From 791fe7ac57a9b660554219a99d63e07abfaa0982 Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Sun, 20 Dec 2020 20:01:20 -0800
Subject: [PATCH] [lld-macho] Fix memcpy ub after D93267

---
 lld/MachO/UnwindInfoSection.cpp | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lld/MachO/UnwindInfoSection.cpp b/lld/MachO/UnwindInfoSection.cpp
index acb4a9d..b4c3a31 100644
--- a/lld/MachO/UnwindInfoSection.cpp
+++ b/lld/MachO/UnwindInfoSection.cpp
@@ -318,8 +318,9 @@ void UnwindInfoSection::writeTo(uint8_t *buf) const {
         *ep++ = (it->second << COMPRESSED_ENTRY_FUNC_OFFSET_BITS) |
                 (cuep->functionAddress - functionAddressBase);
       }
-      memcpy(ep, page.localEncodings.data(),
-             page.localEncodings.size() * sizeof(uint32_t));
+      if (page.localEncodings.size() != 0)
+        memcpy(ep, page.localEncodings.data(),
+               page.localEncodings.size() * sizeof(uint32_t));
     } else {
       auto *p2p =
           reinterpret_cast<unwind_info_regular_second_level_page_header *>(pp);
-- 
2.7.4