[LLVMbugs] [Bug 20979] New: UBSan errors in llvm-cov (misaligned memory access)

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=20979

            Bug ID: 20979
           Summary: UBSan errors in llvm-cov (misaligned memory access)
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: vonosmas at gmail.com
                CC: llvm-bugs at justinbogner.com, llvmbugs at cs.uiuc.edu
            Blocks: 20815
    Classification: Unclassified

The following llvm-cov tests fail under UBSan bootstrap of LLVM:

    LLVM :: tools/llvm-cov/showExpansions.cpp
    LLVM :: tools/llvm-cov/showHighlightedRanges.cpp
    LLVM :: tools/llvm-cov/showLineExecutionCounts.cpp
    LLVM :: tools/llvm-cov/showRegionMarkers.cpp

The problem is misaligned access in CoverageMappingReader.

Example error report:
llvm/lib/ProfileData/CoverageMappingReader.cpp:349:17: runtime error: member
access within misaligned address 0x00000271f4fa for type 'const (anonymous
namespace)::CoverageMappingTURecord<unsigned long>', which requires 4 byte
alignment
0x00000271f4fa: note: pointer points here
 6d 61  69 6e 01 00 00 00 40 00  00 00 68 00 00 00 00 00  00 00 d0 20 00 00 01
00  00 00 04 00 00 00
              ^ 
    #0 0x7f985a in std::error_code readCoverageMappingData<unsigned
long>((anonymous namespace)::SectionData&, llvm::StringRef,
std::vector<llvm::coverage::ObjectFileCoverageMappingReader::ProfileMappingRecord,
std::allocator<llvm::coverage::ObjectFileCoverageMappingReader::ProfileMappingRecord>
>&, std::vector<llvm::StringRef, std::allocator<llvm::StringRef> >&)
llvm/lib/ProfileData/CoverageMappingReader.cpp:349:5
    #1 0x7f7e8c in
llvm::coverage::ObjectFileCoverageMappingReader::ObjectFileCoverageMappingReader(std::unique_ptr<llvm::MemoryBuffer,
std::default_delete<llvm::MemoryBuffer> >&, llvm::sys::fs::file_magic)
llvm/lib/ProfileData/CoverageMappingReader.cpp:455:11
    #2 0x45c915 in (anonymous namespace)::CodeCoverageTool::load()
llvm/tools/llvm-cov/CodeCoverage.cpp:388:3
    #3 0x456bf6 in (anonymous namespace)::CodeCoverageTool::show(int, char
const**, std::function<int (int, char const**)>)
llvm/tools/llvm-cov/CodeCoverage.cpp:611:7
    #4 0x44dd20 in (anonymous namespace)::CodeCoverageTool::run((anonymous
namespace)::CodeCoverageTool::Command, int, char const**)
llvm/tools/llvm-cov/CodeCoverage.cpp:558:12
    #5 0x44b1de in show_main(int, char const**)
llvm/tools/llvm-cov/CodeCoverage.cpp:702:10
    #6 0x41f8ae in main llvm/tools/llvm-cov/llvm-cov.cpp:55:14


To reproduce: build LLVM with just-built Clang and
-DLLVM_USE_SANITIZER=Undefined CMake option. I'm going to disable all llvm-cov
tests under UBSan in test/toools/llvm-cov/lit.local.cfg, so that suppression
will have to be removed as well.

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