Debugging SWIG %ignore

Question

I'm trying to get SWIG to %ignore a symbol like MyNamespace::SubNamespace::MyClass::operator->(). I've tried a million different combinations of %ignore:

• %ignore operator->;
• %ignore operator ->;
• %ignore operator ->();
• %ignore *::operator->;
• %ignore MyNamespace::SubNamespace::MyClass::operator->;

Hell even %ignore MyNamespace::SubNamespace::MyClass; doesn't seem to do anything. In every case I get this error:

...MyFile.hpp:267: Warning 508: Declaration of 'operator <' shadows declaration accessible via operator->(),
...MyFile.hpp:192: Warning 508: previous declaration of 'operator <'.

It's caused by this SWIG code, which seems to be something to do with smart pointers. However it looks from the code like %ignoreing the operator->() should remove the warning. In any case ignoring the entire class should.

So my question is, is there any way to debug %ignore. As far as I can see it looks like you have to just keep trying combinations until it works. Is there a way to print out SWIG's list of symbols? The code doesn't look like it has any logging facility.

Answer 1

Well I didn't find an option for %ignore specifically, but there are various -debug-... command line options. In particular -debug-symbols lead me to find that operator->() is %renamed to __deref__ in swig.swg which is included by default in all files.

I tried %ignore __deref__; and some variants but that doensn't work.

I even eventually modified the code to detect %ignores (hint:

/* Create a name applying rename/namewarn if needed */
static String *apply_rename(String *newname, int fullname, String *prefix, String *name) {
  String *result = 0;
  if (newname && Len(newname)) {
    if (Strcmp(newname, "$ignore") == 0) {
        printf("Renaming to ignore: %s\n", Char(name));
      result = Copy(newname);

) but none of those names seem to have namespaces. In fact, the warning about two operator<'s are in different classes (although one is a friend of the other) and as far as I can tell SWIG is just looking up if there are any other operator<'s. Could be a namespace bug.