[llvm-bugs] [Bug 39491] New: Creating a std::shared_ptr from OrcJit with clang fails

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=39491

            Bug ID: 39491
           Summary: Creating a std::shared_ptr from OrcJit with clang
                    fails
           Product: libraries
           Version: 7.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: OrcJIT
          Assignee: unassignedbugs at nondot.org
          Reporter: jeanmichael.celerier at gmail.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 21055
  --> https://bugs.llvm.org/attachment.cgi?id=21055&action=edit
code that reproduces the problem on linux

Hello,
I have the following problem, while trying to JIT-compile some C++ code with
clang under linux.

Basically, I have code that looks like this (full repro attached) :

```
struct blah
{
    virtual ~blah();
    virtual std::shared_ptr<zob> make() const = 0;
};

struct blah_impl : blah
{
    virtual ~blah_impl() { }
    virtual std::shared_ptr<zob> make() const { return std::make_shared<zob>();
}
};

extern "C" 
__attribute__((visibility("default"))) 
void* factory()
{ 
    return new blah_impl; 
}
``` 

e.g. an interface defined in my "host" program, which returns a shared_ptr. I
want to JIT-construct specific instances of my interface. Most parts work fine,
except shared_ptr : for some reason, the use_count of the created shared_ptr is
incorrect, which leads to fairly fast crashes.

UBSan complains with the following when running the sample code : 

```
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.2.1/../../../../include/c++/8.2.1/bits/shared_ptr_base.h:741:36:
runtime error: member call on address 0x6060002a1e80 which does not point to an
object of type 'std::_Sp_counted_base<__gnu_cxx::_S_atomic>'
0x6060002a1e80: note: object is of type 'std::_Sp_counted_ptr_inplace<zob,
std::allocator<zob>, (__gnu_cxx::_Lock_policy)1>'
 63 00 00 29  90 67 74 47 4a 7f 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00
00 00 00  00 00 00 00
              ^~~~~~~~~~~~~~~~~~~~~~~
              vptr for 'std::_Sp_counted_ptr_inplace<zob, std::allocator<zob>,
(__gnu_cxx::_Lock_policy)1>'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.2.1/../../../../include/c++/8.2.1/bits/shared_ptr_base.h:741:36
in 
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.2.1/../../../../include/c++/8.2.1/bits/shared_ptr_base.h:203:33:
runtime error: member access within address 0x6060002a1e80 which does not point
to an object of type 'const std::_Sp_counted_base<__gnu_cxx::_S_atomic>'
0x6060002a1e80: note: object is of type 'std::_Sp_counted_ptr_inplace<zob,
std::allocator<zob>, (__gnu_cxx::_Lock_policy)1>'
 63 00 00 29  90 67 74 47 4a 7f 00 00  00 00 00 00 00 00 00 00  00 00 00 00 00
00 00 00  00 00 00 00
              ^~~~~~~~~~~~~~~~~~~~~~~
              vptr for 'std::_Sp_counted_ptr_inplace<zob, std::allocator<zob>,
(__gnu_cxx::_Lock_policy)1>'
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/8.2.1/../../../../include/c++/8.2.1/bits/shared_ptr_base.h:203:33
in 
```

This looks like an ABI problem but I am compiling everything with libstdc++, in
the same c++ mode. Most objects passed from the JIT to the host seem to work
fine (vectors, strings, etc), as well as language things that may be impacted
by ABI changes (e.g. destructors). What is going wrong then ?

Thanks

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