[llvm-bugs] [Bug 30737] New: Half-baked clang warning about address of members of packed structs

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=30737

            Bug ID: 30737
           Summary: Half-baked clang warning about address of members of
                    packed structs
           Product: new-bugs
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: new bugs
          Assignee: unassignedbugs at nondot.org
          Reporter: stark at mit.edu
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

Created attachment 17461
  --> https://llvm.org/bugs/attachment.cgi?id=17461&action=edit
Minimal test case with actual code from production

I'm using clang 4.0 on Debian and getting spurious "address-of-packed-member"
warnings.

The struct in question is declared with 

  __attribute__((packed))
  __attribute__((aligned(2)))

and consists of three unsigned shorts. 

So it seems the warning is triggering without regard to the actual alignment of
the struct and its members and without regard to the actual storage aligment of
the struct. 



$ /usr/bin/clang-4.0 -v 
clang version 4.0.0-svn283054-1~exp1 (trunk)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/6.2.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.0
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/6.2.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.4.1
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.2.0
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.2.0
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

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