[lld] [lld][macho] Fix gcc category merging warning (PR #86091)

[via llvm-commits]

https://github.com/alx32 updated https://github.com/llvm/llvm-project/pull/86091

>From 36f1e1a6a71ac7d2d27427a1ef6f6e628548ef7e Mon Sep 17 00:00:00 2001
From: alx32 <103613512+alx32 at users.noreply.github.com>
Date: Wed, 20 Mar 2024 23:17:01 -0700
Subject: [PATCH 1/2] [lld][macho] Fix gcc category merging warning

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

diff --git a/lld/MachO/ObjC.cpp b/lld/MachO/ObjC.cpp
index 40df2243b26f06..831a5bcea3acfe 100644
--- a/lld/MachO/ObjC.cpp
+++ b/lld/MachO/ObjC.cpp
@@ -1221,9 +1221,10 @@ void ObjcCategoryMerger::doCleanup() { generatedSectionData.clear(); }
 
 StringRef ObjcCategoryMerger::newStringData(const char *str) {
   uint32_t len = strlen(str);
-  auto &data = newSectionData(len + 1);
+  uint32_t bufSize = len + 1;
+  auto &data = newSectionData(bufSize);
   char *strData = reinterpret_cast<char *>(data.data());
-  strncpy(strData, str, len);
+  strncpy(strData, str, bufSize);
   return StringRef(strData, len);
 }
 

>From c13eeef4f70f372c2580800a232c0fb8016de7c4 Mon Sep 17 00:00:00 2001
From: alx32 <103613512+alx32 at users.noreply.github.com>
Date: Thu, 21 Mar 2024 08:49:09 -0700
Subject: [PATCH 2/2] Address Feedback #1

---
 lld/MachO/ObjC.cpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lld/MachO/ObjC.cpp b/lld/MachO/ObjC.cpp
index 831a5bcea3acfe..ded1e504d8ddf0 100644
--- a/lld/MachO/ObjC.cpp
+++ b/lld/MachO/ObjC.cpp
@@ -1224,7 +1224,8 @@ StringRef ObjcCategoryMerger::newStringData(const char *str) {
   uint32_t bufSize = len + 1;
   auto &data = newSectionData(bufSize);
   char *strData = reinterpret_cast<char *>(data.data());
-  strncpy(strData, str, bufSize);
+  // Copy the string chars and null-terminator
+  memcpy(strData, str, bufSize);
   return StringRef(strData, len);
 }