[Xapian-tickets] [Xapian] #448: Allow usage of custom stemmers

[Xapian]

#448: Allow usage of custom stemmers
-------------------------+--------------------------------------------------
 Reporter:  esizikov     |        Owner:  olly    
     Type:  enhancement  |       Status:  reopened
 Priority:  normal       |    Milestone:  1.2.x   
Component:  Library API  |      Version:  1.0.17  
 Severity:  normal       |   Resolution:          
 Keywords:               |    Blockedby:          
 Platform:  All          |     Blocking:          
-------------------------+--------------------------------------------------

Comment(by esizikov):

 If we'd like to be able to subclass our own stemmer in the SWIG-wrapped
 languages we need the {{{Xapian::StemImplementation}}} to be a "director":
 {{{%feature("director") Xapian::StemImplementation;}}}

 This doesn't work and the SWIG fails with
 {{{
 /home/esizikov/svn/xapian/xapian-core/include/xapian/stem.h:41:
 Warning(473): Returning a pointer or reference in a director method is not
 recommended.
 }}}

 When trying to enable the "director" feature for the only {{{operator()}}}
 we really need from this interface class (like {{{%feature("director")
 Xapian::StemImplementation::operator();}}}) I've got the error like:
 {{{
 modern/xapian_wrap.cc:34173: error: '_swig_thread_allow' was not declared
 in this scope
 }}}

 In the generated modern/xapian_wrap.cc we have:
 {{{
 #!cpp
 ...
   director = SWIG_DIRECTOR_CAST(arg1);
   upcall = (director && (director->swig_get_self()==swig_obj[0]));
   try {
     {
       try {
         if (upcall) {
 Swig::DirectorPureVirtualException::raise("Xapian::StemImplementation::operator
 ()");
         } else {
           result = (arg1)->operator ()((std::string const &)*arg2);
         }
       } catch (...) {
         SWIG_PYTHON_THREAD_END_ALLOW;
         Xapian::SetPythonException();
         SWIG_fail;
       }
     }
   } catch (Swig::DirectorException&) {
     SWIG_fail;
   }
 ...
 }}}

 As you can see {{{SWIG_PYTHON_THREAD_END_ALLOW;}}} is used without a
 proper initialization. It would be OK if the generated code looks like
 this:
 {{{
 #!cpp
 ...
   director = SWIG_DIRECTOR_CAST(arg1);
   upcall = (director && (director->swig_get_self()==swig_obj[0]));
   try {
     SWIG_PYTHON_THREAD_BEGIN_ALLOW;
     {
       try {
         if (upcall) {
 Swig::DirectorPureVirtualException::raise("Xapian::StemImplementation::operator
 ()");
         } else {
           result = (arg1)->operator ()((std::string const &)*arg2);
         }
       } catch (...) {
         SWIG_PYTHON_THREAD_END_ALLOW;
         Xapian::SetPythonException();
         SWIG_fail;
       }
     }
     SWIG_PYTHON_THREAD_END_ALLOW;
   } catch (Swig::DirectorException&) {
     SWIG_fail;
   }
 ...
 }}}

 Seems like be a SWIG bug.

-- 
Ticket URL: <http://trac.xapian.org/ticket/448#comment:20>
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