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• Can I ignore a SIGFPE resulting from division by zero?

  - by Mikeage

  I have a program which deliberately performs a divide by zero (and stores the result in a volatile variable) in order to halt in certain circumstances. However, I'd like to be able to disable this halting, without changing the macro that performs the division by zero. Is there any way to ignore it? I've tried using #include <signal.h> ... int main(void) { signal(SIGFPE, SIG_IGN); ... } but it still dies with the message "Floating point exception (core dumped)". I don't actually use the value, so I don't really care what's assigned to the variable; 0, random, undefined... EDIT: I know this is not the most portable, but it's intended for an embedded device which runs on many different OSes. The default halt action is to divide by zero; other platforms require different tricks to force a watchdog induced reboot (such as an infinite loop with interrupts disabled). For a PC (linux) test environment, I wanted to disable the halt on division by zero without relying on things like assert.

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• jQuery .attr() crashing Internet Explorer

  - by Sunyatasattva

  Hello everyone, This is my first time posting a question here, as I usually try to find solutions myself. This one, though, being an IE issue, just drives me crazy. I use jQuery cycle plug-in on a website I made and, to populate a caption div, I use a little function that is called after the image is loaded, which uses the "alt" attribute of the image. This seems to exasperate Internet Explorer, which, doesn't have the time to fulfill this apparently so-complicated task, and, as the slideshow cycles, it enters in an infinite loop and eventually crashes – the newer the version, the worse the crash: the older IEs just display an error message saying “The webpage cannot be displayed”, while the newer (7 and 8) completely crash the system. I have no idea on how to solve or work around this. Here is the problematic code. function changeCaption() { var caption = $("img", this).attr("alt"); $('#caption').fadeIn("slow").html(caption); } Thanks in advance for any pointer: I am amazed as how something so simple and globally recognized (didn't encounter any other browser who had problem with this), can cause a problem so big. I also read somewhere that being able to crash a browser remotely is a serious issue :) Lucio

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• python 'with' statement

  - by Stephen

  Hi, I'm using Python 2.5. I'm trying to use this 'with' statement. from __future__ import with_statement a = [] with open('exampletxt.txt','r') as f: while True: a.append(f.next().strip().split()) print a The contents of 'exampletxt.txt' are simple: a b In this case, I get the error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/tmp/python-7036sVf.py", line 5, in <module> a.append(f.next().strip().split()) StopIteration And if I replace f.next() with f.read(), it seems to be caught in an infinite loop. I wonder if I have to write a decorator class that accepts the iterator object as an argument, and define an __exit__ method for it? I know it's more pythonic to use a for-loop for iterators, but I wanted to implement a while loop within a generator that's called by a for-loop... something like def g(f): while True: x = f.next() if test(x): a = x elif test(x): b = f.next() yield [a,x,b] a = [] with open(filename) as f: for x in g(f): a.append(x)

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• Switch statement usage - C

  - by Jamie Keeling

  Hello, I have a thread function on Process B that contains a switch to perform certain operations based on the results of an event sent from Process A, these are stored as two elements in an array. I set the first element to the event which signals when Process A has data to send and I have the second element set to the event which indicates when Process A has closed. I have began to implement the functionality for the switch statement but I'm not getting the results as I expect. Consider the following: // //Thread function DWORD WINAPI ThreadFunc(LPVOID passedHandle) { for(i = 0; i < 2; i++) { ghEvents[i] = OpenEvent(EVENT_ALL_ACCESS, FALSE, TEXT("Global\\ProducerEvents")); if(ghEvents[i] == NULL) { getlasterror = GetLastError(); } } dwProducerEventResult = WaitForMultipleObjects( 2, ghEvents, FALSE, INFINITE); switch (dwProducerEventResult) { case WAIT_OBJECT_0 + 0: { //Producer sent data //unpackedHandle = *((HWND*)passedHandle); MessageBox(NULL,L"Test",L"Test",MB_OK); break; } case WAIT_OBJECT_0 + 1: { //Producer closed ExitProcess(1); break; } default: return; } } As you can see if the event in the first array is signalled Process B should display a simple message box, if the second array is signalled the application should close. When I actually close Process A, Process B displays the message box instead. If I leave the first case blank (Do nothing) both applications close as they should. Furthermore Process B sends data an error is thrown (When I comment out the unpacking): Have I implemented my switch statement incorrectly? I though I handled the unpacking of the HWND correctly too, any suggestions? Thanks for your time.

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• How close can I get C# to the performance of C++ for small intensive tasks?

  - by SLC

  I was thinking about the speed difference of C++ to C# being mostly about C# compiling to byte-code that is taken in by the JIT compiler (is that correct?) and all the checks C# does. I notice that it is possible to turn a lot of these functions off, both in the compile options, and possibly through using the unsafe keyword as unsafe code is not verifiable by the common language runtime. Therefore if you were to write a simple console application in both languages, that flipped an imaginary coin an infinite number of times and displayed the results to the screen every 10,000 or so iterations, how much speed difference would there be? I chose this because it's a very simple program. I'd like to test this but I don't know C++ or have the tools to compile it. This is my C# version though: static void Main(string[] args) { unsafe { Random rnd = new Random(); int heads = 0, tails = 0; while (true) { if (rnd.NextDouble() > 0.5) heads++; else tails++; if ((heads + tails) % 1000000 == 0) Console.WriteLine("Heads: {0} Tails: {1}", heads, tails); } } } Is the difference enough to warrant deliberately compiling sections of code "unsafe" or into DLLs that do not have some of the compile options like overflow checking enabled? Or does it go the other way, where it would be beneficial to compile sections in C++? I'm sure interop speed comes into play too then. To avoid subjectivity, I reiterate the specific parts of this question as: Does C# have a performance boost from using unsafe code? Do the compile options such as disabling overflow checking boost performance, and do they affect unsafe code? Would the program above be faster in C++ or negligably different? Is it worth compiling long intensive number-crunching tasks in a language such as C++ or using /unsafe for a bonus? Less subjectively, could I complete an intensive operation faster by doing this?

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• Treetop basic parsing and regular expression usage

  - by ucint

  I'm developing a script using the ruby Treetop library and having issues working with its syntax for regex's. First off, many regular expressions that work in other settings dont work the same in treetop. This is my grammar: (myline.treetop) grammar MyLine rule line string whitespace condition end rule string [\S]* end rule whitespace [\s]* end rule condition "new" / "old" / "used" end end This is my usage: (usage.rb) require 'rubygems' require 'treetop' require 'polyglot' require 'myline' parser = MyLineParser.new p parser.parse("randomstring new") This should find the word new for sure and it does! Now I wont to extend it so that it can find new if the input string becomes "randomstring anotherstring new yetanother andanother" and possibly have any number of strings followed by whitespace (tab included) before and after the regex for rule condition. In other words, if I pass it any sentence with the word "new" etc in it, it should be able to match it. So let's say I change my grammar to: rule line string whitespace condition whitespace string end Then, it should be able to find a match for: p parser.parse("randomstring new anotherstring") So, what do I have to do to allow the string whitespace to be repeated before and after condition? If I try to write this: rule line (string whitespace)* condition (whitespace string)* end , it goes in an infinite loop. If i replace the above () with [], it returns nil In general, regex's return a match when i use the above, but treetop regex's dont. Does anyone have any tips/points on how to go about this? Plus, since there isn't much documentation for treetop and the examples are either too trivial or too complex, is there anyone who knows a more thorough documentation/guide for treetop?

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• Is it possible to unstick a remote IIS ASP server after an exception hangs the session?

  - by user89691

  I have been coding an app in classic ASP that accesses 2 Access databases. I had a page I was working on throw an exception, which is normal during development and causes no lasting problems. This time however, after the exception any attempt to open either of the databases would freeze the session with an infinite script timeout. If I delete the session cookie I an able to access ASP pages again until I try to open the database again. The database that was open when the exception was thrown is left open. There is a LDB lock file and I can't rename or delete either the LDB or MDB file, though I can download the MDB file with FTP. The 2nd access database is not open but any attempt to read this also hangs the session. Accessing HTML pages is fine. The site is hosted with Hostway and they are not interested ("Coding problem = Your problem" even though it leaves my site dead in the water, I suspect until the next reboot, whenever that might be). Here is the dump from the relevant ASP page that threw the exception: Active Server Pages error 'ASP 0115' Unexpected error /translatestats.asp A trappable error (C0000005) occurred in an external object. The script cannot continue running. Active Server Pages error 'ASP 0240' Script Engine Exception /translatestats.asp A ScriptEngine threw exception 'C0000005' in 'IActiveScript::Close()' from 'CActiveScriptEngine::FinalRelease()'. Is there any way I can unstick the site / force close the database remotely ?

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• Multi-level shop, xml or sql. best practice?

  - by danrichardson

  Hello, i have a general "best practice" question regarding building a multi-level shop, which i hope doesn't get marked down/deleted as i personally think it's quite a good "subjective" question. I am a developer in charge (in most part) of maintaining and evolving a cms system and associated front-end functionality. Over the past half year i have developed a multiple level shop system so that an infinite level of categories may exist down into a product level and all works fine. However over the last week or so i have questioned by own methods in front-end development and the best way to show the multi-level data structure. I currently use a sql server database (2000) and pull out all the shop levels and then process them into an enumerable typed list with child enumerable typed lists, so that all levels are sorted. This in my head seems quite process heavy, but we're not talking about thousands of rows, generally only 1-500 rows maybe. I have been toying with the idea recently of storing the structure in an XML document (as well as the database) and then sending last modified headers when serving/requesting the document for, which would then be processed as/when nessecary with an xsl(t) document - which would be processed server side. This is quite a handy, reusable method of storing the data but does it have more overheads in the fact im opening and closing files? And also the xml will require a bit of processing to pull out blocks of xml if for instance i wanted to show two level mid way through the tree for a side menu. I use the above method for sitemap purposes so there is currently already code i have built which does what i require, but unsure what the best process is to go about. Maybe a hybrid method which pulls out the data, sorts it and then makes an xml document/stream (XDocument/XmlDocument) for xsl processing is a good way? - This is the way i currently make the cms work for the shop. So really (and thanks for sticking with me on this), i am just wandering which methods other people use or recommend as being the best/most logical way of doing things. Thanks Dan

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• Check if files in a directory are still being written using Windows Batch Script

  - by FMFF

  Hello. Here's my batch file to parse a directory, and zip files of certain type REM Begin ------------------------ tasklist /FI "IMAGENAME eq 7za.exe" /FO CSV > search.log FOR /F %%A IN (search.log) DO IF %%~zA EQU 0 GOTO end for /f "delims=" %%A in ('dir C:\Temp\*.ps /b') do ( "C:\Program Files\7-Zip\cmdline\7za.exe" a -tzip -mx9 "C:\temp\Zip\%%A.zip" "C:\temp\%%A" Move "C:\temp\%%A" "C:\Temp\Archive" ) :end del search.log REM pause exit REM End --------------------------- This code works just fine for 90% of my needs. It will be deployed as a scheduled task. However, the *.ps files are rather large (minimum of 1GB) in real time cases. So the code is supposed to check if the incoming file is completely written and is not locked by the application that is writing it. I saw another example elsewhere, that suggested the following approach :TestFile ren c:\file.txt c:\file.txt if errorlevel 0 goto docopy sleep 5 goto TestFile :docopy However this example is good for a fixed file. How can I use that many labels and GoTo's inside a for loop without causing an infinite loop? Or is this code safe to be used in the For Loop? Thank you for any help.

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• How can I make a Maybe-Transformer MaybeT into an instance of MonadWriter?

  - by martingw

  I am trying to build a MaybeT-Transformer Monad, based on the example in the Real World Haskell, Chapter Monad Transformers: data MaybeT m a = MaybeT { runMT :: m (Maybe a) } instance (Monad m) => Monad (MaybeT m) where m >>= f = MaybeT $ do a <- runMT m case a of Just x -> runMT (f x) Nothing -> return Nothing return a = MaybeT $ return (Just a) instance MonadTrans MaybeT where lift m = MaybeT $ do a <- m return (Just a) This works fine, but now I want to make MaybeT an instance of MonadWriter: instance (MonadWriter w m) => MonadWriter w (MaybeT m) where tell = lift . tell listen m = MaybeT $ do unwrapped <- listen (runMT m) return (Just unwrapped) The tell is ok, but I can't get the listen function right. The best I could come up with after 1 1/2 days of constructor origami is the one you see above: unwrapped is supposed to be a tuple of (Maybe a, w), and that I want to wrap up in a Maybe-Type and put the whole thing in an empty MonadWriter. But the compiler complains with: Occurs check: cannot construct the infinite type: a = Maybe a When generalising the type(s) for `listen' In the instance declaration for `MonadWriter w (MaybeT m)' What am I missing?

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• Time Machine for Windows?

  - by Blub

  Finally got convinced to start using some kind of version control for my code instead of zipping down a copy of the project at the end of each day. Downloaded Tortoise SVN and used it to create a repository localy on my hdd. I've been using it for 2 days now but I have to say that using it is actually more hassle than just copying the project manually in explorer. Sure, you only store incremental changes but with the cheap disks of today I can't really say that's an argument when you only have small projects. I haven't realy found a quick way to browse the older versions of my files eighter. What I want is an infinite undo that is completely transparent while I code, if I save the file I want a backup. I don't want to check out, check in and don't even get me started on moving files. I haven't tried Time Machine for OS X but it looks like it's exactly what I'm looking for. Does such a program exist for windows? Preferably free and with some kind of tagging-system so I can tag a timestamp when the project is working etc. Maybe should add that I mostly work alone on a single computer. Update: Some of you asked why I want backup. Since I work alone it's mostly to allow me to quickly hack up a solution without worrying that something will screw up.

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• ASP.NET: disabling authentication for a single aspx page (custom error page)?

  - by Richard Collette

  I am using a custom error page: <customErrors redirectMode="ResponseRedirect" mode="On" defaultRedirect="Error2.aspx"/> I want to disable authentication for the custom error page because the error being raised is related to an authentication module and I don't want to get into an infinite loop and I want to display a clean error page to the user. I have been trying the following configuration to do that. <location path="Error2.aspx"> <system.web> <authentication mode="None"/> <authorization> <allow users="?"/> <allow users="*"/> </authorization> </system.web> </location> I am getting a System.Configuration.ConfigurationErrorsException for the line that sets the authentication mode. It is an error to use a section registered as allowDefinition='MachineToApplication' beyond application level. This error can be caused by a virtual directory not being configured as an application in IIS. I have verified that there are no other web.config files in subdirectories under the application's folder. The applications folder is configured as an application in IIS and the error page is at the application's root. File permissions set for the error page in IIS include anonymous and windows authentication (I have tried just anonymous as well).

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• Throttling CPU/Memory usage of a Thread in Java?

  - by Nalandial

  I'm writing an application that will have multiple threads running, and want to throttle the CPU/memory usage of those threads. There is a similar question for C++, but I want to try and avoid using C++ and JNI if possible. I realize this might not be possible using a higher level language, but I'm curious to see if anyone has any ideas. EDIT: Added a bounty; I'd like some really good, well thought out ideas on this. EDIT 2: The situation I need this for is executing other people's code on my server. Basically it is completely arbitrary code, with the only guarantee being that there will be a main method on the class file. Currently, multiple completely disparate classes, which are loaded in at runtime, are executing concurrently as separate threads. I inherited this code (the original author is gone). The way it's written, it would be a pain to refactor to create separate processes for each class that gets executed. If that's the only good way to limit memory usage via the VM arguments, then so be it. But I'd like to know if there's a way to do it with threads. Even as a separate process, I'd like to be able to somehow limit its CPU usage, since as I mentioned earlier, several of these will be executing at once. I don't want an infinite loop to hog up all the resources. EDIT 3: An easy way to approximate object size is with java's Instrumentation classes; specifically, the getObjectSize method. Note that there is some special setup needed to use this tool.

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• Qt - QWebView Problem

  - by user547057

  Hi, I have a PyQt gui script which consists of a QWebView widget. I'm trying to send a GET request, i.e go to a page, fill a form and hit click using the code at the bottom of this question. Since i'm dealing with the documentElement(a QWebElement) of the webview, I need to place all DOM actions in a separate function(which I have named fillForm) and connect the loadFinished() signal into the function. Without connecting the signal, the document will not have loaded and I won't be able to get the elements I want. I'm able to submit the form correctly and get the proper response from the webpage. The problem i'm having is that, the above leads to a sort of infinite loop. This is because the webpage gets reloaded each time a new page is loaded, so the form gets filled each and every single time without stopping. I'd like to know if there's some way of finding out whether the WebView's page has loaded fully, non-asynchronously or maybe pause execution of the script(without freezing the gui) until the whole document has loaded. I'm unable to come up with a satisfactory solution(my idea consisted of keeping a global variable to track clicks) to this problem. I would appreciate it if someone could help me out with a better way to tackle this. Thanks! Here's the code i'm using import sys from PyQt4.QtCore import * from PyQt4.QtGui import * from PyQt4.QtWebKit import * from PyQt4 import QtCore app = QApplication(sys.argv) web = QWebView() web.load(QUrl("http://mywebsite.com")) def fillForm(): doc = web.page().mainFrame().documentElement() searchform = doc.findFirst("input[type=text]") searchform.setAttribute("value", "hello") button = doc.findFirst("input[type=submit]") button.evaluateJavaScript("click()") QtCore.QObject.connect(web, QtCore.SIGNAL("loadFinished"), fillForm) web.show() sys.exit(app.exec_())

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• Why doesn't gcc remove this check of a non-volatile variable?

  - by Thomas

  This question is mostly academic. I ask out of curiosity, not because this poses an actual problem for me. Consider the following incorrect C program. #include <signal.h> #include <stdio.h> static int running = 1; void handler(int u) { running = 0; } int main() { signal(SIGTERM, handler); while (running) ; printf("Bye!\n"); return 0; } This program is incorrect because the handler interrupts the program flow, so running can be modified at any time and should therefore be declared volatile. But let's say the programmer forgot that. gcc 4.3.3, with the -O3 flag, compiles the loop body (after one initial check of the running flag) down to the infinite loop .L7: jmp .L7 which was to be expected. Now we put something trivial inside the while loop, like: while (running) putchar('.'); And suddenly, gcc does not optimize the loop condition anymore! The loop body's assembly now looks like this (again at -O3): .L7: movq stdout(%rip), %rsi movl $46, %edi call _IO_putc movl running(%rip), %eax testl %eax, %eax jne .L7 We see that running is re-loaded from memory each time through the loop; it is not even cached in a register. Apparently gcc now thinks that the value of running could have changed. So why does gcc suddenly decide that it needs to re-check the value of running in this case?

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• A really smart rails helper needed

  - by Stefan Liebenberg

  In my rails application I have a helper function: def render_page( permalink ) page = Page.find_by_permalink( permalink ) content_tag( :h3, page.title ) + inline_render( page.body ) end If I called the page "home" with: <%= render_page :home %> and "home" page's body was: <h1>Home<h1/> bla bla <%= render_page :about %> <%= render_page :contact %> I would get "home" page, with "about" and "contact", it's nice and simple... right up to where someone goes and changes the "home" page's content to: <h1>Home<h1/> bla bla <%= render_page :home %> <%= render_page :about %> <%= render_page :contact %> which will result in a infinite loop ( a segment fault on webrick )... How would I change the helper function to something that won't fall into this trap? My first attempt was along the lines of: @@list = [] def render_page( permalink ) unless list.include?(permalink) @@list += [ permalink ] page = Page.find_by_permalink content_tag( :h3, page.title ) + inline_render( page.body ) @@list -= [ permalink ] else content_tag :b, "this page is already being rendered" end end which worked on my development environment, but bombed out in production... any suggestions? Thank You Stefan

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• Recursion Problems in Prolog

  - by Humble_Student

  I'm having some difficulties in prolog, I'm trying to write a predicate that will return all paths between two cities, although at the moment it returns the first path it finds on an infinite loop. Not sure where I'm going wrong but I've been trying to figure this out all day and I'm getting nowhere. Any help that could be offered would be appreciated. go:- repeat, f([],0,lon,spa,OP,OD), write(OP), write(OD), fail. city(lon). city(ath). city(spa). city(kol). path(lon,1,ath). path(ath,3,spa). path(spa,2,kol). path(lon,1,kol). joined(X,Y,D):- path(X,D,Y);path(Y,D,X). f(Ci_Vi,Di,De,De,PaO,Di):- append([De],Ci_Vi,PaO), !. f(Cities_Visited,Distance,Start,Destination,Output_Path,Output_Distance):- repeat, city(X), joined(Start,X,D), not_member(X,Cities_Visited), New_Distance is Distance + D, f([Start|Cities_Visited],New_Distance,X,Destination,Output_Path,Output_Distance). not_member(X,List):- member(X,List), !, fail. not_member(X,List). The output I'm expecting here is [spa,ath,lon]4 [spa,kol,lon]3. Once again, any help would be appreciated. Many thanks in advance.

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• Lightweight alternative to Manual/AutoResetEvent in C#

  - by sweetlilmre

  Hi, I have written what I hope is a lightweight alternative to using the ManualResetEvent and AutoResetEvent classes in C#/.NET. The reasoning behind this was to have Event like functionality without the weight of using a kernel locking object. Although the code seems to work well in both testing and production, getting this kind of thing right for all possibilities can be a fraught undertaking and I would humbly request any constructive comments and or criticism from the StackOverflow crowd on this. Hopefully (after review) this will be useful to others. Usage should be similar to the Manual/AutoResetEvent classes with Notify() used for Set(). Here goes: using System; using System.Threading; public class Signal { private readonly object _lock = new object(); private readonly bool _autoResetSignal; private bool _notified; public Signal() : this(false, false) { } public Signal(bool initialState, bool autoReset) { _autoResetSignal = autoReset; _notified = initialState; } public virtual void Notify() { lock (_lock) { // first time? if (!_notified) { // set the flag _notified = true; // unblock a thread which is waiting on this signal Monitor.Pulse(_lock); } } } public void Wait() { Wait(Timeout.Infinite); } public virtual bool Wait(int milliseconds) { lock (_lock) { bool ret = true; // this check needs to be inside the lock otherwise you can get nailed // with a race condition where the notify thread sets the flag AFTER // the waiting thread has checked it and acquires the lock and does the // pulse before the Monitor.Wait below - when this happens the caller // will wait forever as he "just missed" the only pulse which is ever // going to happen if (!_notified) { ret = Monitor.Wait(_lock, milliseconds); } if (_autoResetSignal) { _notified = false; } return (ret); } } }

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• Our Flash Streaming Player Occasionally Stutters like a Skipping CD after a Period of Time

  - by Jonathan Fritz

  We offer a streaming player for a number of our clients, who are responsible for their providing us with their own audio streams. We have written a very simple flash player that can play all of the streams that we support (icecast/shoutcast/live365/mp3 over http/etc). Unfortunately, we have found that when listening, our player sometimes begins to stutter (like a skipping cd), sometimes after only 10 minutes, and sometimes after an hour of listening. We have noticed this behaviour in firefox on both linux and windows. Does anybody know anything about this problem? We know that flash isn't ideal for infinite streams of audio, but it's about all that we can find that's on every platform out there. If anybody can suggest a solution to our problem, I'll be your friend forever. Here is a link to the live player: http://cr-jf.jfritz.02.dev.wecreate.com/streaming/player_v5/ Note that you'll need to test in a browser that isn't IE, because we use WMP in IE, and that the JavaScript on the page will cause the player to unload and re-load once an hour because of memory issues. Because I can only put one hyperlink in a post, I'll add a link to the player source code as a comment. Thanks all!

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• Using GCC (MinGW) to compile OpenGL on Windows

  - by Casey

  I've searched on google and haven't been able to come up with a solution. I would like to compile some OpenGL programming using GCC. In the GL folder in GCC I have the following headers: gl.h glext.h glu.h Then in my system32 file I have the following .dll opengl32.dll glu32.dll glut32.dll If I wanted to write a simple OpenGL "Hello World" and link and compile with GCC, what is the correct process? I'm attempting to use this code: #include <GL/gl.h> #include <GL/glut.h> void display() { glClear(GL_COLOR_BUFFER_BIT); glFlush(); } int main(int argc, char **argv) { glutInit(&argc, argv); glutInitWindowSize(512,512); glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB); glutCreateWindow("The glut hello world program"); glutDisplayFunc(display); glClearColor(0.0, 0.0, 0.0, 1.0); glutMainLoop(); // Infinite event loop return 0; } Thank you in advance for the help.

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• Use of Syntactic Sugar / Built in Functionality

  - by Kyle Rozendo

  I was busy looking deeper into things like multi-threading and deadlocking etc. The book is aimed at both pseudo-code and C code and I was busy looking at implementations for things such as Mutex locks and Monitors. This brought to mind the following; in C# and in fact .NET we have a lot of syntactic sugar for doing things. For instance (.NET 3.5): lock(obj) { body } Is identical to: var temp = obj; Monitor.Enter(temp); try { body } finally { Monitor.Exit(temp); } There are other examples of course, such as the using() {} construct etc. My question is when is it more applicable to "go it alone" and literally code things oneself than to use the "syntactic sugar" in the language? Should one ever use their own ways rather than those of people who are more experienced in the language you're coding in? I recall having to not use a Process object in a using block to help with some multi-threaded issues and infinite looping before. I still feel dirty for not having the using construct in there. Thanks, Kyle

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• Does SetFileBandwidthReservation affect memory-mapped file performance?

  - by Ghostrider

  Does this function affect Memory-mapped file performance? Here's the problem I need to solve: I have two applications competing for disk access: "reader" and "updater". Whole system runs on Windows Server 2008 R2 x64 "Updater" constantly accesses disk in a linear manner, updating data. They system is set up in such a way that updater always has infinite data to update. Consider that it is constantly approximating a solution of a huge set of equations that takes up entire 2TB disk drive. Updater uses ReadFile and WriteFile to process data in a linear fashion. "Reader" is occasionally invoked by user to get some pieces of data. Usually user would read several 4kb blocks from the drive and stop. Occasionally user needs to read up to 100mb sequentially. In exceptional cases up to several gigabytes. Reader maps files to memory to get data it needs. What I would like to achieve is for "reader" to have absolute priority so that "updater" would completely stop if needed so that "reader" could get the data user needs ASAP. Is this problem solvable by using SetPriorityClass and SetFileBandwidthReservation calls? I would really hate to put synchronization login in "reader" and "updater" and rather have the OS take care of priorities.

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• How to functionally generate a tree breadth-first. (With Haskell)

  - by Dennetik

  Say I have the following Haskell tree type, where "State" is a simple wrapper: data Tree a = Branch (State a) [Tree a] | Leaf (State a) deriving (Eq, Show) I also have a function "expand :: Tree a - Tree a" which takes a leaf node, and expands it into a branch, or takes a branch and returns it unaltered. This tree type represents an N-ary search-tree. Searching depth-first is a waste, as the search-space is obviously infinite, as I can easily keep on expanding the search-space with the use of expand on all the tree's leaf nodes, and the chances of accidentally missing the goal-state is huge... thus the only solution is a breadth-first search, implemented pretty decent over here, which will find the solution if it's there. What I want to generate, though, is the tree traversed up to finding the solution. This is a problem because I only know how to do this depth-first, which could be done by simply called the "expand" function again and again upon the first child node... until a goal-state is found. (This would really not generate anything other then a really uncomfortable list.) Could anyone give me any hints on how to do this (or an entire algorithm), or a verdict on whether or not it's possible with a decent complexity? (Or any sources on this, because I found rather few.)

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• OpenGL Calls Lock/Freeze

  - by Necrolis

  I am using some dell workstations(running WinXP Pro SP 2 & DeepFreeze) for development, but something was recenlty loaded onto these machines that prevents any opengl call(the call locks) from completing(and I know the code works as I have tested it on 'clean' machines, I also tested with simple opengl apps generated by dev-cpp, which will also lock on the dell machines). I have tried to debug my own apps to see where exactly the gl calls freeze, but there is some global system hook on ZwQueryInformationProcess that messes up calls to ZwQueryInformationThread(used by ExitThread), preventing me from debugging at all(it causes the debugger, OllyDBG, to go into an access violation reporting loop or the program to crash if the exception is passed along). the hook: ntdll.ZwQueryInformationProcess 7C90D7E0 B8 9A000000 MOV EAX,9A 7C90D7E5 BA 0003FE7F MOV EDX,7FFE0300 7C90D7EA FF12 CALL DWORD PTR DS:[EDX] 7C90D7EC - E9 0F28448D JMP 09D50000 7C90D7F1 9B WAIT 7C90D7F2 0000 ADD BYTE PTR DS:[EAX],AL 7C90D7F4 00BA 0003FE7F ADD BYTE PTR DS:[EDX+7FFE0300],BH 7C90D7FA FF12 CALL DWORD PTR DS:[EDX] 7C90D7FC C2 1400 RETN 14 7C90D7FF 90 NOP ntdll.ZwQueryInformationToken 7C90D800 B8 9C000000 MOV EAX,9C the messed up function + call: ntdll.ZwQueryInformationThread 7C90D7F0 8D9B 000000BA LEA EBX,DWORD PTR DS:[EBX+BA000000] 7C90D7F6 0003 ADD BYTE PTR DS:[EBX],AL 7C90D7F8 FE ??? ; Unknown command 7C90D7F9 7F FF JG SHORT ntdll.7C90D7FA 7C90D7FB 12C2 ADC AL,DL 7C90D7FD 14 00 ADC AL,0 7C90D7FF 90 NOP ntdll.ZwQueryInformationToken 7C90D800 B8 9C000000 MOV EAX,9C So firstly, anyone know what if anything would lead to OpenGL calls cause an infinite lock,and if there are any ways around it? and what would be creating such a hook in kernal memory ? Update: After some more fiddling, I have discovered a few more kernal hooks, a lot of them are used to nullify data returned by system information calls(such as the remote debugging port), I also managed to find out the what ever is doing this is using madchook.dll(by madshi) to do this, this dll is also injected into every running process(these seem to be some anti debugging code). Also, on the OpenGL side, it seems Direct X is fine/unaffected(I ran one of the DX 9 demo's without problems), so could one of these kernal hooks somehow affect OpenGL?

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• Perl's Devel::LeakTrace::Fast Pointing to blank files and evals

  - by kt

  I am using Devel::LeakTrace::Fast to debug a memory leak in a perl script designed as a daemon which runs an infinite loop with sleeps until interrupted. I am having some trouble both reading the output and finding documentation to help me understand the output. The perldoc doesn't contain much information on the output. Most of it makes sense, such as pointing to globals in DBI. Intermingled with the output, however, are several leaked SV(<LOCATION>) from (eval #) line # Where the numbers are numbers and <LOCATION> is a location in memory. The script itself is not using eval at any point - I have not investigated each used module to see if evals are present. Mostly what I want to know is how to find these evals (if possible). I also find the following entries repeated over and over again leaked SV(<LOCATION>) from line # Where line # is always the same #. Not very helpful in tracking down what file that line is in.

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