From deab9a5e7917f9fecbf36cf97ca9cac7910df990 Mon Sep 17 00:00:00 2001
From: WormHeamer
Date: Sat, 9 Aug 2025 05:58:28 -0400
Subject: add N_DEAD node type, and assert to help prevent use-after-free

---
 ir.c | 28 +++++++++++-----------------
 1 file changed, 11 insertions(+), 17 deletions(-)

(limited to 'ir.c')

diff --git a/ir.c b/ir.c
index c935a67..42691ee 100644
--- a/ir.c
+++ b/ir.c
@@ -99,29 +99,18 @@ int type_check(Node *n) {
 /* nodes */
 
 const char *node_type_name(NodeType t) {
-	const char *names[] = {
-		"N/A",
-		"start", "if-else", "region", "phi", "stop",
-		"projection",
-		"return",
-		"keepalive",
-		"literal",
-		"add", "sub", "mul", "div",
-		"and", "or", "xor",
-		"lshift", "rshift",
-		"neg", "not",
-		"equal",
-		"not-equal",
-		"less",
-		"greater",
-		"less-or-equal",
-		"greater-or-equal",
+	static const char *names[] = {
+#define X(n, s) s,
+		NODE_TYPE_LIST
+#undef X
 	};
 	return names[t];
 }
 
 void node_die(Node *n, Proc *p) {
 	assert(n->refs == 0);
+	assert(n->op != N_DEAD);
+	n->op = N_DEAD;
 	n->prev_free = p->free_list;
 	p->free_list = n;
 }
@@ -182,6 +171,8 @@ void node_set_in(Proc *p, Node *n, int idx, Node *to) {
 }
 
 void node_add(Proc *p, Node *src, Node *dest) {
+	if (src) assert(src->op != N_DEAD);
+	if (dest) assert(dest->op != N_DEAD);
 	node_add_in(p, dest, src);
 	if (!src) return;
 	node_add_out(p, src, dest);
@@ -194,9 +185,11 @@ void node_add(Proc *p, Node *src, Node *dest) {
 }
 
 void node_remove(Proc *p, Node *src, Node *dest) {
+	assert(dest->op != N_DEAD);
 	node_del_in(dest, src);
 	if (dest->refs < 1) node_die(dest, p);
 	if (src) {
+		assert(src->op != N_DEAD);
 		node_del_out(src, dest);
 		if (src->out.len < 1) node_kill(src, p);
 	}
@@ -208,6 +201,7 @@ Node *node_new_empty(Proc *p, NodeType t) {
 	Node *n;
 	if (p->free_list) {
 		n = p->free_list;
+		assert(n->op == N_DEAD);
 		p->free_list = n->prev_free;
 		memset(n, 0, sizeof(Node));
 	} else {
-- 
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