473,834 Members | 1,547 Online
Bytes | Software Development & Data Engineering Community
+ Post

Home Posts Topics Members FAQ

Segv in mmap.move()

Does anyone recognize this little Python crasher?

I'll file a bug report unless someone notices it as an already
documented bug. I found some open mmap bugs, but it wasn't
obvious to me that this problem was one of those...

Python 2.5.2 (r252:60911, Apr 21 2008, 11:12:42)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.
>>import mmap
data = mmap.mmap(-1, 1)
data.move(1,1 ,-1)
Segmenteringsfe l (core dumped)

I first noticed the problem under Windows in 2.5.1.
Jul 23 '08 #1
1 1686


ma**********@gm ail.com wrote:
Does anyone recognize this little Python crasher?

I'll file a bug report unless someone notices it as an already
documented bug. I found some open mmap bugs, but it wasn't
obvious to me that this problem was one of those...

Python 2.5.2 (r252:60911, Apr 21 2008, 11:12:42)
[GCC 4.2.3 (Ubuntu 4.2.3-2ubuntu7)] on linux2
Type "help", "copyright" , "credits" or "license" for more information.
>>>import mmap
data = mmap.mmap(-1, 1)
data.move(1, 1,-1)
Segmenteringsfe l (core dumped)

I first noticed the problem under Windows in 2.5.1.
On WinXP Py3.0b2, I see two bugs here.

1. For a length 1 sequence, the only offsets allowed should be 0.
However, I can index to what I suspect is a null terminator byte at
offset len(seq). This should be internally accessible only just as for
regular strings and bytes (which also have null terminators, I believe).
Indexing any farther past what should be the end gives the IndexError
I expected when indexing just past the end. (Slicing and iterating,
however, work correctly.)
>>import mmap
d=mmap.mmap (-1,5)
>>d[:]=b'abcde'
d[0], d[4],d[5]
(97, 101, 0)

2. Running your code, or d.move(1,2,-1), I get python.exe 'encountered a
problem ...shutting down ... Send report?' (yes) and window closed.
Running IDLE, same msg, but after send report, IDLE shell restarted. Cute.

Modules/mmapmodule.c - mmap_move_metho d declares count as unsigned.
Further experimentation shows that the problem is telling it to move
exactly -1 bytes, which I am sure gets translated to 2**32-1 = 4294967295 by
PyArg_ParseTupl e(args, "kkk:move", &dest, &src, &count)
Passing 2**32-1 also crashes, while 2*32-2 and other bad values give
>>d.move(1,2,2* *32-2)
Traceback (most recent call last):
File "<pyshell#5 1>", line 1, in <module>
d.move(1,2,2**3 2-2)
ValueError: source or destination out of range

I suspect the 2**32-1 bug is in C memmove, perhap inherited from a
common source.

I think either a)the docs should warn that a count of -1== 4294967295
(on 32bit machines) and just that may crash the interpreter or b) the
wrapper of the underlying C function should raise ValueError for -1
also. The goal of 'no crashes' suggests the latter if sensibly possible.

Terry Jan Reedy

Jul 23 '08 #2

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

4
3546
by: Hao Xu | last post by:
Hi everyone! I found that if you want to write to the memory got by mmap(), you have to get the file descriptor for mmap() in O_RDWR mode. If you got the file descriptor in O_WRONLY mode, then writing to the memory got by mmap() will lead to segmentation fault. Anyone knows why? Is this a rule or a bug? What if I just want to write to the file and nothing else?
4
3711
by: Fabiano Sidler | last post by:
Hi folks! I created an mmap object like so: --- snip --- from mmap import mmap,MAP_ANONYMOUS,MAP_PRIVATE fl = file('/dev/zero','rw') mm = mmap(fl.fileno(), 1, MAP_PRIVATE|MAP_ANONYMOUS) --- snap --- Now, when I try to resize mm to 10 byte
26
9343
by: myeates | last post by:
Hi Anyone ever done this? It looks like Python2.4 won't take a length arg Mathew
1
5475
by: James T. Dennis | last post by:
I've been thinking about the Python mmap module quite a bit during the last couple of days. Sadly most of it has just been thinking ... and reading pages from Google searches ... and very little of it as been coding. Mostly it's just academic curiosity (I might be teaching an "overview of programming" class in a few months, and I'd use Python for most of the practical examples to cover a broad range of programming topics, including the...
5
6079
by: rasmidas | last post by:
I have written a file as below: #include<stdio.h> #include<string.h> #include<stdlib.h> int main() { char* items; int i; for(i=0;i<2;i++)
1
2699
by: koara | last post by:
Hello all, i am using the mmap module (python2.4) to access contents of a file. My question regards the relative performance of mmap.seek() vs mmap.tell(). I have a generator that returns stuff from the file, piece by piece. Since other things may happen to the mmap object in between consecutive next() calls (such as another iterator's next()), i have to store the file position before yield and restore it afterwards by means of tell()...
2
4641
by: Neal Becker | last post by:
On linux, I don't understand why: f = open ('/dev/eos', 'rw') m = mmap.mmap(f.fileno(), 1000000, prot=mmap.PROT_READ|mmap.PROT_WRITE, flags=mmap.MAP_SHARED) gives 'permission denied', but this c++ code works: #include <sys/mman.h> #include <fcntl.h>
0
1154
by: Kris Kennaway | last post by:
If I do the following: def mmap_search(f, string): fh = file(f) mm = mmap.mmap(fh.fileno(), 0, mmap.MAP_SHARED, mmap.PROT_READ) return mm.find(string) def mmap_is_in(f, string): fh = file(f)
0
1125
by: Gabriel Genellina | last post by:
En Thu, 29 May 2008 19:17:05 -0300, Kris Kennaway <kris@FreeBSD.org> escribió: Looks like you should define the sq_contains member in mmap_as_sequence, and the type should have the Py_TPFLAGS_HAVE_SEQUENCE_IN flag set (all in mmapmodule.c) -- Gabriel Genellina
0
9796
marktang
by: marktang | last post by:
ONU (Optical Network Unit) is one of the key components for providing high-speed Internet services. Its primary function is to act as an endpoint device located at the user's premises. However, people are often confused as to whether an ONU can Work As a Router. In this blog post, we’ll explore What is ONU, What Is Router, ONU & Router’s main usage, and What is the difference between ONU and Router. Let’s take a closer look ! Part I. Meaning of...
0
9643
by: Hystou | last post by:
Most computers default to English, but sometimes we require a different language, especially when relocating. Forgot to request a specific language before your computer shipped? No problem! You can effortlessly switch the default language on Windows 10 without reinstalling. I'll walk you through it. First, let's disable language synchronization. With a Microsoft account, language settings sync across devices. To prevent any complications,...
0
10504
jinu1996
by: jinu1996 | last post by:
In today's digital age, having a compelling online presence is paramount for businesses aiming to thrive in a competitive landscape. At the heart of this digital strategy lies an intricately woven tapestry of website design and digital marketing. It's not merely about having a website; it's about crafting an immersive digital experience that captivates audiences and drives business growth. The Art of Business Website Design Your website is...
0
9327
agi2029
by: agi2029 | last post by:
Let's talk about the concept of autonomous AI software engineers and no-code agents. These AIs are designed to manage the entire lifecycle of a software development project—planning, coding, testing, and deployment—without human intervention. Imagine an AI that can take a project description, break it down, write the code, debug it, and then launch it, all on its own.... Now, this would greatly impact the work of software developers. The idea...
0
6951
by: conductexam | last post by:
I have .net C# application in which I am extracting data from word file and save it in database particularly. To store word all data as it is I am converting the whole word file firstly in HTML and then checking html paragraph one by one. At the time of converting from word file to html my equations which are in the word document file was convert into image. Globals.ThisAddIn.Application.ActiveDocument.Select();...
0
5624
by: TSSRALBI | last post by:
Hello I'm a network technician in training and I need your help. I am currently learning how to create and manage the different types of VPNs and I have a question about LAN-to-LAN VPNs. The last exercise I practiced was to create a LAN-to-LAN VPN between two Pfsense firewalls, by using IPSEC protocols. I succeeded, with both firewalls in the same network. But I'm wondering if it's possible to do the same thing, with 2 Pfsense firewalls...
0
5790
by: adsilva | last post by:
A Windows Forms form does not have the event Unload, like VB6. What one acts like?
2
3975
muto222
by: muto222 | last post by:
How can i add a mobile payment intergratation into php mysql website.
3
3079
bsmnconsultancy
by: bsmnconsultancy | last post by:
In today's digital era, a well-designed website is crucial for businesses looking to succeed. Whether you're a small business owner or a large corporation in Toronto, having a strong online presence can significantly impact your brand's success. BSMN Consultancy, a leader in Website Development in Toronto offers valuable insights into creating effective websites that not only look great but also perform exceptionally well. In this comprehensive...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.