Here's a minimal example:

  void r(T...)(T args) {}

  extern (C++) {
          void s(T...)(T args) { r(args); }
  }

  void main() {
          s(0);
  }

Traceback from GDC:

  cc1d: ../../gcc-6.3.0/gcc/d/dfrontend/cppmangle.c:185: void CppMangleVisitor::source_name(Dsymbol*, bool): Assertion `t' failed.
  minim.d: In function ‘D main’:
  minim.d:9:2: internal compiler error: Aborted
    s(0);
    ^
  0xb91c3f crash_signal
        ../../gcc-6.3.0/gcc/toplev.c:333
  0x5f4f26 CppMangleVisitor::source_name(Dsymbol*, bool)
        ../../gcc-6.3.0/gcc/d/dfrontend/cppmangle.c:185
  0x5f0b82 CppMangleVisitor::mangle_function(FuncDeclaration*)
        ../../gcc-6.3.0/gcc/d/dfrontend/cppmangle.c:462
  0x5f0b82 CppMangleVisitor::mangleOf(Dsymbol*)
        ../../gcc-6.3.0/gcc/d/dfrontend/cppmangle.c:575
  0x5f0b82 toCppMangle(Dsymbol*)
        ../../gcc-6.3.0/gcc/d/dfrontend/cppmangle.c:910
  0x67ba17 Mangler::visit(Declaration*)
        ../../gcc-6.3.0/gcc/d/dfrontend/mangle.c:421
  0x67a2f8 mangleExact(FuncDeclaration*)
        ../../gcc-6.3.0/gcc/d/dfrontend/mangle.c:877
  0x6ed183 get_symbol_decl(Declaration*)
        ../../gcc-6.3.0/gcc/d/d-decls.cc:164
  0x72ab78 ExprVisitor::visit(VarExp*)
        ../../gcc-6.3.0/gcc/d/expr.cc:2062
  0x7298ef build_expr(Expression*, bool)
        ../../gcc-6.3.0/gcc/d/expr.cc:2851
  0x72b759 ExprVisitor::visit(CallExp*)
        ../../gcc-6.3.0/gcc/d/expr.cc:1633
  0x7298ef build_expr(Expression*, bool)
        ../../gcc-6.3.0/gcc/d/expr.cc:2851
  0x729a5f build_expr_dtor(Expression*)
        ../../gcc-6.3.0/gcc/d/expr.cc:2895
  0x731d7c IRVisitor::visit(ExpStatement*)
        ../../gcc-6.3.0/gcc/d/toir.cc:649
  0x731bf8 IRVisitor::visit(CompoundStatement*)
        ../../gcc-6.3.0/gcc/d/toir.cc:665
  0x731b95 build_ir(FuncDeclaration*)
        ../../gcc-6.3.0/gcc/d/toir.cc:1037
  0x706d84 FuncDeclaration::toObjFile()
        ../../gcc-6.3.0/gcc/d/d-objfile.cc:1359
  0x7083a4 Module::genobjfile(bool)
        ../../gcc-6.3.0/gcc/d/d-objfile.cc:1465
  0x6e7f22 d_parse_file()
        ../../gcc-6.3.0/gcc/d/d-lang.cc:1215
  Please submit a full bug report,
  with preprocessed source if appropriate.
  Please include the complete backtrace with any bug report.
  See <http://gcc.gnu.org/bugs.html> for instructions.

On 28 December 2016 at 07:51, Elronnd via D.gnu <d.gnu@puremagic.com> wrote:
> Here's a minimal example:
>
>   void r(T...)(T args) {}
>
>   extern (C++) {
>           void s(T...)(T args) { r(args); }
>   }
>
>   void main() {
>           s(0);
>   }
>

It seems the bug is also in dmd too?  Unless it is fixed in master/latest release, in which case will need to find out when this happened.

On Saturday, 31 December 2016 at 15:10:36 UTC, Iain Buclaw wrote:
> On 28 December 2016 at 07:51, Elronnd via D.gnu <d.gnu@puremagic.com> wrote:
> *snip*
> It seems the bug is also in dmd too?  Unless it is fixed in master/latest release, in which case will need to find out when this happened.

It works fine for me on dmd.

On 8 January 2017 at 09:08, Elronnd via D.gnu <d.gnu@puremagic.com> wrote:
> On Saturday, 31 December 2016 at 15:10:36 UTC, Iain Buclaw wrote:
>>
>> On 28 December 2016 at 07:51, Elronnd via D.gnu <d.gnu@puremagic.com>
>> wrote:
>> *snip*
>> It seems the bug is also in dmd too?  Unless it is fixed in master/latest
>> release, in which case will need to find out when this happened.
>
>
> It works fine for me on dmd.

Then the version of dmd I have probably isn't new enough then.  If the latest is fine, then the C++ mangler just needs to be sync'd between the two codebases.  It's totally encapsulated, so is relatively straightforward, once you get over the D -> C++ conversion. ;-)

On 8 January 2017 at 11:06, Iain Buclaw <ibuclaw@gdcproject.org> wrote:
> On 8 January 2017 at 09:08, Elronnd via D.gnu <d.gnu@puremagic.com> wrote:
>> On Saturday, 31 December 2016 at 15:10:36 UTC, Iain Buclaw wrote:
>>>
>>> On 28 December 2016 at 07:51, Elronnd via D.gnu <d.gnu@puremagic.com>
>>> wrote:
>>> *snip*
>>> It seems the bug is also in dmd too?  Unless it is fixed in master/latest
>>> release, in which case will need to find out when this happened.
>>
>>
>> It works fine for me on dmd.
>
> Then the version of dmd I have probably isn't new enough then.  If the latest is fine, then the C++ mangler just needs to be sync'd between the two codebases.  It's totally encapsulated, so is relatively straightforward, once you get over the D -> C++ conversion. ;-)

Looks like this is the related bug in DMD: https://issues.dlang.org/show_bug.cgi?id=15372

On 8 January 2017 at 16:42, Iain Buclaw <ibuclaw@gdcproject.org> wrote:
> On 8 January 2017 at 11:06, Iain Buclaw <ibuclaw@gdcproject.org> wrote:
>> On 8 January 2017 at 09:08, Elronnd via D.gnu <d.gnu@puremagic.com> wrote:
>>> On Saturday, 31 December 2016 at 15:10:36 UTC, Iain Buclaw wrote:
>>>>
>>>> On 28 December 2016 at 07:51, Elronnd via D.gnu <d.gnu@puremagic.com>
>>>> wrote:
>>>> *snip*
>>>> It seems the bug is also in dmd too?  Unless it is fixed in master/latest
>>>> release, in which case will need to find out when this happened.
>>>
>>>
>>> It works fine for me on dmd.
>>
>> Then the version of dmd I have probably isn't new enough then.  If the latest is fine, then the C++ mangler just needs to be sync'd between the two codebases.  It's totally encapsulated, so is relatively straightforward, once you get over the D -> C++ conversion. ;-)
>
> Looks like this is the related bug in DMD: https://issues.dlang.org/show_bug.cgi?id=15372

Actually, no.  It's this bug that is related indirectly, as the C++ mangler sees a Tuple parameter '[int]', but with the patch applied, it flattens all tuples so we are just left with the Type 'int'.

https://issues.dlang.org/show_bug.cgi?id=7469

On 8 January 2017 at 18:23, Iain Buclaw <ibuclaw@gdcproject.org> wrote:
> On 8 January 2017 at 16:42, Iain Buclaw <ibuclaw@gdcproject.org> wrote:
>> On 8 January 2017 at 11:06, Iain Buclaw <ibuclaw@gdcproject.org> wrote:
>>> On 8 January 2017 at 09:08, Elronnd via D.gnu <d.gnu@puremagic.com> wrote:
>>>> On Saturday, 31 December 2016 at 15:10:36 UTC, Iain Buclaw wrote:
>>>>>
>>>>> On 28 December 2016 at 07:51, Elronnd via D.gnu <d.gnu@puremagic.com>
>>>>> wrote:
>>>>> *snip*
>>>>> It seems the bug is also in dmd too?  Unless it is fixed in master/latest
>>>>> release, in which case will need to find out when this happened.
>>>>
>>>>
>>>> It works fine for me on dmd.
>>>
>>> Then the version of dmd I have probably isn't new enough then.  If the latest is fine, then the C++ mangler just needs to be sync'd between the two codebases.  It's totally encapsulated, so is relatively straightforward, once you get over the D -> C++ conversion. ;-)
>>
>> Looks like this is the related bug in DMD: https://issues.dlang.org/show_bug.cgi?id=15372
>
> Actually, no.  It's this bug that is related indirectly, as the C++ mangler sees a Tuple parameter '[int]', but with the patch applied, it flattens all tuples so we are just left with the Type 'int'.
>
> https://issues.dlang.org/show_bug.cgi?id=7469

But of course there's a bug in the patch!

https://issues.dlang.org/show_bug.cgi?id=15789