Multiple-defined __destructor_1, __destructor_8 when building with recent clang-cl

Clang Frontend
#1

After a recent pull of LLVM/Clang trunk, my clang-cl build of LibreOffice on Windows started to fail to link some DLL because of __destructor_1 and __destructor_8 symbols defined in multiple objects.

I haven't been able yet to strip that down, and looking at the objects' assembler output it isn't clear to me what those symbols are emitted for.

Do those symbols maybe ring a bell for anybody? Is that some recent addition?

#2

Looks like Akira added a bunch of stuff for this in r326307. It is supposed to relate to ARC and __strong, __weak, etc. It’s pretty complex. :frowning:

That code does not appear to work for non-MachO. It creates LLVM IR functions directly without going through the usual CGM codepaths, so it doesn’t add a comdat.

#3

Looks like Akira added a bunch of stuff for this in r326307. It is supposed to relate to ARC and __strong, __weak, etc. It’s pretty complex. :frowning:

That code does not appear to work for non-MachO. It creates LLVM IR functions directly without going through the usual CGM codepaths, so it doesn’t add a comdat.

I would not have expected this patch to affect the compilation of ordinary C++ code.

John.

#4

r326307 and r327870 made changes that allow declaring ObjC __strong and __weak fields in C structs, so they shouldn’t have any effect if you are compiling your code in C++ mode. Is it possible to come up with a small C++ test case that causes clang to emit the destructor functions you are seeing?

#5

libc++

file: include/deque

1185
1186 template <class _Tp, class _Allocator /= allocator<_Tp>/>
1187 class _LIBCPP_TEMPLATE_VIS deque
1188 : private __deque_base<_Tp, _Allocator>
1189 {

Why is the deque’s Allocator default initializer commented?

I can write this code below:

#include
int main()
{
std::deque u;

return 0;
}

So, shouldn’t the default initializer be present there?

PS: May I do questions like this in this mailing list?

#6

This link
http://www.cplusplus.com/reference/deque/deque/

has:

template < class T, class Alloc = allocator<T> > class deque;

and this link
http://en.cppreference.com/w/cpp/container/deque
has

template<

class T,
class Allocator = std::allocator

class deque;

I dont understand two things:

1- Why is it working without parameter initialization?
2- Why the initialization was commented?

#7

I understood:

line 172:

template <class _Tp, class _Allocator = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS deque;

The declaration has the " = allocator<_Tp>".

Thanks, Topper.

#8

Filed <https://bugs.llvm.org/show_bug.cgi?id=37146> "clang-cl emits special functions for non-trivial C-structs ('__destructor_8') introduced for Objective-C" now, with reproducer.