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digitalmars.D.bugs - [Issue 21283] New: [C++] Wrong mangling for ref of parameter pack


          Issue ID: 21283
           Summary: [C++] Wrong mangling for ref of parameter pack
           Product: D
           Version: D2
          Hardware: All
                OS: Linux
            Status: NEW
          Keywords: C++, industry
          Severity: major
          Priority: P1
         Component: dmd
          Assignee: nobody puremagic.com
          Reporter: pro.mathias.lang gmail.com

C++ code:
template<typename T, typename ...Args>
void make_shared_poc (Args&... args) {}
template void make_shared_poc<int, int, int>(int&, int&);

Compiled with `g++ -std=c++11 test.cpp` gives:
$ nm test.o
0000000000000000 T __Z15make_shared_pocIiJiiEEvDpRT0_

Now the equivalent D code:
extern(C++) void make_shared_poc (T, Args...)  (ref Args args);
void foobar() { int a, b; make_shared_poc!(int, int, int)(a, b); }

Compiled with `dmd -extern-std=c++11 -c test.d` (DMD v2.094.0):
                 U __Z15make_shared_pocIiJiiEEvRDpT0_

Notice that in the C++ code, `R` comes after `Dq` (ref is part of the type),
while in the D code, `R` comes before.
See https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangle.function-type :
 When a function parameter is a C++11 function parameter pack, its type is
mangled with Dp <type>, i.e., its type is a pack expansion:

Sep 28 2020