[Lldb-commits] [lldb] 846909e - [lldb] Fix UBSan regression in GetSLEB128

[Jan Kratochvil via lldb-commits]

Author: Jan Kratochvil
Date: 2020-06-05T12:00:44+02:00
New Revision: 846909e2ab0bd279ae2a8ec86074521f59c49eb3

URL: https://github.com/llvm/llvm-project/commit/846909e2ab0bd279ae2a8ec86074521f59c49eb3
DIFF: https://github.com/llvm/llvm-project/commit/846909e2ab0bd279ae2a8ec86074521f59c49eb3.diff

LOG: [lldb] Fix UBSan regression in GetSLEB128

It regressed recently by my: https://reviews.llvm.org/D81119

Added: 
    

Modified: 
    lldb/source/Utility/DataExtractor.cpp

Removed: 
    


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diff  --git a/lldb/source/Utility/DataExtractor.cpp b/lldb/source/Utility/DataExtractor.cpp
index 5f4abb82163e..023190b2ae91 100644
--- a/lldb/source/Utility/DataExtractor.cpp
+++ b/lldb/source/Utility/DataExtractor.cpp
@@ -930,8 +930,10 @@ int64_t DataExtractor::GetSLEB128(offset_t *offset_ptr) const {
     }
 
     // Sign bit of byte is 2nd high order bit (0x40)
-    if (shift < size && (byte & 0x40))
-      result |= -(static_cast<int64_t>(1) << shift);
+    if (shift < size && (byte & 0x40)) {
+      // -(static_cast<int64_t>(1) << 63) errors on the negation with UBSan.
+      result |= -(static_cast<uint64_t>(1) << shift);
+    }
 
     *offset_ptr += bytecount;
     return result;