commit c9a537a8b0eddcabaf7622264b1f594fddaff553
author alx32 <103613512+alx32@users.noreply.github.com> Thu Mar 21 14:53:09 2024 -0700
committer Copybara-Service <copybara-worker@google.com> Thu Mar 21 14:54:49 2024 -0700
tree c4d20963ef39e08e428bd53565da69806a870669
parent b7e7dde32e49a00a9e6bc489c859d58472f59b26

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

Fixing gcc warning regarding creating non-null-terminated string:
```
../../lld/MachO/ObjC.cpp:1226:10: warning: 'char* strncpy(char*, const char*, size_t)' output truncated before terminating nul copying as many bytes from a string as its length [-Wstringop-truncation]
 1226 |   strncpy(strData, str, len);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~
../../lld/MachO/ObjC.cpp: In member function 'void {anonymous}::ObjcCategoryMerger::emitAndLinkPointerList(lld::macho::Defined*, uint32_t, const {anonymous}::ObjcCategoryMerger::ClassExtensionInfo&, const {anonymous}::ObjcCategoryMerger::PointerListInfo&)':
../../lld/MachO/ObjC.cpp:1223:24: note: length computed here
 1223 |   uint32_t len = strlen(str);
      |                  ~~~~~~^~~~~
```
This is not actually a bug, as `newSectionData` returns a
zero-initialized memory region, so the null terminator will be there.

GitOrigin-RevId: e4a672ef85f76c3402b81640e1e83e5d3069d1b9

MachO/ObjC.cpp

diff --git a/MachO/ObjC.cpp b/MachO/ObjC.cpp
index 66959cf..5902b82 100644
--- a/MachO/ObjC.cpp
+++ b/MachO/ObjC.cpp
@@ -1221,9 +1221,11 @@
 
 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);
+  // Copy the string chars and null-terminator
+  memcpy(strData, str, bufSize);
   return StringRef(strData, len);
 }