#1328 swig typedef decomposition problem

[Florian]

Hi,

I discovered some strange generation when using the following simplified interface. The generated code cannot be compiled because some reference is created without assignment, see below for more details.

%module test

%inline %{

  template<class T>
  class Vector
  {
    public:
      typedef T value;
      typedef value const & const_ref;

      Vector(const_ref A)
      {

      }

      ~Vector()
      {

      }
  };

  enum TestEnum;
%}

%template(VecTestNum) Vector<TestEnum>;

Generates some strange new function:

SWIGINTERN PyObject *_wrap_new_VecTestNum(PyObject *SWIGUNUSEDPARM(self), PyObject *args) {
  PyObject *resultobj = 0;
  Vector< enum TestEnum >::value *arg1 = 0 ;
  int val1 ;
  int ecode1 ;
  Vector< enum TestEnum >::const_ref temp1 ; /* here a const ref without definition of the variable will be created */
  PyObject * obj0 = 0 ;
  Vector< TestEnum > *result = 0 ;
...

Swig version: 2.0.10
Swig command: swig -python -c++ test.i

[Florian]

Could be same issue as https://sourceforge.net/p/swig/bugs/1304/. The snippet was working with 2.0.1, but not with 2.0.10. It seems the patch didn't find the way to 2.0.10, if it's the same issue.

[Olly Betts]

Reproduced with SWIG git master.

[Olly Betts]

Still reproduces with current git master (b18b75369cd4b2795abad1283629b13a62630b58)

[Olly Betts]

(Though the testcase needs tweaking slightly to actually define the enum (e.g. enum TestEnum { TESTENUM };) or else compilation gives an error:

test_wrap.cxx:3159:8: error: use of enum ‘TestEnum’ without previous declaration
 3159 |   enum TestEnum;
      |        ^~~~~~~~

with that adjustment the generated wrapper fails to compile with:

g++ `python3-config --cflags` -fPIC -c test_wrap.cxx -o test_wrap.o
test_wrap.cxx: In function ‘PyObject* _wrap_new_VecTestNum(PyObject*, PyObject*)’:
test_wrap.cxx:3327:38: error: ‘temp1’ declared as reference but not initialized
 3327 |   Vector< enum TestEnum >::const_ref temp1 ;
      |                                      ^~~~~
test_wrap.cxx:3337:13: error: invalid ‘static_cast’ from type ‘int’ to type ‘Vector<TestEnum>::const_ref’ {aka ‘const TestEnum&’}
 3337 |     temp1 = static_cast< Vector< enum TestEnum >::const_ref >(val1);
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test_wrap.cxx:3338:12: error: invalid conversion from ‘const Vector<TestEnum>::value*’ {aka ‘const TestEnum*’} to ‘Vector<TestEnum>::value*’ {aka ‘TestEnum*’} [-fpermissive]
 3338 |     arg1 = &temp1;
      |            ^~~~~~
      |            |
      |            const Vector<TestEnum>::value* {aka const TestEnum*}

)