[PATCH] D148217: [BOLT][NFC] Fix UB due to unaligned load in DebugStrOffsetsWriter

[Job Noorman via Phabricator via llvm-commits]

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The following tests fail when enabling UBSan due to an unaligned memory
load:

> runtime error: load of misaligned address 0x620000000643 for type
> 'const uint32_t' (aka 'const unsigned int'), which requires 4 byte
> alignment



  BOLT :: AArch64/asm-func-debug.test
  BOLT :: AArch64/update-debug-reloc.test
  BOLT :: X86/asm-func-debug.test
  BOLT :: X86/dwarf5-df-dualcu.test
  BOLT :: X86/dwarf5-df-mono-dualcu.test
  BOLT :: X86/dwarf5-ftypes-dwp-input-dwo-output.test
  BOLT :: X86/dwarf5-locaddrx.test
  BOLT :: X86/dwarf5-split-dwarf4-monolithic.test
  BOLT :: X86/inlined-function-mixed.test
  BOLT :: non-empty-debug-line.test

This patch fixes this by using read32le for the load.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D148217

Files:
  bolt/lib/Core/DebugData.cpp


Index: bolt/lib/Core/DebugData.cpp
===================================================================
--- bolt/lib/Core/DebugData.cpp
+++ bolt/lib/Core/DebugData.cpp
@@ -1166,7 +1166,7 @@
          "Dwarf String Offsets Byte Size is not supported.");
   uint32_t Index = 0;
   for (uint64_t Offset = 0; Offset < Contr->Size; Offset += DwarfOffsetByteSize)
-    IndexToAddressMap[Index++] = *reinterpret_cast<const uint32_t *>(
+    IndexToAddressMap[Index++] = support::endian::read32le(
         StrOffsetsSection.Data.data() + Contr->Base + Offset);
 }
 


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