[LLVMbugs] [Bug 21580] New: Undefined behavior in readEncodedPointer()

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=21580

            Bug ID: 21580
           Summary: Undefined behavior in readEncodedPointer()
           Product: libc++abi
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: All Bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: eric at efcs.ca
                CC: llvmbugs at cs.uiuc.edu, mclow.lists at gmail.com
    Classification: Unclassified

The following error occurs almost everywhere libc++abi is used with UBSAN. 


libcxxabi/src/cxa_personality.cpp:252:18: runtime error: load of misaligned
address 0x000000428c39 for type 'uint32_t' (aka 'unsigned int'), which requires
4 byte alignment
0x000000428c39: note: pointer points here
 03 35 03  27 00 00 00 00 22 00 00  00 00 00 00 00 00 22 00  00 00 13 00 00 00
3a 00  00 00 03 35 00

To recreate this error configure libc++abi with -DLLVM_USE_SANITIZER=Undefined
and run the libc++abi test suite. There will be multiple failures caused by
this.

I also tried running libc++'s testsuite with libcxxrt and UBSAN. I found that
the exact same error occurred in libcxxrt's implementation of reading an
encoded pointer.

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