From e4c7d8b38040518d42599eef8ddb5e67aa967a9c Mon Sep 17 00:00:00 2001
From: Mike Pall <mike>
Date: Mon, 30 Mar 2026 20:41:59 +0200
Subject: FFI: Shrink container of packed bitfield.

Reported by Huang Haiyang. #1451
---
 src/lj_cparse.c | 2 ++
 1 file changed, 2 insertions(+)

(limited to 'src/lj_cparse.c')

diff --git a/src/lj_cparse.c b/src/lj_cparse.c
index 45b05b36..f5c93d2e 100644
--- a/src/lj_cparse.c
+++ b/src/lj_cparse.c
@@ -1307,6 +1307,8 @@ static void cp_struct_layout(CPState *cp, CTypeID sid, CTInfo sattr)
 	  ct->info = CTINFO(CT_FIELD, ctype_cid(ct->info));
 	  ct->size = (bofs >> 3);  /* Store field offset. */
 	} else {
+	  if (csz > amask+1 && bsz <= amask+1)
+	    csz = amask+1;  /* Shrink container of packed bitfield. */
 	  ct->info = CTINFO(CT_BITFIELD,
 	    (info & (CTF_QUAL|CTF_UNSIGNED|CTF_BOOL)) +
 	    (csz << (CTSHIFT_BITCSZ-3)) + (bsz << CTSHIFT_BITBSZ));
-- 
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