[lld-macho] Fix address sanitizer for category merging

[alx32]

FIxing the address sanitizer issue reported in #91548 .
The problem comes from the assignment auto bodyData = newSectionData which defaults to SmallVector<uint8_t> data = newSectionData - which actually creates a copy of the data, placed on the stack.
By explicitly using ArrayRef instead, we make sure that the original copy is used.
We also change the assignment in ObjcCategoryMerger::newStringData from auto to SmallVector<uint8_t> & to make it explicit.

[llvmbot]

@llvm/pr-subscribers-lld

@llvm/pr-subscribers-lld-macho

Author: None (alx32)

Changes

FIxing the address sanitizer issue reported in #91548 .
The problem comes from the assignment auto bodyData = newSectionData which defaults to SmallVector<uint8_t> data = newSectionData - which actually creates a copy of the data, placed on the stack.
By explicitly using ArrayRef instead, we make sure that the original copy is used.
We also change the assignment in ObjcCategoryMerger::newStringData from auto to SmallVector<uint8_t> & to make it explicit.

---

Full diff: https://github.com/llvm/llvm-project/pull/91680.diff

1 Files Affected:

• (modified) lld/MachO/ObjC.cpp (+2-2)

diff --git a/lld/MachO/ObjC.cpp b/lld/MachO/ObjC.cpp
index 96ec646095be8..9d1612beae872 100644
--- a/lld/MachO/ObjC.cpp
+++ b/lld/MachO/ObjC.cpp
@@ -1148,7 +1148,7 @@ void ObjcCategoryMerger::generateCatListForNonErasedCategories(
       assert(nonErasedCatBody && "Failed to relocate non-deleted category");
 
       // Allocate data for the new __objc_catlist slot
-      auto bodyData = newSectionData(target->wordSize);
+      llvm::ArrayRef<uint8_t> bodyData = newSectionData(target->wordSize);
 
       // We mark the __objc_catlist slot as belonging to the same file as the
       // category
@@ -1279,7 +1279,7 @@ void ObjcCategoryMerger::doCleanup() { generatedSectionData.clear(); }
 StringRef ObjcCategoryMerger::newStringData(const char *str) {
   uint32_t len = strlen(str);
   uint32_t bufSize = len + 1;
-  auto &data = newSectionData(bufSize);
+  SmallVector<uint8_t> &data = newSectionData(bufSize);
   char *strData = reinterpret_cast<char *>(data.data());
   // Copy the string chars and null-terminator
   memcpy(strData, str, bufSize);

[ellishg]

I think using auto & would have also been ok. But since this is a constant, it is preferred to use ArrayRef<> over const SmallVector<> &.

[alx32]

I am not sure I understand, it is using ArrayRef<>, or what is the suggested change ?