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  • How do (or can I) hack a gem temporarily while looking for a bug?

    - by Tom Andersen
    I have a gem installed in my home directory on a laptop (eg not THE server). I have installed ruby 1.9.1 and also some other gems, notably right_aws - which allows access to s3, etc with ruby. All works, except there is a bug when I do a query on SimpleDB, and the returned list of items includes an item with any two byte utf-8 character in its itemName(). So I look through the sources of the right_aws gem installed on my machine, and I can see some places where I would like to test a fix. If I edit the file, save changes, (needing a password), then restart the server (script/server), it ignores my changes. I am quite new at ruby - do you have to 'compile' or other similar move to get the source code changes made take effect? I can see the edited file is changed by viewing it in terminal, etc.

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  • Auto not being recognised by the compiler, what would be the best replacement?

    - by user1719605
    So I have wrote a program that uses auto however the compiler doesn't seem to recognize it, probably it is an earlier compiler. I was wondering for my code, with are suitable variables to fix my code so that I do not need to use the auto keyword? I'm thinking a pointer to a string? or a string iterator, though I am not sure. #include <cstdlib> #include <string> #include <iostream> #include <unistd.h> #include <algorithm> using namespace std; int main(int argc, char* argv[]) { enum MODE { WHOLE, PREFIX, SUFFIX, ANYWHERE, EMBEDDED } mode = WHOLE; bool reverse_match = false; int c; while ((c = getopt(argc, argv, ":wpsaev")) != -1) { switch (c) { case 'w': // pattern matches whole word mode = WHOLE; break; case 'p': // pattern matches prefix mode = PREFIX; break; case 'a': // pattern matches anywhere mode = ANYWHERE; break; case 's': // pattern matches suffix mode = SUFFIX; break; case 'e': // pattern matches anywhere mode = EMBEDDED; break; case 'v': // reverse sense of match reverse_match = true; break; } } argc -= optind; argv += optind; string pattern = argv[0]; string word; int matches = 0; while (cin >> word) { switch (mode) { case WHOLE: if (reverse_match) { if (pattern != word) { matches += 1; cout << word << endl; } } else if (pattern == word) { matches += 1; cout << word << endl; } break; case PREFIX: if (pattern.size() <= word.size()) { auto res = mismatch(pattern.begin(), pattern.end(), word.begin()); if (reverse_match) { if (res.first != word.end()) { matches += 1; cout << word << endl; } } else if (res.first == word.end()) { matches += 1; cout << word << endl; } } break; case ANYWHERE: if (reverse_match) { if (!word.find(pattern) != string::npos) { matches += 1; cout << word << endl; } } else if (word.find(pattern) != string::npos) { matches += 1; cout << word << endl; } break; case SUFFIX: if (pattern.size() <= word.size()) { auto res = mismatch(pattern.rbegin(), pattern.rend(), word.rbegin()); if (reverse_match) { if (res.first != word.rend()) { matches = +1; cout << word << endl; } } else if (res.first == word.rend()) { matches = +1; cout << word << endl; } } break; case EMBEDDED: if (reverse_match) { if (!pattern.find(word) != string::npos) { matches += 1; cout << word << endl;} } else if (pattern.find(word) != string::npos) { matches += 1; cout << word << endl; } break; } } return (matches == 0) ? 1 : 0; } Thanks in advance!

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  • Which Firefox add-on is responsible for a rendering bug?

    - by Gilles
    I've found a page that isn't rendered correctly by Firefox with my usual profile. It is rendered correctly with a blank profile. I have quite a few add-ons. One of them is surely the culprit. How can I find out which? Userscripts often affect the rendering. But I turned off Greasemonkey, and it didn't help. So it's something else, presumably an extension (what else could it be? I have no chrome/userChrome.css.). I'm looking for an easy way to find out which one, easier than disabling a bunch of extensions and restarting umpteen times. Related: Create a tool to help users identify a problematic add-on by bisecting the list of installed add-ons — a similar problem which would admit a similar solution. I want to automate this as much as possible; something like git bisect, that doesn't require me to change my actual profile, would be ideal. A Linux-specific solution is fine with me.

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  • Is the recent Java bug something to worry about?

    - by Keith
    Recently saw this announcement on the H blog about a big hole in Java: http://www.h-online.com/security/news/item/Java-exploit-launches-local-Windows-applications-974652.html But I can't seem to get anyone to think it's a big deal. The fact that I cn visit a web site and it runs calc.exe on my local box is just plain scary... Why is there no bigger response to this??

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  • Can I copy a cross compiler tool chain between systems (I did before)?

    - by Jamie
    I tested fairly extensively with Ubuntu 10.04 Beta 2 Server in a VM, and was able to simply copy (read tar x) a cross compiled tool chain from an Ubuntu 8.10 VM. I created the tar myself, which is essentially a lot of stuff in \usr\local. Now that I've got a bare metal installation of Ubuntu 10.04 proper, the copy isn't working. In particularly, I'm getting the error: $ arm-linux-gcc -bash: /usr/local/bin/arm-linux-gcc: No such file or directory I've got the systems side by side in SSH windows ... any suggestions?

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  • Firefox 11.0 Right-Click Dropdown Menu (and Menu Options at Window Top) Flickering - Potential Bug?

    - by nicorellius
    About a week ago my Windows 7 machine starting exhibiting odd Firefox behavior. When I right click on something the drop-down menu flickers and when the mouse is hovering over a field, I can't really see it. This same behavior happens in other ways too, like in the top File, Edit , View, etc menus. I click them and they flicker, when I hover over them, and then they get obscured when I hover over the one I want. I did some research and didn't really find anything. Some people found similar behavior in applications THEY were building. But mine is a global problem. Happens on all sites, as far as I can tell. This is why I suspect it's my Firefox installation. I thought about reinstalling, but if there was another option, I'd like to explore that too. The behavior is not really capture-able, so I don't have anything except words to describe it. Sorry ;-( Thanks.

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  • What data should I (can I) gather to prove a .net bug in third party software?

    - by gef05
    Our users are using a third-party system and every so often - a user might go all day without this happening, other days they may see it two or three times in seven hours - a red x will appear on screen rather than a button, field, or control. This is a .net system. Looking online I can see that this is a .net error. Problem is, our devs didn't write it, and the vendor wants proof that the problem resides with their system, not our PCs. What can we do to gather information on such an issue that would allow us to make our case to the vendor and get them to create a fix? I'm thinking of data to gather - anything from OS, memory. .net version installed etc. But I'd also like to know about error logging - if it's possible to log errors that occur in third-party systems.

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  • what type of bug causes a program to slowly use more processor power and all of a sudden go to 100%?

    - by reinier
    Hi, I was hoping to get some good ideas as to what might be causing a really nasty bug. This is a program which is transmitting data over a socket, and also receives messages back. I could explain lots more, but I don't think this will help here. I'm just searching for hypothetical problems which can cause the following behaviour: program runs processor time slowly accumulates (till around 60%) all of a sudden (could be after 30 but also after 60 seconds) the processor time shoots to 100%. the program halts completely In my syslog it always ends on one line with a memory allocation (something similar to: myArray = new byte[16384]) in the same thread. now here is the weird part: if I set the debugger anywhere...it immediately stops on that line. So just the act of setting a breakpoint, made the thread continue (it wasn't running since I saw no log output anymore) I was thinking 'deadlock' but that would not cause 100% processor power. If anything, the opposite. Also, setting a breakpoint would not cause a deadlock to end. anyone else a theoretical suggestion as to what kind of 'construct' might cause this effect? (apart from 'bad programming') ;^) thanks EDIT: I just noticed.... by setting the sendspeed slower, the problem shows itself much later than expected. I would think around the same amount of packets send...but no the amount of packets send is much higher this way before it has the same problem.

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  • ASP.NET MVC Ajax.BeginForm eats params of submit button clicked. Looks like bug.

    - by RonnBlack
    If you are using Ajax.BeginForm() with multiple submit buttons similar to this: // View.aspx <% using (Ajax.BeginForm("Action", "Controller", new AjaxOptions { UpdateTargetId = "MyControl", })) { %> <span id="MyControl"> <% Html.RenderPartial("MyControl"); %> </span> <% } %> //MyControl.ascx <%@ Control Language="C#" Inherits="System.Web.Mvc.ViewUserControl" %> <input name="prev" type="submit" value="prev" /> <input name="next" type="submit" value="next" /> //... Everything is submitted to the controller fine but the params for the submit button that was clicked are absent from the Request. In otherwords Request["next"] and Request["prev"] are always null. I looked in to the JavaScript in Microsoft.MvcAjax.js and it looks like the function Sys_Mvc_MvcHelpers$_serializeForm completely skips over the inputs that are of type 'submit'. This doesn't seem logical at all. How else can you find out what button has been clicked? It looks like a bug to me. Is there any logical reason to skip these form parameters?

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  • Why can't the compiler/JVM just make autoboxing "just work"?

    - by Pyrolistical
    Autoboxing is rather scary. While I fully understand the difference between == and .equals I can't but help have the follow bug the hell out of me: final List<Integer> foo = Arrays.asList(1, 1000); final List<Integer> bar = Arrays.asList(1, 1000); System.out.println(foo.get(0) == bar.get(0)); System.out.println(foo.get(1) == bar.get(1)); That prints true false Why did they do it this way? It something to do with cached Integers, but if that is the case why don't they just cache all Integers used by the program? Or why doesn't the JVM always auto unbox to primitive? Printing false false or true true would have been way better. EDIT I disagree about breakage of old code. By having foo.get(0) == bar.get(0) return true you already broke the code. Can't this be solved at the compiler level by replacing Integer with int in byte code (as long as it is never assigned null)

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  • Does somebody know something about Flash-CS5' "multiple copies" bug?

    - by Slav
    I'm, generally, complaining, not asking, but if somebody will be able (Adobe isn't) to help - it will be perfect. I use Flash-CS5 IDE to compose .swc files to import it, then, into FlashDevelop. Evetyrhing works fine until SOMETIMES. About each 10th "Ctrl+S" (save) click Flash-CS5 duplicates ALL images (loaded .bmp, .jpg, .png... files) and names them like "Copy ..." where "..." is incrementing number. Furhtermore, Flash-CS5 creates duplications of some layers - other layers have duplications of items which put on them. Restoring project's state to previous (not copied) state - is the hell. This bug is not reproducible but it happens each 2 hours or so - both right after project's opening and after several hours of work. It happens on different machines - I know at least 5 people which told me that they also run into this issue and do not know how to escape it. Did somebody experienced it? Does somebody know how to handle it?

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  • ADO.NET zombie transaction bug? How to ensure that commands will not be executed on implicit transac

    - by TN
    e.g. When deadlock occurs, following SQL commands are successfully executed, even if they have assigned SQL transaction that is after rollback. It seems, it is caused by a new implicit transaction that is created on SQL Server. Someone could expect that ADO.NET would throw an exception that the commands are being executed on a zombie transaction. However, such exception is not thrown. (I think this is a bug in ASP.NET.) Moreover, because of zombie transaction the final Dispose() silently ignores the rollback. Any ideas, how can I ensure that nobody can execute commands on implicit transaction? Or, how to check that transaction is zombie? I found that Commit() and Rollback() check for zombie transaction, however I can call them for a test:) I also found that also reading IsolationLevel will do the check, but I am not sure whether simple calling transaction.IsolationLevel.ToString(); will not be removed by a future optimizer. Or do you know any other safe way invoke a getter (without using reflection or IL emitting)?

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  • Why compiler go to suspend mode when want to open database?

    - by rima
    Dear friend I try to connect to database with a less line for my connection string... I find out s.th in oracle website but i dont know Why when the compiler arrive to the line of open database do nothing????!it go back to GUI,but it like hanging...please help me to solve it. p.s.Its funny the program didnt get me any exception also! these service is active in my computer: > Oracle ORCL VSS Writer Service Start > OracleDBConsolrorcl > OracleJobSchedulerORCL Start > OracleOraDB11g+home1TNSListener Start > oracleServiceORCL Start try { /** * ORCL = (DESCRIPTION = (ADDRESS = (PROTOCOL = TCP)(HOST = rima-PC)(PORT = 1521)) (CONNECT_DATA = (SERVER = DEDICATED) (SERVICE_NAME = orcl) ) )*/ string oradb = "Data Source=(DESCRIPTION=" + "(ADDRESS_LIST=(ADDRESS=(PROTOCOL=TCP)(HOST=rima-PC)(PORT=1521)))" + "(CONNECT_DATA=(SERVER=DEDICATED)(SERVICE_NAME=orcl)));" + "User Id=bird_artus;Password=123456;"; //string oradb = "Data Source=OraDb;User Id=scott;Password=tiger;"; string oradb1 = "Data Source=ORCL;User Id=scott;Password=tiger;"; // C# OracleConnection con = new OracleConnection(); con.ConnectionString = oradb1; String command = "select dname from dept where deptno = 10"; MessageBox.Show(command); OracleDataAdapter oda = new OracleDataAdapter(); oda.SelectCommand = new OracleCommand(); oda.SelectCommand.Connection = con; oda.SelectCommand.CommandText = command; con.Open(); oda.SelectCommand.ExecuteNonQuery(); DataSet ds = new DataSet(); oda.Fill(ds); Console.WriteLine(ds.GetXml()); dataGridView1.DataSource = ds; con.Close(); } catch (Exception ex) { MessageBox.Show(ex.Message.ToString()+Environment.NewLine+ ex.StackTrace.ToString()); }

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  • (Not So) Silly Objective-C inheritance problem when using property - GCC Bug?

    - by Ben Packard
    Update 2 - Many people are insisting I need to declare an iVar for the property. Some are saying not so, as I am using Modern Runtime (64 bit). I can confirm that I have been successfully using @property without iVars for months now. Therefore, I think the 'correct' answer is an explanation as to why on 64bit I suddenly have to explicitly declare the iVar when (and only when) i'm going to access it from a child class. The only one I've seen so far is a possible GCC bug (thanks Yuji). Not so simple after all... Update - I messed up one line of the original copy and paste - corrected. The @property call was missing (nonatomic, retain) but is a red herring - STILL NEED AN ANSWER! Thanks. I've been scratching my head with this for a couple of hours - I haven't used inheritance much. Here I have set up a simple Test B class that inherits from Test A, where an ivar is declared. But I get the compilation error that the variable is undeclared. This only happens when I add the property and synthesize declarations - works fine without them. TestA Header: #import <Cocoa/Cocoa.h> @interface TestA : NSObject { NSString *testString; } @end TestA Implementation is empty: #import "TestA.h" @implementation TestA @end TestB Header: #import <Cocoa/Cocoa.h> #import "TestA.h" @interface TestB : TestA { } @property (nonatomic, retain) NSString *testProp; @end TestB Implementation (Error - 'testString' is undeclared) #import "TestB.h" @implementation TestB @synthesize testProp; - (void)testing{ NSLog(@"test ivar is %@", testString); } @end

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  • Loading Native library to external Package in Eclipse not working. is it a Bug?

    - by TacB0sS
    I was about to report a but to Eclipse, but I was thinking to give this a chance here first: If I add an external package, the application cannot find the referenced native library, except in the case specified at the below: If my workspace consists of a single project, and I import an external package 'EX_package.jar' from a folder outside of the project folder, I can assign a folder to the native library location via: mouse over package - right click - properties - Native Library - Enter your folder. This does not work. In runtime the application does not load the library, System.mapLibraryName(Path) also does not work. Further more, if I create a User Library, and add the package to it and define a folder for the native library it still does not. If it works for you then I have a major bug since it does not work on my computer I test this in any combination I could think of, including adding the path to the windows PATH parameter, and so many other ways I can't even start to remember, nothing worked, I played with this for hours and had a colleague try to assist me, but we both came up empty. Further more, if I have a main project that is dependent on few other projects in my workspace, and they all need to use the same 'EX_package.jar' I MUST supply a HARD COPY INTO EACH OF THEM, it will ONLY (I can't stress the ONLYNESS, I got freaked out by this) work if I have a hard copy of the package in ALL of the project folders that the main project has a dependency on, and ONLY if I configure the Native path in each of them!! This also didn't do the trick. please tell me there is a solution to this, this drives me nuts... Thanks, Adam Zehavi.

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  • Declaring a string array in class header file - compiler thinks string is variable name?

    - by Dave
    Hey everybody, I need a bit of a hand with declaring a string array in my class header file in C++. atm it looks like this: //Maze.h #include <string> class Maze { GLfloat mazeSize, mazeX, mazeY, mazeZ; string* mazeLayout; public: Maze ( ); void render(); }; and the constructor looks like this: //Maze.cpp #include <GL/gl.h> #include "Maze.h" #include <iostream> #include <fstream> Maze::Maze( ) { cin >> mazeSize; mazeLayout = new string[mazeSize]; mazeX = 2/mazeSize; mazeY = 0.25; mazeZ = 2/mazeSize; } I'm getting a compiler error that says: In file included from model-view.cpp:11: Maze.h:14: error: ISO C++ forbids declaration of ‘string’ with no type Maze.h:14: error: expected ‘;’ before ‘*’ token and the only sense that makes to me is that for some reason it thinks I want string as a variable name not as a type declaration. If anybody could help me out that would be fantastic, been looking this up for a while and its giving me the shits lol. Cheers guys

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  • NSCollectionView: Can the same object not be in the array more than once or is this a bug?

    - by Sean
    I may be doing this all wrong, but I thought I was on the right track until I hit this little snag. Basically I was putting together a toy using NSCollectionView and trying to understand how to hook that all up using IB. I have a button which will add a couple of strings to the NSArrayController: The first time I press this button, my strings appear in the collection view as expected: The second time I press the button, the views scroll down and room is made - but the items don't appear to get added. I just see blank space: The button is implemented as follows (controller is a pointer to the NSArrayController I added in IB): - (IBAction)addStuff:(id)control { [controller addObjects:[NSArray arrayWithObjects:@"String 1",@"String 2",@"String 3",nil]]; } I'm not sure what I'm doing wrong. Rather than try to explain all the connections/binds/etc, if you need more info, I'd be grateful if you could just take a quick look at the toy project itself. UPDATE: After more experimentation as suggested by James Williams, it seems the problem stems from having multiple objects with the same memory address in the array. This confuses either NSArrayController or NSCollectionView (not sure which). Changing my addStuff: to this resulted in the behavior I originally expected: [controller addObjects:[NSArray arrayWithObjects:[NSMutableString stringWithString:@"String 1"],[NSMutableString stringWithString:@"String 2"],[NSMutableString stringWithString:@"String 3"],nil]]; So the question now, I guess, is if this is a bug I should report to Apple or if this is intended/documented behavior and I just missed it?

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  • What scenarios are possible where the VS C# compiler would not compile a reference of a reference?

    - by SuperKing
    Hello, I'm probably asking this question wrong (and that may be why Google isn't helping), but here goes: In Visual Studio I am compiling a C# project (let's call it Project A, the startup project) which has a reference to Project B. Project B has a reference to a Project C, so when A gets built, the dlls for B gets placed in the bin directory of A, as does the dll for C (because B requires C, and A requires B). However, I have apparently made some change recently so that the dll for Project C does not go into the bin directory of Project A when rebuilding the solution. I have no idea what I've done to make this happen. I have not modified the setup of the solution itself, and I have only added additional references to the project files. Code wise, I have commented out most of the actual code in Project B that references classes in Project C, but did not remove the reference from the project itself (I don't think this matters). I was told that perhaps the C# compiler was optimizing somehow so that it was not building Project C, but really I'm out of ideas. I would think someone has run into something similar before Any thoughts? Thanks!

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  • Am I a discoverer of a bug in the WPF engine?

    - by bitbonk
    We have a MFC 8 application compiled with /CLR that contains a larger amount of Windows Forms UserControls wich again contain WPF user controls using ElementHost. Due to the architecture of our software we can not use HwndHost directly. We observed an extremely strange behavior here that we can not make any sense of: When the CPU load is very high during startup of the application and there are a lot live of ElementHost instances, the whole property engine completely stops working. For example animations that usually just work fine now never update the values of the bound properties, they just stay at some random value after startup. When I set a property that is not bound to anything the value is correctly stored in the dependency property (calling the getter returns the new value) but the visual representation never reflects that. I set the background to red but the background color does not change. We tested this on a lot of different machines all running Windows XP SP2 and it is pretty reproducible. The funny thing here is, that there is in fact one situation where the bound properties actually pickup a new value from the animation and the visual gets updated based on the property values. It is when I resize the ElementHost or when I hide and reshow the parent native control. As soon as I do this, properties that are bound to an animation pickup a new value and the visuals rerender based on the new property values - but just once - if I want to see another update I have to resize the ElementHost. Do you have any explanation of what could be happening here or how I could approach this problem to find it out? What can I do to debug this? Is there a way I can get more information about what WPF actually does or where WPF might have crashed? To me it currently seems like a bug in WPF itself since it only happens at high CPU load at startup.

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  • Is this a bug? Or is it a setting in ASP.NET 4 (or MVC 2)?

    - by John Gietzen
    I just recently started trying out T4MVC and I like the idea of eliminating magic strings. However, when trying to use it on my master page for my stylesheets, I get this: <link href="<%: Links.Content.site_css %>" rel="stylesheet" type="text/css" /> rending like this: <link href="&lt;%: Links.Content.site_css %>" rel="stylesheet" type="text/css" /> Whereas these render correctly: <link href="<%: Url.Content("~/Content/Site.css") %>" rel="stylesheet" type="text/css" /> <link href="<%: Links.Content.site_css + "" %>" rel="stylesheet" type="text/css" /> It appears that, as long as I have double quotes inside of the code segment, it works. But when I put anything else in there, it escapes the leading "less than". Is this something I can turn off? Is this a bug? Edit: This does not happen for <script src="..." ... />, nor does it happen for <a href="...">. Edit 2: Minimal case: <link href="<%: string.Empty %>" /> vs <link href="<%: "" %>" />

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  • Is there bug in the Matrix.RotateAt method for certain angles? .Net Winforms

    - by Jules
    Here's the code i'm using to rotate: Dim m As New System.Drawing.Drawing2D.Matrix Dim size = image.Size m.RotateAt(degreeAngle, New PointF(CSng(size.Width / 2), CSng(size.Height / 2))) Dim temp As New Bitmap(600, 600, Imaging.PixelFormat.Format32bppPArgb) Dim g As Graphics = Graphics.FromImage(temp) g.Transform = m g.DrawImage(image, 0, 0) (1) Disposals removed for brevity. (2) I test the code with a 200 x 200 rectangle. (3) Size 600,600 it just an arbitrary large value that I know will fit the right and bottom sides of the rotated image for testing purposes. (4) I know, with this code, the top and left edges will be clipped because I'm not transforming the orgin after the rotate. The problem only occurs at certain angles: (1) At 90, the right hand edge disappears completely. (2) At 180, the right and bottom edges are there, but very faded. (3) At 270, the bottom edge disappears completely. Is this a known bug? If I manually rotate the corners an draw the image by specifying an output rectangle, I don't get the same problem - though it is slightly slower than using RotateAt.

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  • Why is passing a string literal into a char* argument only sometimes a compiler error?

    - by Brian Postow
    I'm working in a C, and C++ program. We used to be compiling without the make-strings-writable option. But that was getting a bunch of warnings, so I turned it off. Then I got a whole bunch of errors of the form "Cannot convert const char* to char* in argmuent 3 of function foo". So, I went through and made a whole lot of changes to fix those. However, today, the program CRASHED because the literal "" was getting passed into a function that was expecting a char*, and was setting the 0th character to 0. It wasn't doing anything bad, just trying to edit a constant, and crashing. My question is, why wasn't that a compiler error? In case it matters, this was on a mac compiled with gcc-4.0. EDIT: added code: char * host = FindArgDefault("EMailLinkHost", ""); stripCRLF(linkHost, '\n'); where: char *FindArgDefault(char *argName, char *defVal) {// simplified char * val = defVal; return(val); } and void stripCRLF(char *str, char delim) { char *p, *q; for (p = q = str; *p; ++p) { if (*p == 0xd || *p == 0xa) { if (p[1] == (*p ^ 7)) ++p; if (delim == -1) *p = delim; } *q++ = *p; } *q = 0; // DIES HERE } This compiled and ran until it tried to set *q to 0...

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  • in haskell, why do I need to specify type constraints, why can't the compiler figure them out?

    - by Steve
    Consider the function, add a b = a + b This works: *Main> add 1 2 3 However, if I add a type signature specifying that I want to add things of the same type: add :: a -> a -> a add a b = a + b I get an error: test.hs:3:10: Could not deduce (Num a) from the context () arising from a use of `+' at test.hs:3:10-14 Possible fix: add (Num a) to the context of the type signature for `add' In the expression: a + b In the definition of `add': add a b = a + b So GHC clearly can deduce that I need the Num type constraint, since it just told me: add :: Num a => a -> a -> a add a b = a + b Works. Why does GHC require me to add the type constraint? If I'm doing generic programming, why can't it just work for anything that knows how to use the + operator? In C++ template programming, you can do this easily: #include <string> #include <cstdio> using namespace std; template<typename T> T add(T a, T b) { return a + b; } int main() { printf("%d, %f, %s\n", add(1, 2), add(1.0, 3.4), add(string("foo"), string("bar")).c_str()); return 0; } The compiler figures out the types of the arguments to add and generates a version of the function for that type. There seems to be a fundamental difference in Haskell's approach, can you describe it, and discuss the trade-offs? It seems to me like it would be resolved if GHC simply filled in the type constraint for me, since it obviously decided it was needed. Still, why the type constraint at all? Why not just compile successfully as long as the function is only used in a valid context where the arguments are in Num? Thank you.

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  • Deleted array value still showing up on foreach loop in AS3 (bug in flash?)

    - by nexus
    It took me many hours to narrow down a problem in some code to this reproducible error, which seems to me like a bug in AVM2. Can anyone shed light on why this is occurring or how to fix it? When the value at index 1 is deleted and a value is subsequently set at index 0, the non-existent (undefined) value at index 1 will now show up in a foreach loop. I have only been able to produce this outcome with index 1 and 0 (not any other n and n-1). Run this code: package { import flash.display.Sprite; public class Main extends Sprite { public function Main():void { var bar : Array = new Array(6); out(bar); //proper behavior trace("bar[1] = 1", bar[1] = 1); out(bar); //proper behavior trace("delete bar[1]", delete bar[1]); out(bar); //proper behavior trace("bar[4] = 4", bar[4] = 4); out(bar); //for each loop will now iterate over the undefined position at index 1 trace("bar[0] = 0", bar[0] = 0); out(bar); trace("bar[3] = 3", bar[3] = 3); out(bar); } private function out(bar:Array):void { trace(bar); for each(var i : * in bar) { trace(i); } } } } It will give this output: ,,,,, bar[1] = 1 1 ,1,,,, 1 delete bar[1] true ,,,,, bar[4] = 4 4 ,,,,4, 4 bar[0] = 0 0 0,,,,4, 0 undefined 4 bar[3] = 3 3 0,,,3,4, 0 undefined 4 3

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  • Django GenericRelation doesn't save related object's id - is this a bug or am I doing it wrong?

    - by pinkeen
    I have a model with a generic relation (call it A), when creating an instance of this object I pass an instance of another model (call it B) as the initializer of the content_object field (via kwargs of the constructor). If I don't save B before creating A then when saving A the content_object_id is saved to the db as NULL. If I save B before passing it to the constructor of A then everything's allright. It's not logical. I assumed that the ID of the related object (B) is fetched when doing A.save() and it should throw some kind of an exception if B isn't saved yet but it just fails silently. I don't like the current solution (saving B beforhand) because we don't know yet if I will be always willing to keep the object, not just scrap it, and there are performance considerations - what if I will add some another data and save it once more shortly after. class BaseNodeData(models.Model): ... extnodedata_content_type = models.ForeignKey(ContentType, null=True) extnodedata_object_id = models.PositiveIntegerField(null=True) extnodedata = generic.GenericForeignKey(ct_field='extnodedata_content_type', fk_field='extnodedata_object_id') class MarkupNodeData(models.Model): raw_content = models.TextField() Suppose we do: markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) markup.save() base.save() # both records are inserted to the DB but base is stored with extnodedata_object_id=NULL markup = MarkupNodeData(raw_content='...') base = BaseNodeData(..., extnodedata=markup) base.save() markup.save() # no exception is thrown and everything is the same as above markup = MarkupNodeData(raw_content='...') markup.save() base = BaseNodeData(..., extnodedata=markup) base.save() # this works as expected Of course I can do it this way, but it doesn't change anything: base = BaseNodeData(...) base.extnodedata = markup My question is - is this a bug in django which I should report or maybe I'm doing something wrong. Docs on GenericRelations aren't exactly verbose.

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