From de7d1facf3609165bb8b8bb96e19022ef4f46dfc Mon Sep 17 00:00:00 2001
From: ISSOtm <eldredhabert0@gmail.com>
Date: Sat, 3 Apr 2021 18:31:19 +0200
Subject: [PATCH] Add assertion that an expansion's total len doesn't overflow

Typically not needed because the recursion depth limit should prevent it,
but it might help debug weird lexer issues.
---
 src/asm/lexer.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/asm/lexer.c b/src/asm/lexer.c
index 367210e1..e7684c12 100644
--- a/src/asm/lexer.c
+++ b/src/asm/lexer.c
@@ -761,7 +761,10 @@ static void beginExpansion(size_t distance, uint8_t skip, char const *str, bool
 	struct Expansion *parent = NULL;
 	unsigned int depth = 0;
 
-#define LOOKUP_PRE_NEST(exp) (exp)->totalLen += size - skip
+#define LOOKUP_PRE_NEST(exp) do { \
+	assert((exp)->totalLen <= SIZE_MAX - (size - skip)); \
+	(exp)->totalLen += size - skip; \
+} while (0)
 #define LOOKUP_POST_NEST(exp) do { \
 	if (name && ++depth >= nMaxRecursionDepth) \
 		fatalerror("Recursion limit (%zu) exceeded\n", nMaxRecursionDepth); \