style]);
 #endif
 	MDBG_DO(ao_scheme_frame_write(ao_scheme_frame_poly(ao_scheme_frame_global)));
+	MDBG_DO(++ao_scheme_collecting);
 
 	ao_scheme_reset_stack();
 
@@ -681,6 +686,7 @@ ao_scheme_collect(uint8_t style)
 #if DBG_MEM_STACK
 	fprintf(stderr, "max collect stack depth %lu\n", mem_collect_max_depth);
 #endif
+	MDBG_DO(--ao_scheme_collecting);
 	return AO_SCHEME_POOL - ao_scheme_top;
 }
 
@@ -1021,3 +1027,53 @@ ao_scheme_frame_fetch(int id)
 	save_frame[id] = NULL;
 	return frame;
 }
+
+int
+ao_scheme_print_mark_addr(void *addr)
+{
+	int	offset;
+
+#if DBG_MEM
+	if (ao_scheme_collecting)
+		ao_scheme_abort();
+#endif
+
+	if (!AO_SCHEME_IS_POOL(addr))
+		return 1;
+
+	if (!ao_scheme_print_cleared) {
+		ao_scheme_print_cleared = 1;
+		memset(ao_scheme_busy, '\0', sizeof (ao_scheme_busy));
+	}
+	offset = pool_offset(addr);
+	if (busy(ao_scheme_busy, offset))
+		return 1;
+	mark(ao_scheme_busy, offset);
+	return 0;
+}
+
+int
+ao_scheme_print_mark_poly(ao_poly p)
+{
+	uint8_t type = ao_scheme_poly_base_type(p);
+
+	if (type == AO_SCHEME_INT)
+		return 1;
+	return ao_scheme_print_mark_addr(ao_scheme_ref(p));
+}
+
+/* Notes that printing has started */
+void
+ao_scheme_print_start(void)
+{
+	ao_scheme_printing++;
+}
+
+/* Notes that printing has ended */
+void
+ao_scheme_print_stop(void)
+{
+	ao_scheme_printing--;
+	if (ao_scheme_printing == 0)
+		ao_scheme_print_cleared = 0;
+}
diff --git a/src/scheme/ao_scheme_vector.c b/src/scheme/ao_scheme_vector.c
index a4127f64..ff2067e2 100644
--- a/src/scheme/ao_scheme_vector.c
+++ b/src/scheme/ao_scheme_vector.c
@@ -78,16 +78,19 @@ ao_scheme_vector_write(ao_poly v)
 	struct ao_scheme_vector	*vector = ao_scheme_poly_vector(v);
 	unsigned int i;
 
-	printf("#(");
-	for (i = 0; i < vector->length; i++) {
-		if (i != 0)
-			printf(" ");
-		if (vector->vals[i] == v)
-			printf ("...");
-		else
+	ao_scheme_print_start();
+	if (ao_scheme_print_mark_addr(vector))
+		printf ("...");
+	else {
+		printf("#(");
+		for (i = 0; i < vector->length; i++) {
+			if (i != 0)
+				printf(" ");
 			ao_scheme_poly_write(vector->vals[i]);
+		}
+		printf(")");
 	}
-	printf(")");
+	ao_scheme_print_stop();
 }
 
 void
@@ -96,10 +99,11 @@ ao_scheme_vector_display(ao_poly v)
 	struct ao_scheme_vector *vector = ao_scheme_poly_vector(v);
 	unsigned int i;
 
-	for (i = 0; i < vector->length; i++) {
-		if (vector->vals[i] == v)
-			printf("...");
-		else
+	ao_scheme_print_start();
+	if (ao_scheme_print_mark_addr(vector))
+		printf ("...");
+	else {
+		for (i = 0; i < vector->length; i++)
 			ao_scheme_poly_display(vector->vals[i]);
 	}
 }