commit 1c84a372266b08b8b0ced3f3621898b4e422db4f
author Adrian Prantl <aprantl@apple.com> Thu Sep 11 11:07:38 2025 -0700
committer Copybara-Service <copybara-worker@google.com> Thu Sep 11 11:10:49 2025 -0700
tree 8d44b4ec79f4c753d00332320e1bff47f5fd582d
parent ef2dce4f913e0981ac5c7881f94b1b544836456b

[lldb] Fix undefined behavior (#158119)

https://green.lab.llvm.org/job/llvm.org/view/LLDB/job/lldb-cmake-sanitized/2178/consoleText

```
[2025-09-11T13:10:53.352Z] /Users/ec2-user/jenkins/workspace/llvm.org/lldb-cmake-sanitized/llvm-project/lldb/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp:14138:35: runtime error: signed integer overflow: 2147483624 + 608 cannot be represented in type 'int32_t' (aka 'int')
[2025-09-11T13:10:53.352Z] SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /Users/ec2-user/jenkins/workspace/llvm.org/lldb-cmake-sanitized/llvm-project/lldb/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp:14138:35 in
```

GitOrigin-RevId: e0117a555d3c84a1c8e0101fc46fe3a34fa48ce5

source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp

diff --git a/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp b/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp
index 89da4d2..f5f077f 100644
--- a/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp
+++ b/source/Plugins/Instruction/ARM/EmulateInstructionARM.cpp
@@ -14135,7 +14135,13 @@
   uint8_t overflow;
 
   uint64_t unsigned_sum = x + y + carry_in;
-  int64_t signed_sum = (int32_t)x + (int32_t)y + (int32_t)carry_in;
+  int64_t signed_sum = 0;
+  int32_t signed_sum32;
+  if (llvm::AddOverflow((int32_t)x, (int32_t)y, signed_sum32))
+    signed_sum++;
+  signed_sum += signed_sum32;
+
+  signed_sum += (int32_t)carry_in;
 
   result = UnsignedBits(unsigned_sum, 31, 0);
   //    carry_out = (result == unsigned_sum ? 0 : 1);