From 7bd9bb82eed3064c241aa4d20212aadb769130cc Mon Sep 17 00:00:00 2001
From: Kaz Kylheku <kaz@kylheku.com>
Date: Wed, 7 May 2025 07:52:56 -0700
Subject: buf: int-buf: unsigned multiplication overflow.

* buf.c (int_buf): Do not multiply the buffer length by
8 as a built-in unsigned integer. Use the mul
function instead on the original Lisp integer length.
sign-extend handles bignum values for the bit width.
---
 buf.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/buf.c b/buf.c
index f5f27b39..906a800a 100644
--- a/buf.c
+++ b/buf.c
@@ -1305,12 +1305,11 @@ static val int_buf(val buf)
   val self = lit("int-buf");
   struct buf *b = buf_handle(buf, self);
   ucnum size = c_unum(b->len, self);
-  ucnum bits = size * 8;
   val ubn = make_bignum();
   mp_err mpe = mp_read_unsigned_bin(mp(ubn), b->data, size);
   if (mpe != MP_OKAY)
     do_mp_error(self, mpe);
-  return sign_extend(normalize(ubn), unum(bits));
+  return sign_extend(normalize(ubn), mul(b->len, num_fast(8)));
 }
 
 static val uint_buf(val buf)
-- 
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