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• Pattern for UI configuration

  - by TERACytE

  I have a Win32 C++ program that validates user input and updates the UI with status information and options. Currently it is written like this: void ShowError() { SetIcon(kError); SetMessageString("There was an error"); HideButton(kButton1); HideButton(kButton2); ShowButton(kButton3); } void ShowSuccess() { SetIcon(kError); std::String statusText (GetStatusText()); SetMessageString(statusText); HideButton(kButton1); HideButton(kButton2); ShowButton(kButton3); } // plus several more methods to update the UI using similar mechanisms I do not likes this because it duplicates code and causes me to update several methods if something changes in the UI. I am wondering if there is a design pattern or best practice to remove the duplication and make the functionality easier to understand and update. I could consolidate the code inside a config function and pass in flags to enable/disable UI items, but I am not convinced this is the best approach. Any suggestions and ideas?

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• Which Stroustrup book should I use?

  - by Chris Simmons

  I'm a C# programmer that is looking to branch out. I'm bored of writing business software and want to start getting into graphics programming and games/simulators. So I figured, although writing that stuff isn't impossible in managed code, the "right" way to do that would be to look to C++, of course focussing on the language first, then getting into OpenGL or DirectX (or whatever). Way way back ('98? '99?) I had tried and failed to really grasp Stroustrup's The C++ Programming Language. I know that this book is often not recommended for the beginner. Anyway, I picked it back up (in a much more recent printing) and I'm actually getting it and enjoying it. I also have a copy of his textbook, Programming: Principles and Practice Using C++, which, as I understand it, is really geared toward teaching programming, not necessarily C++. I'm certainly not arrogant enough to claim I don't have anything more to learn about programming, data structures, algoriths, etc., however I'm not a novice there either. So my question is, with the goal of gaining the broader and more real-world-useful understanding of C++ and given my background, on which should I focus? The denser (as I perceive it) TCPPPL or the gentler Programming? EDIT: I thank everyone for the responses. However, I've got a personal choice here to make between these two books. Granted there are other very good books out there, but I'm already a good length into both of the books I mention and I'd like to finish one. So, can anyone respond on which would be the better and why? Time is not an issue; I'm not looking (at this point) at an "accelerated" read.

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• Prevent two users from editing the same data

  - by Industrial

  Hi everyone, I have seen a feature in different web applications including Wordpress (not sure?) that warns a user if he/she opens an article/post/page/whatever from the database, while someone else is editing the same data simultaneously. I would like to implement the same feature in my own application and I have given this a bit of thought. Is the following example a good practice on how to do this? It goes a little something like this: 1) User A enters a the editing page for the mysterious article X. The database tableEvents is queried to make sure that no one else is editing the same page for the moment, which no one is by then. A token is then randomly being generated and is inserted into a database table called Events. 1) User B also want's to make updates to the article X. Now since our User A already is editing the article, the Events table is queried and looks like this: | timestamp | owner | Origin | token | ------------------------------------------------------------ | 1273226321 | User A | article-x | uniqueid## | 2) The timestamp is being checked. If it's valid and less than say 100 seconds old, a message appears and the user cannot make any changes to the requested article X: Warning: User A is currently working with this article. In the meantime, editing cannot be done. Please do something else with your life. 3) If User A decides to go on and save his changes, the token is posted along with all other data to update the database, and toggles a query to delete the row with token uniqueid##. If he decides to do something else instead of committing his changes, the article X will still be available for editing in 100 seconds for User B Let me know what you think about this approach! Wish everyone a great weekend!

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• Choosing between instance methods and separate functions?

  - by StackedCrooked

  Adding functionality to a class can be done by adding a method or by defining a function that takes an object as its first parameter. Most programmers that I know would choose for the solution of adding a instance method. However, I sometimes prefer to create a separate function. For example, in the example code below Area and Diagonal are defined as separate functions instead of methods. I find it better this way because I think these functions provide enhancements rather than core functionality. Is this considered a good/bad practice? If the answer is "it depends", then what are the rules for deciding between adding method or defining a separate function? class Rect { public: Rect(int x, int y, int w, int h) : mX(x), mY(y), mWidth(w), mHeight(h) { } int x() const { return mX; } int y() const { return mY; } int width() const { return mWidth; } int height() const { return mHeight; } private: int mX, mY, mWidth, mHeight; }; int Area(const Rect & inRect) { return inRect.width() * inRect.height(); } float Diagonal(const Rect & inRect) { return std::sqrt(std::pow(static_cast<float>(inRect.width()), 2) + std::pow(static_cast<float>(inRect.height()), 2)); }

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• C# Configuration Manager . ConnectionStrings

  - by Yoda

  I have a console app containing an application configuration file containing one connection string as shown below: <configuration> <connectionStrings> <add name="Target" connectionString="server=MYSERVER; Database=MYDB; Integrated Security=SSPI;" /> </connectionStrings> </configuration> When I pass this to my Connection using: ConfigurationManager.ConnectionStrings[1].ToString() I have two values in there, hence using the second in the collection, my question is where is this second coming from? I have checked the Bin version and original and its not mine! Its obviously a system generated one but I have not seen this before? Can anyone enlighten me? The mystery connection string is: data source=.\SQLEXPRESS;Integrated Security=SSPI;AttachDBFilename=|DataDirectory|aspnetdb.mdf;User Instance=true This isn't a problem as such I would just like to know why this is occuring? Thanks in advance! For future reference to those who may or may not stumble on this, after discovering the machine.config its become apparent it is bad practice to refer to a config by its index as each stack will potentially be different, which is why "Keys" are used. Cheers all!

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• Formvalidator from the iframe.

  - by basit74

  Hello I have a following formvalidatior function in my document. function formValidator(formid) { var form = cic.$(formid); if(!form) return (''); var errors = []; var len = form.elements.length; for(var elementIdx = 0; elementIdx < len; elementIdx++) { var element = form.elements[elementIdx]; if(!element && !element.getAttribute('validationtype')) return (''); switch (element.getAttribute('validationtype')) { case 'text' : if(cic.getValue(element).strip() == "") errors.push(element.getAttribute('validationmsg')); break; case 'email' : if(!cic.isEmail(cic.getValue(element))) errors.push(element.getAttribute('validationmsg')); break; case 'numeric' : if(isNaN(cic.getValue(element).replace(',', '.'))) errors.push(element.getAttribute('validationmsg')); break; case 'confirm' : if(cic.getValue(cic.$(element.getAttribute('sourcefield'))) !== cic.getValue(element)) errors.push(element.getAttribute('validationmsg')); break; } } return (errors.length > 0) ? '<li>' + errors.uniq().join("<li>") : ''; } It works fine, now I have an Iframe in my document, and that I frame contains the form to validate. What will be the best practice to change this function in such a way that it can validate document forms and iframe from simeltaniously. Thanks

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• Usage of Assert.Inconclusive

  - by Johannes Rudolph

  Hi, Im wondering how someone should use Assert.Inconclusive(). I'm using it if my Unit test would be about to fail for a reason other than what it is for. E.g. i have a method on a class that calculates the sum of an array of ints. On the same class there is also a method to calculate the average of the element. It is implemented by calling sum and dividing it by the length of the array. Writing a Unit test for Sum() is simple. However, when i write a test for Average() and Sum() fails, Average() is likely to fail also. The failure of Average is not explicit about the reason it failed, it failed for a reason other than what it should test for. That's why i would check if Sum() returns the correct result, otherwise i Assert.Inconclusive(). Is this to be considered good practice? What is Assert.Inconclusive intended for? Or should i rather solve the previous example by means of an Isolation Framework?

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• too much recursion in javascript with jquery mouseover

  - by Stacia

  I am a JS novice. Using some code I found here to help me with mouseover scale/rotate images but now when I try to apply it to more than one object I'm getting errors saying "too much recursion". Before the function didn't take any arguments, it just was on s_1 and it worked fine. I am tempted to just write different code for each object but that isn't very good programming practice. var over = false; $(function(){ $("#s_1").hover(function(){ over = true; swing_left_anim("#s_1"); }, function(){ over = false; }); $("#np_1").hover(function(){ over = true; swing_left_anim("np_1"); }, function(){ over = false; }); }); function swing_left_anim(obj){ $(obj).animate({ rotate: '0deg' }, { duration: 500 }); if (over) { $(obj).animate({ rotate: '25deg' }, 500, swing_right_anim(obj)); } } function swing_right_anim(obj){ $(obj).animate({ rotate: '-25deg' }, 500, swing_left_anim(obj)); }

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• OS X: Terminal output of javac is garbled.

  - by Don Werve

  I've got my computer set up in Japanese (hey, it's good language practice), and everything is all fine and dandy... except javac. It displays localized error messages out to the console, but they're in Shift-JIS, not UTF8: $ javac this-file-doesnt-exist.java javac: ?t?@?C??????????????: this-file-doesnt-exist.java ?g????: javac <options> <source files> ?g?p?\??I?v?V?????~??X?g?????A-help ???g?p???? If I pipe the output through nkf -w, it's readable, but that's not really much of a solution: $ javac this-file-doesnt-exist.java 2>&1 | nkf -w javac: ????????????: this-file-doesnt-exist.java ???: javac <options> <source files> ????????????????????-help ?????? Everything else works fine (with UTF8) from the command-line; I can type filenames in Japanese, tab-completion works fine, vi can edit UTF-8 files, etc. Although java itself spits out all its messages in English (which is fine). Here's the relevant bits of my environment: LC_CTYPE=UTF-8 LANG=ja_JP.UTF-8 From what it looks like, javac isn't picking up the encoding properly, and java isn't picking up the language at all. I've tried -Dfile.encoding=utf8 as well, but that does nada, and documentation on the localization of the JVM toolchain is pretty nonexistent, at least from Google.

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• Should a Trim method generally in the Data Access Layer or with in the Domain Layer?

  - by jpierson

  I'm dealing with a database that contains data with inconsistencies such as white leading and trailing white space. In general I see a lot of developers practice defensive coding by trimming almost all strings that come from the database that may have been entered by a user at some point. In my oppinoin it is better to do such formating before data is persisted so that it is done only once and then the data can be in a consistent and reliable state. Unfortunatley this is not the case however which leads me to the next best solution, using a Trim method. If I trim all data as part of my data access layer then I don't have to concern myself with defensive trimming within the business objects of my domain layer. If I instead put the trimming responsibility in my business objects, such as with set accessors of my C# properties, I should get the same net results however the trim will be operating on all values assigned to my business objects properties not just the ones that come from the inconsistent database. I guess as a somewhat philisophical question that may determine the answer I could ask "Should the domain later be responsible for defensive/coercive formatting of data?" Would it make sense to have a set accessor for a PhoneNumber property on a business object accept a unformatted or formatted string and then attempt to format it as required or should this responsibility be pushed to the presentation and data access layers leaving the domain layer more strict in the type of data that it will accept? I think this may be the more fundamental question. Update: Below are a few links that I thought I should share about the topic of data cleansing. Information service patterns, Part 3: Data cleansing pattern LINQ to SQL - Format a string before saving? How to trim values using Linq to Sql?

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• What is the Proper approach for Constructing a PhysicalAddress object from Byte Array

  - by Paul Farry

  I'm trying to understand what the correct approach for a constructor that accepts a Byte Array with regard to how it stores it's data (specifically with PhysicalAddress) I have an array of 6 bytes (theAddress) that is constructed once. I have a source array of 18bytes (theAddresses) that is loaded from a TCP Connection. I then copy the 6bytes from theAddress+offset into theAddress and construct the PhysicalAddress from it. Problem is that the PhysicalAddress just stores the Reference to the array that was passed in. Therefore if you subsequently check the addresses they only ever point to the last address that was copied in. When I took a look inside the PhysicalAddress with reflector it's easy to see what's going on. public PhysicalAddress(byte[] address) { this.changed = true; this.address = address; } Now I know this can be solved by creating theAddress array on each pass, but I wanted to find out what really is the best practice for this. Should the constructor of an object that accepts a byte array create it's own private Variable for holding the data and copy it from the original Should it just hold the reference to what was passed in. Should I just created theAddress on each pass in the loop

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• Why would ASP.NET MVC use session state?

  - by ray247

  Recommended by the ASP.NET team to use cache instead of session, we stopped using session from working with the WebForm model the last few years. So we normally have the session turned off in the web.config <sessionState mode="Off" /> But, now when I'm testing out a ASP.NET MVC application with this setting it throw an error in class SessionStateTempDataProvider inside the mvc framework, it asked me to turn on session state, I did and it worked. Looking at the source it uses session Dictionary<string, object> tempDataDictionary = httpContext.Session[TempDataSessionStateKey] as Dictionary<string, object>; // line 20 in SessionStateTempDataProvider.cs So, why would they use session here? What am I missing? Thanks, Ray. ======================================================== Edit Sorry didn't mean for this post to debate on session vs. cache, but rather in the context of the ASP.NET MVC, I was just wondering why session is used here. In this Scott Watermasysk blog post he mentioned on turning off session too as a good practice, so I'm just wondering do I have to turn it on to use MVC from here on?

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• Is there a standard pattern for scanning a job table executing some actions?

  - by Howiecamp

  (I realize that my title is poor. If after reading the question you have an improvement in mind, please either edit it or tell me and I'll change it.) I have the relatively common scenario of a job table which has 1 row for some thing that needs to be done. For example, it could be a list of emails to be sent. The table looks something like this: ID Completed TimeCompleted anything else... ---- --------- ------------- ---------------- 1 No blabla 2 No blabla 3 Yes 01:04:22 ... I'm looking either for a standard practice/pattern (or code - C#/SQL Server preferred) for periodically "scanning" (I use the term "scanning" very loosely) this table, finding the not-completed items, doing the action and then marking them completed once done successfully. In addition to the basic process for accomplishing the above, I'm considering the following requirements: I'd like some means of "scaling linearly", e.g. running multiple "worker processes" simultaneously or threading or whatever. (Just a specific technical thought - I'm assuming that as a result of this requirement, I need some method of marking an item as "in progress" to avoid attempting the action multiple times.) Each item in the table should only be executed once. Some other thoughts: I'm not particularly concerned with the implementation being done in the database (e.g. in T-SQL or PL/SQL code) vs. some external program code (e.g. a standalone executable or some action triggered by a web page) which is executed against the database Whether the "doing the action" part is done synchronously or asynchronously is not something I'm considering as part of this question.

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• Application.ProcessMessages hangs???

  - by X-Ray

  my single threaded delphi 2009 app (not quite yet complete) has started to have a problem with Application.ProcessMessages hanging. my app has a TTimer object that fires every 100 ms to poll an external device. i use Application.ProcessMessages to update the screen when something changes so the app is still responsive. one of these was in a grid OnMouseDown event. in there, it had an Application.ProcessMessages that essentially hung. removing that was no problem except that i soon discovered another Application.ProcessMessages that was also blocking. i think what may be happening to me is that the TTimer is--in the app mode i'm currently debugging--probably taking too long to complete. i have prevented the TTimer.OnTimer event hander from re-entering the same code (see below): procedure TfrmMeas.tmrCheckTimer(Sender: TObject); begin if m_CheckTimerBusy then exit; m_CheckTimerBusy:=true; try PollForAndShowMeasurements; finally m_CheckTimerBusy:=false; end; end; what places would it be a bad practice to call Application.ProcessMessages? OnPaint routines springs to mind as something that wouldn't make sense. any general recommendations? i am surprised to see this kind of problem arise at this point in the development!

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• Agile language for 2d game prototypes?

  - by instanceofTom

  Occasionally ( read: when my fiancé allows ) I like to prototype different game or game-like ideas I have. Usually I use Java or C# (not xna yet) because they are the languages I have the most practice with. However I would like to learn something more suited to agile development; a language in which it would be easier to knock out quick prototypes. At my job I have recently been working with looser (weak/dynamically typed) languages, specifically python and groovy, and I think something similar would fit what I am looking for. So, my question is: What languages (and framework/engine) would be good for rapidly developing prototypes of 2d game concepts? A few notes: I don't need blazing fast bitcrunching performance. In this case I would strongly prefer ease of development over performance. I'd like to use a language with a healthy community, which to me means a fair amount of maintained 3rd party, libraries. I'd like the language to be cross-platform friendly, I work on a variety of different operating systems and would like something that is portable with minimum effort. I can't imagine myself using a language with out decent options for debugging and editor syntax highlighting support. Note: If you are aware of a Java or C# library/framework that you think streamlines producing game prototypes I open to learning something new for those languages too

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• C/C++ Control Structure Limitations?

  - by STingRaySC

  I have heard of a limitation in VC++ (not sure which version) on the number of nested if statements (somewhere in the ballpark of 300). The code was of the form: if (a) ... else if (b) ... else if (c) ... ... I was surprised to find out there is a limit to this sort of thing, and that the limit is so small. I'm not looking for comments about coding practice and why to avoid this sort of thing altogether. Here's a list of things that I'd imagine could have some limitation: Number of functions in a scope (global, class, or namespace). Number of expressions in a single statement (e.g., compound conditionals). Number of cases in a switch. Number of parameters to a function. Number of classes in a single hierarchy (either inheritance or containment). What other control structures/language features have limits such as this? Do the language standards say anything about these limits (perhaps minimum requirements for an implementation)? Has anyone run into a particular language limitation like this with a particular compiler/implementation? EDIT: Please note that the above form of if statements is indeed "nested." It is equivalent to: if (a) { //... } else { if (b) { //... } else { if (c) { //... } else { //... } } }

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• How to not use JavaScript with in the elements events attributes but still load via AJAX

  - by thecoshman

  I am currently loading HTMl content via AJAX. I have code for things on different elements onclick attributes (and other event attributes). It does work, but I am starting to find that the code is getting rather large, and hard to read. I have also read that it is considered bad practice to have the event code 'inline' like this and that I should really do by element.onclick = foobar and have foobar defined somewhere else. I understand how with a static page it is fairly easy to do this, just have a script tag at the bottom of the page and once the page is loaded have it executed. This can then attach any and all events as you need them. But how can I get this sort of affect when loading content via AJAX. There is also the slight case that the content loaded can very depending on what is in the database, some times certain sections of HTML, such as tables of results, will not even be displayed there will be something else entirely. I can post some samples of code if any body needs them, but I have no idea what sort of things would help people with this one. I will point out, that I am using Jquery already so if it has some helpful little functions that would be rather sweet¬

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• Where in maven project's path should I put configuration files that are not considered resources

  - by Paralife

  I have a simple java maven project. One of my classes when executing needs to load an xml configuration file from the classpath. I dont want to package such xml file when producing the jar but I want to include a default xml file in a zip assemply under a conf subfolder and I also want this default xml to be available in the unit tests to test against it. As I see it there are 2 possible places of this default xml: src/main/resources/conf/default.xml src/main/conf/default.xml Both solutions demand special pom actions: In solution 1, I get the auto copy to target folder during build which means it is available in testing but I also get it in the produced jar which i dont want. In solution 2, I get the jar as I want it(free of the xml) but I manually have to copy the xml to the target folder to be available for testing. (I dont want to add src's subfolders in test classpath. I think it is bad practice). The question is what is the best solution of the two? If the correct is 2, what is the best way to copy it to target folder? Is there any other solution better and more common than those two? (I also read http://stackoverflow.com/questions/465001/where-should-i-put-application-configuration-files-for-a-maven-project but I would like to know the most "correct solution" from the "convention over configuration" point of view and this link provides some configuration type solutions but not any convention oriented. Maybe there isnt one but I ask anyway. Also the solutions provided include AntRun plugin and appAssembler plugin and I wonder if I could do it with out them.)

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• git rebase without changing commit timestamps

  - by Olivier

  Would it make sense to perform git rebase while preserving the commit timestamps? I believe a consequence would be that the new branch will not necessarily have commit dates chronologically. Is that theoretically possible at all? (e.g. using plumbing commands; just curious here) If it is theoretically possible, then is it possible in practice with rebase, not to change the timestamps? For example, assume I have the following tree: master <jun 2010> | : : : oldbranch <feb 1984> : / oldcommit <jan 1984> Now, if I rebase oldbranch on master, the date of the commit changes from feb 1984 to jun 2010. Is it possible to change that behaviour so that the commit timestamp is not changed? In the end I would thus obtain: oldbranch <feb 1984> / master <jun 2010> | : Would that make sense at all? Is it even allowed in git to have a history where an old commit has a more recent commit as a parent? Edit A crucial question of Von C helped me understand what is going on: when your rebase, the committer's timestamp changes, but not the author's timestamp, which suddenly all makes sense. So my question was actually not precise enough. The answer is that rebase actually doesn't change the author's timestamps (you don't need to do anything for that), which suits me perfectly.

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• Utility of List<T>.Sort() versus List<T>.OrderBy() for a member of a custom container class

  - by ccomet

  I've found myself running back through some old 3.5 framework legacy code, and found some points where there are a whole bunch of lists and dictionaries that must be updated in a synchronized fashion. I've determined that I can make this process infinitely easier to both utilize and understand by converging these into custom container classes of new custom classes. There are some points, however, where I came to concerns with organizing the contents of these new container classes by a specific inner property. For example, sorting by the ID number property of one class. As the container classes are primarily based around a generic List object, my first instinct was to write the inner classes with IComparable, and write the CompareTo method that compares the properties. This way, I can just call items.Sort() when I want to invoke the sorting. However, I've been thinking instead about using items = items.OrderBy(Func) instead. This way it is more flexible if I need to sort by any other property. Readability is better as well, since the property used for sorting will be listed in-line with the sort call rather than having to look up the IComparable code. The overall implementation feels cleaner as a result. I don't care for premature or micro optimization, but I like consistency. I find it best to stick with one kind of implementation for as many cases as it is appropriate, and use different implementations where it is necessary. Is it worth it to convert my code to use the LINQ OrderBy instead of using List.Sort? Is it a better practice to stick with the IComparable implementation for these custom containers? Are there any significant mechanical advantages offered by either path that I should be weighing the decision on? Or is their end-functionality equivalent to the point that it just becomes coder's preference?

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• Passing arguments and values from HTML to jQuery (events)

  - by Jaroslav Moravec

  What is the practice to pass arguments from HTML to jQuery events function. For example getting id of row from db: <tr class="jq_killMe" id="thisItemId-id"> ... </tr> and jQuery: $(".jq_killMe").click(function () { var tmp = $(this).attr('id).split("-"); var id = tmp[0] // ... } What's the best practise, if I want to pass more than one argument? Is it better not to use jQuery? For example: <tr onclick="killMe('id')"> ... </tr> I didn't find the answer on my question, I will be glad even for links. Thanks. Edit (pre solution) So you suggested two methods to do that: Add custom attributes to element (XHTML) Use attribute ID and parse it by regex Attribute data-* attributes in HTML5 Use hidden children elements I like first solution, but... I would like to (I have to (employer)) produce valid code. Here is a nice question and answers: http://stackoverflow.com/questions/994856/so-what-if-custom-html-attributes-arent-valid-xhtml And the second is not so pretty as the first, but valid. So the compromise is... The third is the solution for future, but here is a lot of CMS where we have to use XHTML or HTML4. (And HTML5 is the long process)

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• How do I interact with a Perl object that has a hash attribute?

  - by brydgesk

  I have a class with several variables, one of which is a hash (_runs): sub new { my ($class, $name) = @_; my $self = { _name => $name, ... _runs => (), _times => [], ... }; bless ($self, $class); return $self; } Now, all I'm trying to do is create an accessor/mutator, as well as another subroutine that pushes new data into the hash. But I'm having a hell of a time getting all the referencing/dereferencing/$self calls working together. I've about burned my eyes out with "Can't use string ("blah") as a HASH ref etc etc" errors. For the accessor, what is 'best practice' for returning hashes? Which one of these options should I be using (if any)?: return $self->{_runs}; return %{ $self->{_runs} }; return \$self->{_runs}; Further, when I'm using the hash within other subroutines in the class, what syntax do I use to copy it? my @runs = $self->{_runs}; my @runs = %{ $self->{_runs} }; my @runs = $%{ $self->{_runs} }; my @runs = $$self->{_runs}; Same goes for iterating over the keys: foreach my $dt (keys $self->{_runs}) foreach my $dt (keys %{ $self->{_runs} }) And how about actually adding the data? $self->{_runs}{$dt} = $duration; %{ $self->{_runs} }{$dt} = $duration; $$self->{_runs}{$dt} = $duration; You get the point. I've been reading articles about using classes, and articles about referencing and dereferencing, but I can't seem to get my brain to combine the knowledge and use both at the same time. I got my _times array working finally, but mimicking my array syntax over to hashes didn't work.

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• pure/const functions in C++

  - by Albert

  Hi, I'm thinking of using pure/const functions more heavily in my C++ code. (pure/const attribute in GCC) However, I am curious how strict I should be about it and what could possibly break. The most obvious case are debug outputs (in whatever form, could be on cout, in some file or in some custom debug class). I probably will have a lot of functions, which don't have any side effects despite this sort of debug output. No matter if the debug output is made or not, this will absolutely have no effect on the rest of my application. Or another case I'm thinking of is the use of my own SmartPointer class. In debug mode, my SmartPointer class has some global register where it does some extra checks. If I use such an object in a pure/const function, it does have some slight side effects (in the sense that some memory probably will be different) which should not have any real side effects though (in the sense that the behaviour is in any way different). Similar also for mutexes and other stuff. I can think of many complex cases where it has some side effects (in the sense of that some memory will be different, maybe even some threads are created, some filesystem manipulation is made, etc) but has no computational difference (all those side effects could very well be left out and I would even prefer that). How does it work out in practice? If I mark such functions as pure/const, could it break anything (considering that the code is all correct)?

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• Differences between Assembly Code output of the same program

  - by ultrajohn

  I have been trying to replicate the buffer overflow example3 from this article aleph one I'm doing this as a practice for a project in a computer security course i'm taking so please, I badly need your help. I've been the following the example, performing the tasks as I go along. My problem is the assembly code dumped by gdb in my computer (i'm doing this on a debian linux image running on VM Ware) is different from that of the example in the article. There are some constructs which I find confusing. Here is the one from my computer: here is the one from the article... Dump of assembler code for function main: 0x8000490 <main>: pushl %ebp 0x8000491 <main+1>: movl %esp,%ebp 0x8000493 <main+3>: subl $0x4,%esp 0x8000496 <main+6>: movl $0x0,0xfffffffc(%ebp) 0x800049d <main+13>: pushl $0x3 0x800049f <main+15>: pushl $0x2 0x80004a1 <main+17>: pushl $0x1 0x80004a3 <main+19>: call 0x8000470 <function> 0x80004a8 <main+24>: addl $0xc,%esp 0x80004ab <main+27>: movl $0x1,0xfffffffc(%ebp) 0x80004b2 <main+34>: movl 0xfffffffc(%ebp),%eax 0x80004b5 <main+37>: pushl %eax 0x80004b6 <main+38>: pushl $0x80004f8 0x80004bb <main+43>: call 0x8000378 <printf> 0x80004c0 <main+48>: addl $0x8,%esp 0x80004c3 <main+51>: movl %ebp,%esp 0x80004c5 <main+53>: popl %ebp 0x80004c6 <main+54>: ret 0x80004c7 <main+55>: nop As you can see, there are differences between the two. I'm confuse and I can't understand totally the assembly code from my computer. I would like to know the differences between the two. How is pushl different from push, mov vs movl , and so on... what does the expression 0xhexavalue(%register) means? I am sorry If I'm asking a lot, But I badly need your help. Thanks for the help really...

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• What is wrong with accessing DBI directly?

  - by canavanin

  Hi everyone! I'm currently reading Effective Perl Programming (2nd edition). I have come across a piece of code which was described as being poorly written, but I don't yet understand what's so bad about it, or how it should be improved. It would be great if someone could explain the matter to me. Here's the code in question: sub sum_values_per_key { my ( $class, $dsn, $user, $password, $parameters ) = @_; my %results; my $dbh = DBI->connect( $dsn, $user, $password, $parameters ); my $sth = $dbh->prepare( 'select key, calculate(value) from my_table'); $sth->execute(); # ... fill %results ... $sth->finish(); $dbh->disconnect(); return \%results; } The example comes from the chapter on testing your code (p. 324/325). The sentence that has left me wondering about how to improve the code is the following: Since the code was poorly written and accesses DBI directly, you'll have to create a fake DBI object to stand in for the real thing. I have probably not understood a lot of what the book has so far been trying to teach me, or I have skipped the section relevant for understanding what's bad practice about the above code... Well, thanks in advance for your help!

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