[llvm-bugs] [Bug 28338] New: False positive: analyzer believes a value is garbage/undefined

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=28338

            Bug ID: 28338
           Summary: False positive: analyzer believes a value is
                    garbage/undefined
           Product: clang
           Version: 3.8
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Static Analyzer
          Assignee: kremenek at apple.com
          Reporter: mactalla.obair at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 16645
  --> https://llvm.org/bugs/attachment.cgi?id=16645&action=edit
False positive test case

When reading an individual byte from a larger value, the static analyzer is
fine if:
a) reading any byte if the source is a uint32_t
b) reading the first byte if the source is a uint32_t[1]

But it falsely reports a problem if reading a subsequent byte from uint32_t[1]

The attached test case demonstrates good (silent) behaviour with VARIANT= 1, 2
and 3.  And exposes the false positive with VARIANT=4.

I also tested with clang-3.7 and clang-3.6, so it's not a regression.

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