[LLVMbugs] [Bug 18845] New: MS ABI: Incorrect this adjustment in base dtor when dtor is in non-primary vftable

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=18845

            Bug ID: 18845
           Summary: MS ABI: Incorrect this adjustment in base dtor when
                    dtor is in non-primary vftable
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: rnk at google.com
                CC: dgregor at apple.com, llvmbugs at cs.uiuc.edu
            Blocks: 12477
    Classification: Unclassified

When the primary base lacks a virtual destructor and a non-primary base has
one, we add this adjustments in destructor variants that don't require them.

This test case exhibits the problem:

$ cat t.cpp
int count;
struct A { 
  virtual void f() {}
};
struct B {
  virtual ~B() {
    count += b;
  }
  int b;
};
struct C : A, B {
  virtual ~C() {
    count += c;
  }
  int c;
};
int main() {
  C *p = new C();
  p->b = 2;
  p->c = 3;
  delete p;
  return count;
}

$ cl t.cpp && ./t.exe ; echo $?
5

$ clang-cl t.cpp && ./t.exe ; echo $?
127 (crash?)

The problem is that we emit this adjustments in *all* destructor variants,
rather than just the variant installed in the vftable:

$ clang-cl -GR- t.cpp -c && dumpbin /disasm t.obj | grep -B8 FFFFC
??_EC@@W3AEPAXI at Z ([thunk]:public: virtual void * __thiscall C::`vector
deleting destructor'`adjustor{4}' (unsigned int)):
  00000000: 55                 push        ebp
  00000001: 89 E5              mov         ebp,esp
  00000003: 83 EC 0C           sub         esp,0Ch
  00000006: 8B 45 08           mov         eax,dword ptr [ebp+8]
  00000009: 89 45 FC           mov         dword ptr [ebp-4],eax
  0000000C: 89 4D F8           mov         dword ptr [ebp-8],ecx
  0000000F: 8B 45 FC           mov         eax,dword ptr [ebp-4]
  00000012: 83 C1 FC           add         ecx,0FFFFFFFCh
--

??_GC@@UAEPAXI at Z (public: virtual void * __thiscall C::`scalar deleting
destructor'(unsigned int)):
  00000000: 55                 push        ebp
  00000001: 89 E5              mov         ebp,esp
  00000003: 83 EC 14           sub         esp,14h
  00000006: 8B 45 08           mov         eax,dword ptr [ebp+8]
  00000009: 81 C1 FC FF FF FF  add         ecx,0FFFFFFFCh
--

??1C@@UAE at XZ (public: virtual __thiscall C::~C(void)):
  00000000: 55                 push        ebp
  00000001: 89 E5              mov         ebp,esp
  00000003: 50                 push        eax
  00000004: 89 C8              mov         eax,ecx
  00000006: 83 C0 FC           add         eax,0FFFFFFFCh

Only the vector deleting destructor should do any adjustment.

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