• d-bugmail puremagic.com (80/81) May 08 2020 https://issues.dlang.org/show_bug.cgi?id=20805

d-bugmail puremagic.com writes:

https://issues.dlang.org/show_bug.cgi?id=20805

          Issue ID: 20805
           Summary: C++ mangling mismatch with templates and namespaces
           Product: D
           Version: D2
          Hardware: x86_64
                OS: Windows
            Status: NEW
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: andrej.mitrovich gmail.com

Using DMD v2.091.1.

Take these two files:

cpp.cpp

-----
#include <vector>

static const uint32_t XDR_MAX_LEN = 0xfffffffc;

namespace xdr
{
    template<typename T, uint32_t N = XDR_MAX_LEN>
    struct xvector
    {
    };
}

template<typename T, typename VectorT>
void push_back(VectorT& this_, T& value)
{
}

#define PUSHBACKINST1(T) template void push_back<T, xdr::xvector<T>
(xdr::xvector<T>&, T&);

PUSHBACKINST1(xdr::xvector<unsigned char>)
-----

and d.d:

-----
import core.stdc.stdint;

extern (D) static immutable XDR_MAX_LEN = 0xffff_fffc;

extern (C++, `xdr`)
struct xvector(T, uint32_t N = XDR_MAX_LEN)
{
}

extern (C++)
public void push_back(T, VectorT) (ref VectorT this_, ref T value);

void main ()
{
    xvector!(xvector!ubyte) vec;
    xvector!ubyte val;
    vec.push_back(val);
}
-----

$ cl /JMC /MP /GS /c /Zc:forScope /std:c++14 cpp.cpp
$ dmd -m64 cpp.obj d.d

d.obj : error LNK2019: unresolved external symbol "void __cdecl
push_back<struct xdr::xvector<unsigned char,4294967292>,struct
xdr::xvector<struct xdr::xvector<unsigned char,4294967292>,4294967292> >(struct
xdr::xvector<struct xdr::xvector<unsigned char,4294967292>,4294967292> &,struct
xvector<unsigned char,4294967292>::xvector<unsigned char,4294967292> &)"
(??$push_back U?$xvector E$0PPPPPPPM  xdr  U?$xvector U?$xvector E$0PPPPPPPM  xdr  $0PPPPPPPM  2   YAXAEAU?$xvector U?$xvector E$0PPPPPPPM  xdr  $0PPPPPPPM  xdr  AEAU?$xvector E$0PPPPPPPM  2  Z)
referenced in function _Dmain
cpp.exe : fatal error LNK1120: 1 unresolved externals

The actual exported symbol is:

void __cdecl push_back<struct xdr::xvector<unsigned char,4294967292>,struct
xdr::xvector<struct xdr::xvector<unsigned char,4294967292>,4294967292> >(struct
xdr::xvector<struct xdr::xvector<unsigned char,4294967292>,4294967292> &,struct
xdr::xvector<unsigned char,4294967292> &)"
(??$push_back U?$xvector E$0PPPPPPPM  xdr  U?$xvector U?$xvector E$0PPPPPPPM  xdr  $0PPPPPPPM  2   YAXAEAU?$xvector U?$xvector E$0PPPPPPPM  xdr  $0PPPPPPPM  xdr  AEAU?$xvector E$0PPPPPPPM  1  Z)

The difference is at the very end.  2  Z in D vs  1  Z in C++.

It seems the namespace is not mangled properly.

Demangled D:

void __cdecl push_back<struct xdr::xvector<unsigned char,-4>,struct
xdr::xvector<struct xdr::xvector<unsigned char,-4>,-4> >(struct
xdr::xvector<struct xdr::xvector<unsigned char,-4>,-4> & __ptr64,struct
xvector<unsigned char,-4>::xvector<unsigned char,-4> & __ptr64)

Demangled C++:

void __cdecl push_back<struct xdr::xvector<unsigned char,-4>,struct
xdr::xvector<struct xdr::xvector<unsigned char,-4>,-4> >(struct
xdr::xvector<struct xdr::xvector<unsigned char,-4>,-4> & __ptr64,struct
xdr::xvector<unsigned char,-4> & __ptr64)

Notice the missing 'xdr::' close to the end.

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