[PATCH v2 3/3] Port libstdc++ pretty-printers to Python 2 + Python 3

[Samuel Bronson <naesten at gmail dot com>]

Loosely based on Mathias Klose' earlier patch
<http://patchwork.ozlabs.org/patch/287368/>.

Tested with:

$ make check-target-libstdc++-v3 RUNTESTFLAGS='--directory libstdc++-prettyprinters'

libstdc++-v3/

	PR libstdc++/58962
	* python/libstdcxx/v6/printers.py: Port to Python 2+3
	  (imap): New compat function.
	  (izip): Likewise.
	  (Iterator): New mixin to allow writing iterators in Python 3 style
	  regardless of which version we're running on.
	  [Python3] (long) New compat alias for "int".
	* testsuite/lib/gdb-test.exp: Port to Python 2+3 (print syntax)

Signed-off-by: Mathias Klose <doko@ubuntu.com>
Signed-off-by: Samuel Bronson <naesten@gmail.com>
---
 libstdc++-v3/python/libstdcxx/v6/printers.py | 110 +++++++++++++++++++--------
 libstdc++-v3/testsuite/lib/gdb-test.exp      |   4 +-
 2 files changed, 79 insertions(+), 35 deletions(-)

diff --git a/libstdc++-v3/python/libstdcxx/v6/printers.py b/libstdc++-v3/python/libstdcxx/v6/printers.py
index 623a815..313b08d 100644
--- a/libstdc++-v3/python/libstdcxx/v6/printers.py
+++ b/libstdc++-v3/python/libstdcxx/v6/printers.py
@@ -1,4 +1,4 @@
-# Pretty-printers for libstc++.
+# Pretty-printers for libstdc++.
 
 # Copyright (C) 2008-2014 Free Software Foundation, Inc.
 
@@ -18,6 +18,50 @@
 import gdb
 import itertools
 import re
+import sys
+
+### Python 2 + Python 3 compatability code
+
+# Resources about compatability:
+#
+#  * <http://pythonhosted.org/six/>: Documentation of the "six" module
+
+# FIXME: The handling of e.g. std::basic_string (at least on char)
+# probably needs updating to work with Python 3's new string rules.
+#
+# In particular, Python 3 has a separate type (called byte) for
+# bytestrings, and a special b"" syntax for the byte literals; the old
+# str() type has been redefined to always store Unicode text.
+#
+# We probably can't do much about this until GDB get their act
+# together: <https://sourceware.org/bugzilla/show_bug.cgi?id=17138>
+
+if sys.version_info[0] > 2:
+    ### Python 3 stuff
+    Iterator = object
+    # Python 3 folds these into the normal functions.
+    imap = map
+    izip = zip
+    # Also, int subsumes long
+    long = int
+else:
+    ### Python 2 stuff
+    class Iterator:
+        """Compatability mixin for iterators
+
+        Instead of writing next() methods for iterators, write
+        __next__() methods and use this mixin to make them work in
+        Python 2 as well as Python 3.
+
+        Idea stolen from the "six" documentation:
+        <http://pythonhosted.org/six/#six.Iterator>
+        """
+
+        def next(self):
+            return self.__next__()
+
+    # In Python 2, we still need these from itertools
+    from itertools import imap, izip
 
 # Try to use the new-style pretty-printing if available.
 _use_gdb_pp = True
@@ -87,7 +131,7 @@ class UniquePointerPrinter:
 class StdListPrinter:
     "Print a std::list"
 
-    class _iterator:
+    class _iterator(Iterator):
         def __init__(self, nodetype, head):
             self.nodetype = nodetype
             self.base = head['_M_next']
@@ -97,7 +141,7 @@ class StdListPrinter:
         def __iter__(self):
             return self
 
-        def next(self):
+        def __next__(self):
             if self.base == self.head:
                 raise StopIteration
             elt = self.base.cast(self.nodetype).dereference()
@@ -135,7 +179,7 @@ class StdListIteratorPrinter:
 class StdSlistPrinter:
     "Print a __gnu_cxx::slist"
 
-    class _iterator:
+    class _iterator(Iterator):
         def __init__(self, nodetype, head):
             self.nodetype = nodetype
             self.base = head['_M_head']['_M_next']
@@ -144,7 +188,7 @@ class StdSlistPrinter:
         def __iter__(self):
             return self
 
-        def next(self):
+        def __next__(self):
             if self.base == 0:
                 raise StopIteration
             elt = self.base.cast(self.nodetype).dereference()
@@ -180,7 +224,7 @@ class StdSlistIteratorPrinter:
 class StdVectorPrinter:
     "Print a std::vector"
 
-    class _iterator:
+    class _iterator(Iterator):
         def __init__ (self, start, finish, bitvec):
             self.bitvec = bitvec
             if bitvec:
@@ -198,7 +242,7 @@ class StdVectorPrinter:
         def __iter__(self):
             return self
 
-        def next(self):
+        def __next__(self):
             count = self.count
             self.count = self.count + 1
             if self.bitvec:
@@ -265,7 +309,7 @@ class StdVectorIteratorPrinter:
 class StdTuplePrinter:
     "Print a std::tuple"
 
-    class _iterator:
+    class _iterator(Iterator):
         def __init__ (self, head):
             self.head = head
 
@@ -282,7 +326,7 @@ class StdTuplePrinter:
         def __iter__ (self):
             return self
 
-        def next (self):
+        def __next__ (self):
             nodes = self.head.type.fields ()
             # Check for further recursions in the inheritance tree.
             if len (nodes) == 0:
@@ -341,7 +385,7 @@ class StdStackOrQueuePrinter:
             return self.visualizer.display_hint ()
         return None
 
-class RbtreeIterator:
+class RbtreeIterator(Iterator):
     def __init__(self, rbtree):
         self.size = rbtree['_M_t']['_M_impl']['_M_node_count']
         self.node = rbtree['_M_t']['_M_impl']['_M_header']['_M_left']
@@ -353,7 +397,7 @@ class RbtreeIterator:
     def __len__(self):
         return int (self.size)
 
-    def next(self):
+    def __next__(self):
         if self.count == self.size:
             raise StopIteration
         result = self.node
@@ -422,7 +466,7 @@ class StdMapPrinter:
     "Print a std::map or std::multimap"
 
     # Turn an RbtreeIterator into a pretty-print iterator.
-    class _iter:
+    class _iter(Iterator):
         def __init__(self, rbiter, type):
             self.rbiter = rbiter
             self.count = 0
@@ -431,9 +475,9 @@ class StdMapPrinter:
         def __iter__(self):
             return self
 
-        def next(self):
+        def __next__(self):
             if self.count % 2 == 0:
-                n = self.rbiter.next()
+                n = next(self.rbiter)
                 n = n.cast(self.type).dereference()
                 n = get_value_from_Rb_tree_node(n)
                 self.pair = n
@@ -465,7 +509,7 @@ class StdSetPrinter:
     "Print a std::set or std::multiset"
 
     # Turn an RbtreeIterator into a pretty-print iterator.
-    class _iter:
+    class _iter(Iterator):
         def __init__(self, rbiter, type):
             self.rbiter = rbiter
             self.count = 0
@@ -474,8 +518,8 @@ class StdSetPrinter:
         def __iter__(self):
             return self
 
-        def next(self):
-            item = self.rbiter.next()
+        def __next__(self):
+            item = next(self.rbiter)
             item = item.cast(self.type).dereference()
             item = get_value_from_Rb_tree_node(item)
             # FIXME: this is weird ... what to do?
@@ -541,7 +585,7 @@ class StdBitsetPrinter:
 class StdDequePrinter:
     "Print a std::deque"
 
-    class _iter:
+    class _iter(Iterator):
         def __init__(self, node, start, end, last, buffer_size):
             self.node = node
             self.p = start
@@ -553,7 +597,7 @@ class StdDequePrinter:
         def __iter__(self):
             return self
 
-        def next(self):
+        def __next__(self):
             if self.p == self.last:
                 raise StopIteration
 
@@ -638,7 +682,7 @@ class StdStringPrinter:
     def display_hint (self):
         return 'string'
 
-class Tr1HashtableIterator:
+class Tr1HashtableIterator(Iterator):
     def __init__ (self, hash):
         self.buckets = hash['_M_buckets']
         self.bucket = 0
@@ -654,7 +698,7 @@ class Tr1HashtableIterator:
     def __iter__ (self):
         return self
 
-    def next (self):
+    def __next__ (self):
         if self.node == 0:
             raise StopIteration
         node = self.node.cast(self.node_type)
@@ -669,7 +713,7 @@ class Tr1HashtableIterator:
                 self.bucket = self.bucket + 1
         return result
 
-class StdHashtableIterator:
+class StdHashtableIterator(Iterator):
     def __init__(self, hash):
         self.node = hash['_M_before_begin']['_M_nxt']
         self.node_type = find_type(hash.type, '__node_type').pointer()
@@ -677,7 +721,7 @@ class StdHashtableIterator:
     def __iter__(self):
         return self
 
-    def next(self):
+    def __next__(self):
         if self.node == 0:
             raise StopIteration
         elt = self.node.cast(self.node_type).dereference()
@@ -706,10 +750,10 @@ class Tr1UnorderedSetPrinter:
         return '[%d]' % i
 
     def children (self):
-        counter = itertools.imap (self.format_count, itertools.count())
+        counter = imap (self.format_count, itertools.count())
         if self.typename.startswith('std::tr1'):
-            return itertools.izip (counter, Tr1HashtableIterator (self.hashtable()))
-        return itertools.izip (counter, StdHashtableIterator (self.hashtable()))
+            return izip (counter, Tr1HashtableIterator (self.hashtable()))
+        return izip (counter, StdHashtableIterator (self.hashtable()))
 
 class Tr1UnorderedMapPrinter:
     "Print a tr1::unordered_map"
@@ -741,15 +785,15 @@ class Tr1UnorderedMapPrinter:
         return '[%d]' % i
 
     def children (self):
-        counter = itertools.imap (self.format_count, itertools.count())
+        counter = imap (self.format_count, itertools.count())
         # Map over the hash table and flatten the result.
         if self.typename.startswith('std::tr1'):
-            data = self.flatten (itertools.imap (self.format_one, Tr1HashtableIterator (self.hashtable())))
+            data = self.flatten (imap (self.format_one, Tr1HashtableIterator (self.hashtable())))
             # Zip the two iterators together.
-            return itertools.izip (counter, data)
-        data = self.flatten (itertools.imap (self.format_one, StdHashtableIterator (self.hashtable())))
+            return izip (counter, data)
+        data = self.flatten (imap (self.format_one, StdHashtableIterator (self.hashtable())))
         # Zip the two iterators together.
-        return itertools.izip (counter, data)
+        return izip (counter, data)
         
 
     def display_hint (self):
@@ -758,7 +802,7 @@ class Tr1UnorderedMapPrinter:
 class StdForwardListPrinter:
     "Print a std::forward_list"
 
-    class _iterator:
+    class _iterator(Iterator):
         def __init__(self, nodetype, head):
             self.nodetype = nodetype
             self.base = head['_M_next']
@@ -767,7 +811,7 @@ class StdForwardListPrinter:
         def __iter__(self):
             return self
 
-        def next(self):
+        def __next__(self):
             if self.base == 0:
                 raise StopIteration
             elt = self.base.cast(self.nodetype).dereference()
diff --git a/libstdc++-v3/testsuite/lib/gdb-test.exp b/libstdc++-v3/testsuite/lib/gdb-test.exp
index 6d7ea9d..9cb6ecf 100644
--- a/libstdc++-v3/testsuite/lib/gdb-test.exp
+++ b/libstdc++-v3/testsuite/lib/gdb-test.exp
@@ -91,7 +91,7 @@ proc gdb-test { marker {selector {}} } {
 	}
     }
 
-    set do_whatis_tests [gdb_batch_check "python print gdb.type_printers" \
+    set do_whatis_tests [gdb_batch_check "python print(gdb.type_printers)" \
 			   "\\\[\\\]"]
     if {!$do_whatis_tests} {
 	send_log "skipping 'whatis' tests - gdb too old"
@@ -259,6 +259,6 @@ proc gdb_batch_check {command pattern} {
 # but not earlier versions.
 # Return 1 if the version is ok, 0 otherwise.
 proc gdb_version_check {} {
-    return [gdb_batch_check "python print gdb.lookup_global_symbol" \
+    return [gdb_batch_check "python print(gdb.lookup_global_symbol)" \
 	      "<built-in function lookup_global_symbol>"]
 }