[LLVMbugs] [Bug 6996] New: vtables marked weak_odr instead of linkonce_odr

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=6996

           Summary: vtables marked weak_odr instead of linkonce_odr
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: LLVM Codegen
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: clattner at apple.com
                CC: llvmbugs at cs.uiuc.edu


In this testcase:

struct A {
  virtual int f() { return 1; }
};

struct B {
  virtual int f() { return 2; }
};

struct C : A, B {
  virtual int f() { return 3; }
};

struct D : C {
  virtual int f() { return 4; }
};
//}

static int f(D* d) {
  B* b = d;
  return b->f();
};

int g() {
  D d;
  return f(&d);
}

The vtables and related gunk are emitted as weak_odr instead of linkonce_odr. 
Because the vtables will be emitted in each translation unit that could
possibly use them (they don't have a key function) they can be linkonce_odr. 
When llvm devirtualizes this example, we end up emitting all the vtables etc
even though they aren't used.

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