From 0bde41446a27a97f71ef0de16c4d45fa8cc7680b Mon Sep 17 00:00:00 2001
From: Matthias Koefferlein <matthias@koefferlein.de>
Date: Tue, 16 Apr 2019 23:54:11 +0200
Subject: [PATCH] Fixed #261 (iterator must not be incremented while value is
 used)

---
 src/pya/pya/pyaHelpers.cc | 16 +++++++++++++---
 src/pya/pya/pyaHelpers.h  |  1 +
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/pya/pya/pyaHelpers.cc b/src/pya/pya/pyaHelpers.cc
index 01e4858ac..399c26776 100644
--- a/src/pya/pya/pyaHelpers.cc
+++ b/src/pya/pya/pyaHelpers.cc
@@ -357,7 +357,18 @@ pya_plain_iterator_next (PyObject *self)
 {
   PYAIteratorObject *iter = (PYAIteratorObject *) self;
 
-  if (! iter->iter || iter->iter->at_end ()) {
+  if (! iter->iter) {
+    PyErr_SetNone (PyExc_StopIteration);
+    return NULL;
+  }
+
+  //  increment on first visit
+  if (! iter->first) {
+    iter->iter->inc ();
+  }
+  iter->first = false;
+
+  if (iter->iter->at_end ()) {
     PyErr_SetNone (PyExc_StopIteration);
     return NULL;
   }
@@ -369,8 +380,6 @@ pya_plain_iterator_next (PyObject *self)
   iter->iter->get (args);
   PythonRef obj = pop_arg (*iter->value_type, args, 0, heap);
 
-  iter->iter->inc ();
-
   return obj.release ();
 }
 
@@ -426,6 +435,7 @@ PYAIteratorObject::create (PyObject *origin, gsi::IterAdaptorAbstractBase *iter,
     iter_obj->origin = origin;
     iter_obj->iter = iter;
     iter_obj->value_type = value_type;
+    iter_obj->first = true;
   }
   return iter_obj;
 }
diff --git a/src/pya/pya/pyaHelpers.h b/src/pya/pya/pyaHelpers.h
index 9bfac61c1..e9afa8611 100644
--- a/src/pya/pya/pyaHelpers.h
+++ b/src/pya/pya/pyaHelpers.h
@@ -101,6 +101,7 @@ struct PYAIteratorObject
   static PYAIteratorObject *create (PyObject *origin, gsi::IterAdaptorAbstractBase *iter, const gsi::ArgType *value_type);
 
   PyObject *origin;
+  bool first;
   gsi::IterAdaptorAbstractBase *iter;
   const gsi::ArgType *value_type;