[Pyrex] SystemError: error return without exception set

[Gary Bishop]

I think I may have found a bug in pyrex 0.9 on WindowsXP. I'm writing a 
__setitem__ handler for my extension class. When I run it, I get 
"SystemError: error return without exception set".  Looking at the 
generated C, I see that __pyx_r is apparently the return value and it 
is not initialized. It gets set near the bottom of the C function like this:

  __pyx_L30:;

  __pyx_r = 0;
  goto __pyx_L0;
  __pyx_L1:;
  Py_XDECREF(__pyx_3);
  Py_XDECREF(__pyx_4);
  __Pyx_AddTraceback("fmatrix.fmatrix.__setitem__");
  __pyx_r = -1;
  __pyx_L0:;
  Py_DECREF(__pyx_v_avalue);
  Py_DECREF(__pyx_v_r);
  Py_DECREF(__pyx_v_c);
  Py_DECREF(__pyx_v_self);
  Py_DECREF(__pyx_v_key);
  Py_DECREF(__pyx_v_value);
  return __pyx_r;

I'm guessing that a normal return should goto __pyx_L30, and an error 
return should goto __pyx_L1.

In my pyrex code I say:

    if PyInt_Check(key): # int index, simple and common
      i = key
      if i < 0:
        i = i + self.len
      if 0 <= i < self.len:
        if svalue:
          self.base[i] = fvalue
          return
        else:
          raise TypeError
      else:
        raise IndexError

The return gets translated into "goto __pyx_L0;" which skips the 
initialization of __pyx_r. I verified this by hacking the C code to 
initialize __pyx_r = 0 when it is declared. Then the function works as 
expected. So the problem *may* be that __pyx_r was supposed to be set 
before the goto, or it may be that the goto was supposed to be to 
__pyx_L30 instead of 0.

I can try to boil the code down to the minimum error producing subset 
if you need it.

gb