Re: [PATCH] libstdc++/77645 fix deque and vector xmethods for Python 3

[Jonathan Wakely]

On 20/09/16 09:41 +0100, Jonathan Wakely wrote:

On 19/09/16 21:39 +, Joseph Myers wrote:

On Mon, 19 Sep 2016, Jonathan Wakely wrote:


On 19/09/16 17:24 +, Joe Buck wrote:

Python has a distinct integer division operator, "//".  7 // 3 returns the
integer 2.


Python 3 does, but Python 2 doesn't have it unless you import it from
__future, and I don't know how far back that works. I don't want to
introduce a fix for Python 3 that breaks it for old systems.


No, // is available in Python, without needing __future__, from 2.2
onwards.


I stand corrected, thanks both of you.

I'll test and commnit this then.


I still need a cast in one place, because gdb.Value doesn't support
the // operator (https://sourceware.org/PR20624).

Tested x86_64-linux, committed to all branches.

commit c5abd6b08844bb626ea3f3df9e33bb2b97829624
Author: Jonathan Wakely 
Date:   Tue Sep 20 10:50:55 2016 +0100

Replace casts with floordiv operator in Python xmethods

	* python/libstdcxx/v6/xmethods.py (DequeWorkerBase.__init__)
	(DequeWorkerBase.index, VectorWorkerBase.get): Use // for division.

diff --git a/libstdc++-v3/python/libstdcxx/v6/xmethods.py b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
index 71a5b75..eb0dd79 100644
--- a/libstdc++-v3/python/libstdcxx/v6/xmethods.py
+++ b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
@@ -165,7 +165,7 @@ class ArrayMethodsMatcher(gdb.xmethod.XMethodMatcher):
 class DequeWorkerBase(gdb.xmethod.XMethodWorker):
 def __init__(self, val_type):
 self._val_type = val_type
-self._bufsize = int(512 / val_type.sizeof) or 1
+self._bufsize = 512 // val_type.sizeof or 1
 
 def size(self, obj):
 first_node = obj['_M_impl']['_M_start']['_M_node']
@@ -176,7 +176,7 @@ class DequeWorkerBase(gdb.xmethod.XMethodWorker):
 
 def index(self, obj, idx):
 first_node = obj['_M_impl']['_M_start']['_M_node']
-index_node = first_node + int(idx / self._bufsize)
+index_node = first_node + int(idx) // self._bufsize
 return index_node[0][idx % self._bufsize]
 
 class DequeEmptyWorker(DequeWorkerBase):
@@ -419,7 +419,7 @@ class VectorWorkerBase(gdb.xmethod.XMethodWorker):
 if self._val_type.code == gdb.TYPE_CODE_BOOL:
 start = obj['_M_impl']['_M_start']['_M_p']
 bit_size = start.dereference().type.sizeof * 8
-valp = start + int(index / bit_size)
+valp = start + index // bit_size
 offset = index % bit_size
 return (valp.dereference() & (1 << offset)) > 0
 else:

Re: [PATCH] libstdc++/77645 fix deque and vector xmethods for Python 3

[Jonathan Wakely]

On 19/09/16 21:39 +, Joseph Myers wrote:

On Mon, 19 Sep 2016, Jonathan Wakely wrote:


On 19/09/16 17:24 +, Joe Buck wrote:
> Python has a distinct integer division operator, "//".  7 // 3 returns the
> integer 2.

Python 3 does, but Python 2 doesn't have it unless you import it from
__future, and I don't know how far back that works. I don't want to
introduce a fix for Python 3 that breaks it for old systems.


No, // is available in Python, without needing __future__, from 2.2
onwards.


I stand corrected, thanks both of you.

I'll test and commnit this then.


commit 07345154582af68b50866cbe9b90432f2d45
Author: Jonathan Wakely 
Date:   Tue Sep 20 09:38:49 2016 +0100

Use python floored quotient operator in xmethods

	* python/libstdcxx/v6/xmethods.py (DequeWorkerBase.__init__)
	(DequeWorkerBase.index, VectorWorkerBase.get): Use // for division.

diff --git a/libstdc++-v3/python/libstdcxx/v6/xmethods.py b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
index 71a5b75..ed6a111 100644
--- a/libstdc++-v3/python/libstdcxx/v6/xmethods.py
+++ b/libstdc++-v3/python/libstdcxx/v6/xmethods.py
@@ -165,7 +165,7 @@ class ArrayMethodsMatcher(gdb.xmethod.XMethodMatcher):
 class DequeWorkerBase(gdb.xmethod.XMethodWorker):
 def __init__(self, val_type):
 self._val_type = val_type
-self._bufsize = int(512 / val_type.sizeof) or 1
+self._bufsize = 512 // val_type.sizeof or 1
 
 def size(self, obj):
 first_node = obj['_M_impl']['_M_start']['_M_node']
@@ -176,7 +176,7 @@ class DequeWorkerBase(gdb.xmethod.XMethodWorker):
 
 def index(self, obj, idx):
 first_node = obj['_M_impl']['_M_start']['_M_node']
-index_node = first_node + int(idx / self._bufsize)
+index_node = first_node + idx // self._bufsize
 return index_node[0][idx % self._bufsize]
 
 class DequeEmptyWorker(DequeWorkerBase):
@@ -419,7 +419,7 @@ class VectorWorkerBase(gdb.xmethod.XMethodWorker):
 if self._val_type.code == gdb.TYPE_CODE_BOOL:
 start = obj['_M_impl']['_M_start']['_M_p']
 bit_size = start.dereference().type.sizeof * 8
-valp = start + int(index / bit_size)
+valp = start + index // bit_size
 offset = index % bit_size
 return (valp.dereference() & (1 << offset)) > 0
 else:

Re: [PATCH] libstdc++/77645 fix deque and vector xmethods for Python 3

[Joseph Myers]

On Mon, 19 Sep 2016, Jonathan Wakely wrote:

> On 19/09/16 17:24 +, Joe Buck wrote:
> > Python has a distinct integer division operator, "//".  7 // 3 returns the
> > integer 2.
> 
> Python 3 does, but Python 2 doesn't have it unless you import it from
> __future, and I don't know how far back that works. I don't want to
> introduce a fix for Python 3 that breaks it for old systems.

No, // is available in Python, without needing __future__, from 2.2 
onwards.

-- 
Joseph S. Myers
jos...@codesourcery.com

Re: [PATCH] libstdc++/77645 fix deque and vector xmethods for Python 3

[Jonathan Wakely]

On 19/09/16 17:24 +, Joe Buck wrote:

Python has a distinct integer division operator, "//".  7 // 3 returns the 
integer 2.


Python 3 does, but Python 2 doesn't have it unless you import it from
__future, and I don't know how far back that works. I don't want to
introduce a fix for Python 3 that breaks it for old systems.

Using a cast is clear and (AFAIK) works with all versions.

RE: [PATCH] libstdc++/77645 fix deque and vector xmethods for Python 3

[Joe Buck]

Python has a distinct integer division operator, "//".  7 // 3 returns the 
integer 2.

-Original Message-
From: libstdc++-ow...@gcc.gnu.org [mailto:libstdc++-ow...@gcc.gnu.org] On 
Behalf Of Jonathan Wakely
Sent: Monday, September 19, 2016 10:11 AM
To: libstd...@gcc.gnu.org; gcc-patches@gcc.gnu.org
Subject: [PATCH] libstdc++/77645 fix deque and vector xmethods for Python 3

The problem for these xmethods is that in Python 3 division of two integers 
produces a float, and GDB then doesn't allow that value to be used for pointer 
arithmetic (https://sourceware.org/PR20622).

PR libstdc++/77645
* python/libstdcxx/v6/xmethods.py (DequeWorkerBase.__init__)
(DequeWorkerBase.index, VectorWorkerBase.get): Cast results of
division to int to work with Python 3.

Tested x86_64-linux, committed to trunk.

I'll fix it for gcc-5 and gcc-6 too.