[llvm-bugs] [Bug 42756] New: Crash after explicit call to a base constructor with virtual base

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=42756

            Bug ID: 42756
           Summary: Crash after explicit call to a base constructor with
                    virtual base
           Product: clang
           Version: 8.0
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: C++
          Assignee: unassignedclangbugs at nondot.org
          Reporter: securesneakers at gmail.com
                CC: blitzrakete at gmail.com, dgregor at apple.com,
                    erik.pilkington at gmail.com, llvm-bugs at lists.llvm.org,
                    richard-llvm at metafoo.co.uk

Created attachment 22289
  --> https://bugs.llvm.org/attachment.cgi?id=22289&action=edit
Minimal example that reproduces the issue

The code below crashes Windows:

struct interface { };
struct base1_if : virtual interface { };
struct base2_if : virtual interface { };
struct base_if : base1_if, base2_if { };

struct derived : base_if {
    derived()
        : base_if()
    { }
};

int main() { derived d; }

Command line:
$ clang-cl -v
clang version 8.0.0 (tags/RELEASE_800/final)
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: C:\Program Files\LLVM\bin
$ clang-cl main.cpp
$ main.exe

Few notes:
- Removing explicit call to "base_if" avoids the issue.
- Generated assembly contains "memset(addr, 0, r8,0FFFFFFFFFFFFFFF8h)":

        00007FF7482310A9  mov         r8,0FFFFFFFFFFFFFFF8h  
        00007FF7482310B0  mov         dword ptr [rsp+2Ch],eax  
        00007FF7482310B4  call        memset (07FF748232FE0h)

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