Search Results

Search found 6342 results on 254 pages for 'behavior'.

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

Page 22/254 | < Previous Page | 18 19 20 21 22 23 24 25 26 27 28 29  | Next Page >

  • Strange PHP array behavior overwriting values with all the same values

    - by dasdas
    Im doing a simple mysqli query with code ive used many times before but have never had this problem happen to me. I am grabbing an entire table with an unknown number of columns (it changes often so i dont know the exact value, nor the column names). I have some code that uses metadata to grab everything and stick it in an array. This all works fine, but the output is messed up: $stmt -> execute(); //the query is legit, no problems there $meta = $stmt->result_metadata(); while ($field = $meta->fetch_field()) { $params[] = &$row[$field->name]; } call_user_func_array(array($stmt, 'bind_result'), $params); while ($stmt->fetch()) { $pvalues[++$i] = $row; //$pvalues is an array of arrays. row is an array //print_r($row); print_r($pvalues[$i-1]); } $stmt -> close(); I would assume that $pvalues has the results that I am looking for. My table currently has 2 rows. $pvalues has array length 2. Both rows in $pvalues are exactly the same. If i use the: print_r($row) it prints out the correct values for both rows, but if later on i check what is in $pvalues it is incorrect (1 row is assigned to both indices of $pvalues). If i use the print_r($pvalues[$i-1]) it prints exactly as I expect, the same row in the table twice. Why isnt the data getting assigned to $pvalues? I know $row holds the right information at one point, but it is getting overwritten or lost.

    Read the article

  • strange behavior of <> to filter null values

    - by Kerezo
    Hi experts: I have a table Called tblAlarm and it has some records like this: I have another table for determine what user see what message: Now I want to write a query to show Messages that user has not seen if message didinot expired.(for example it's year between BeginYear and EndYear and so on ...). I write this query: SELECT * FROM tblAlarms LEFT OUTER JOIN tblUsersAlarms tua ON tblAlarms.Id=tua.MessageID WHERE @CurrentYear BETWEEN tblAlarms.BeginYear AND tblAlarms.EndYear AND @CurrentMonth BETWEEN tblAlarms.BeginMonth AND tblAlarms.EndMonth AND @CurrentDay BETWEEN tblAlarms.BeginDay AND tblAlarms.EndDay AND (@CurrentHour * 60 + @CurrentMinute) BETWEEN tblAlarms.BeginHour*60 + tblAlarms.BeginMinute AND tblAlarms.EndHour*60 + tblAlarms.EndMinute --AND (tua.UserID <> 128 AND tua.UserID IS NULL) and it returns : but if I unComment last line it does not return any record.How I can determine what messages that users has not been seen? thanks

    Read the article

  • weird index behavior

    - by TasostheGreat
    I have set up my table with an index only on done_status(done_status =INT), when I use EXPLAIN SELECT * FROM reminder WHERE done_status=2 i get this back id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE reminder ALL done_status NULL NULL NULL 5 Using where but when I give this command EXPLAIN SELECT * FROM reminder WHERE done_status=1 that's what I get back: id select_type table type possible_keys key key_len ref rows Extra 1 SIMPLE reminder ref done_status done_status 4 const 2 first time it shows me it uses 5 rows second time 2 rows I don't think the index works, if I understood it right first time it should give me 3 rows. What do I do wrong? SHOW INDEX FROM reminder: Table Non_unique Key_name Seq_in_index Column_name Collation Cardinality Sub_part Packed Null Index_type Comment Index_comment reminder 1 done_status 1 done_status A 5 NULL NULL BTREE

    Read the article

  • KnpLabs / DoctrineBehaviors Translatable - currentLocale = null

    - by Ruben
    Using the trait \Knp\DoctrineBehaviors\Model\Translatable\Translation inside an Entity, I see that the property currentLocale is never setted , so we always obtain the default locale ('en') in all the calls to $this->translate(). If I change this getDefaultLocale, all the translations are made correctly, so I think that is no problem with the fallback. I tried debug the currentLocaleCallable. I see that if I put a "var_dump ($this-container-get('request'));" in the contructor of currentLocaleCallable, the request have a locale to null. And outside the request has the correct locale.It seems that container is not in the scope: request , i don't know how can I get it to work I post an issue in github https://github.com/KnpLabs/DoctrineBehaviors/issues/71 EDITED This service is defined in vendor/knplabs/doctrine-behaviors/config/orm-services.yml and is: knp.doctrine_behaviors.reflection.class_analyzer: class: "%knp.doctrine_behaviors.reflection.class_analyzer.class%" public: false knp.doctrine_behaviors.translatable_listener: class: "%knp.doctrine_behaviors.translatable_listener.class%" public: false arguments: - "@knp.doctrine_behaviors.reflection.class_analyzer" - "%knp.doctrine_behaviors.reflection.is_recursive%" - "@knp.doctrine_behaviors.translatable_listener.current_locale_callable" tags: - { name: doctrine.event_subscriber } knp.doctrine_behaviors.translatable_listener.current_locale_callable: class: "%knp.doctrine_behaviors.translatable_listener.current_locale_callable.class%" arguments: - "@service_container" # lazy request resolution public: false EDIT 2: My composer.json "php": ">=5.3.3", "symfony/symfony": "2.3.*", "doctrine/orm": ">=2.2.3,<2.4-dev", "doctrine/doctrine-bundle": "1.2.*", "twig/extensions": "1.0.*", "symfony/assetic-bundle": "2.3.*", "symfony/swiftmailer-bundle": "2.3.*", "symfony/monolog-bundle": "2.3.*", "sensio/distribution-bundle": "2.3.*", "sensio/framework-extra-bundle": "2.3.*", "sensio/generator-bundle": "2.3.*", "incenteev/composer-parameter-handler": "~2.0", "friendsofsymfony/user-bundle": "1.3.*", "avalanche123/imagine-bundle": "v2.1", "raulfraile/ladybug-bundle": "~1.0", "genemu/form-bundle": "2.2.*", "friendsofsymfony/rest-bundle": "0.12.0", "stof/doctrine-extensions-bundle": "dev-master", "sonata-project/admin-bundle": "dev-master", "a2lix/translation-form-bundle": "1.*@dev", "sonata-project/user-bundle": "dev-master", "psliwa/pdf-bundle": "dev-master", "jms/serializer-bundle": "dev-master", "jms/di-extra-bundle": "dev-master", "knplabs/doctrine-behaviors": "dev-master", "sonata-project/doctrine-orm-admin-bundle": "dev-master", "knplabs/knp-paginator-bundle": "dev-master", "friendsofsymfony/jsrouting-bundle": "~1.1", "zendframework/zend-validator": ">=2.0.0-rc2", "zendframework/zend-barcode": ">=2.0.0-rc2"

    Read the article

  • Silverlight DataStateBehavior, initial value not used

    - by JimmySavile
    Hi, I am trying to use the Silverlight DataStateBehavior, it works fine in most cases where I click a button which sets say a 'Selected' Property in the view model to either false or true. The DataStateBehavior then tells the VisualStateManager to go to the relevant state. Like this: <Button...> <i:Interaction.Behaviors> <id:DataStateBehavior Binding="{Binding Selected}" Value="True" TrueState="SelectedVisualState" FalseState="DeselectedVisualState"/> </i:Interaction.Behaviors> </Button> The above works fine. What I am trying to do though is to get it to set the correct state when the application loads, if I were to set the 'Selected' property on the view model to true by default I wouldn't see any changes in the UI until I clicked the button to change the viewmodel property. I know there are several classes involved with the DataState stuff including: BindingListener.cs ConverterHelper.cs DataStateBehavior.cs DataStateSwitchBehavior.cs DataTrigger.cs Any clues would be good, Thanks

    Read the article

  • Wicket: stateless AJAX behaviors in stateful page without serialization

    - by mschayna
    I have pretty stateful page with plenty of AJAX components. Most of these components have behaviors, which renders JavaScript code for calling AJAX requests to Java code. Because page isn't stateless, each request causes serialization of page. So far so good. But some of these AJAX requests doesn't change page ever, so serialization of page isn't necessary. For example it is forward caching data for (home-brewed) datagrid component. These requests are calling continuously and serialization of page during each request causes delays. There are some projects for stateless wicket components out there, e.g. wicket-stateless, but it solves another situation -- request of stateless components are processed on new instances of stateless pages. I want to process requests on existing stateful page instance but without serialization. I have tried to implement this in my own RequestCycleProcessor.resolve(), but I hung on searching for page from requestParameters because Session.getPage() always touches page and it causes serialization after request processing. Is there any example, idea, whatever for implementing this in Wicket? Hope it's understandable :)

    Read the article

  • Segmentation fault in strcpy

    - by Alien01
    consider the program below char str[5]; strcpy(str,"Hello12345678"); printf("%s",str); When run this program gives segmentation fault. But when strcpy is replaced with following, program runs fine. strcpy(str,"Hello1234567"); So question is it should crash when trying to copy to str any other string of more than 5 chars length. So why it is not crashing for "Hello1234567" and only crashing for "Hello12345678" ie of string with length 13 or more than 13. This program was run on 32 bit machine .

    Read the article

  • C++ Exceptions and Inheritance from std::exception

    - by fbrereto
    Given this sample code: #include <iostream> #include <stdexcept> class my_exception_t : std::exception { public: explicit my_exception_t() { } virtual const char* what() const throw() { return "Hello, world!"; } }; int main() { try { throw my_exception_t(); } catch (const std::exception& error) { std::cerr << "Exception: " << error.what() << std::endl; } catch (...) { std::cerr << "Exception: unknown" << std::endl; } return 0; } I get the following output: Exception: unknown Yet simply making the inheritance of my_exception_t from std::exception public, I get the following output: Exception: Hello, world! Could someone please explain to me why the type of inheritance matters in this case? Bonus points for a reference in the standard.

    Read the article

  • Merge entries in CakePHP

    - by Andrea
    Let's say I have a Model, for example User, and I want to merge two instances of this Model, say merge User2 into User1. Explicitly this is what I mean: If a field is already filled in User1, it should remain the same If a field is missing in User1 but is present in User2, it should be copied If SomeModel BelongsTo User, every instance of SomeModel pointing to User2 should be modified to point to User1 Same if SomeModel HasAndBelongsToMany User If SomeModel HasMany User, and SomeModel1 Has User2 but no other instance Has User1, it should be modified so that SomeModel1 has User1 instead If SomeModel HasMany User, SomeModel1 Has User1 and SomeModel2 Has User2... well, I'm not sure here, I guess the only solution is to discard SomeModel2, since User1 can BelongTo only one SomeModel. Finally User2 should be removed. Is there a way to automate this? Maybe a Behaviour? If not, I may consider creating it, since I will need it a lot.

    Read the article

  • In Ruby, how to implement global behaviour?

    - by Gordon McAllister
    Hi all, I want to implement the concept of a Workspace. This is a global concept - all other code will interact with one instance of this Workspace. The Workspace will be responsible for maintaining the current system state (i.e. interacting with the system model, persisting the system state etc) So what's the best design strategy for my Workspace, bearing in mind this will have to be testable (using RSpec now, but happy to look at alternatives). Having read thru some open source projects out there and I've seen 3 strategies. None of which I can identify as "the best practice". They are: Include the singleton class. But how testable is this? Will the global state of Workspace change between tests? Implemented all behaviour as class methods. Again how do you test this? Implemented all behaviour as module methods. Not sure about this one at all! Which is best? Or is there another way? Thanks, Gordon

    Read the article

  • Strange php behaviour on a gd function

    - by mck89
    Hi, i met a very strange PHP behaviour, i don't understand why it behaves like this. I'm using the imagesetbrush function in this way: class foo { function setbrush($image) { //$this->_resource contains the main image resource imagesetbrush($this->_resource, $image); } } ... $res=imagecreatefrompng("image.png"); $class->setbrush($res); in this way it works, but if i change the code like this: class foo { function setbrush($image) { $res=imagecreatefrompng($image); imagesetbrush($this->_resource, $res); } } ... $class->setbrush("image.png"); it doesn't work anymore. Do you see some error? It doesn't show me any message it simply doesn't execute the function.

    Read the article

  • Deleting a resource in a Cucumber (Capybara) step doesn't work

    - by Josiah Kiehl
    Here is my Scenario: Scenario: Delete a match Given pojo is logged in And there is a match with the following: | game_id | 1 | | name | Game del Pojo | | date_and_time | 2010-02-23 17:52:00 | | players | 2 | | teams | 2 | | comment | This is an awesome comment | | user_id | 1 | And I am on the show match 1 page And show me the page When I follow "Delete" And I follow "Yes, delete it" Then there should not be a match with the following: | game_id | 1 | | name | Game del Pojo | | date_and_time | 2010-02-23 17:52:00 | | players | 2 | | teams | 2 | | comment | This is an awesome comment | | user_id | 1 | If I walk through these steps manually, they work. When I click the confirmation: Yes, delete it, then the match is deleted. Cucumber, however, fails to delete the record and the last step fails. And I follow "Yes, delete it" # features/step_definitions/web_steps.rb:32 Then there should not be a match with the following: # features/step_definitions/match_steps.rb:8 | game_id | 1 | | name | Game del Pojo | | date_and_time | 2010-02-23 17:52:00 | | players | 2 | | teams | 2 | | comment | This is an awesome comment | | user_id | 1 | <nil> expected but was <#<Match id: 1, name: "Game del Pojo", date_and_time: "2010-02-23 17:52:00", teams: 2, created_at: "2010-03-02 23:06:33", updated_at: "2010-03-02 23:06:33", comment: "This is an awesome comment", players: 2, game_id: 1, user_id: 1>>. (Test::Unit::AssertionFailedError) /usr/lib/ruby/1.8/test/unit/assertions.rb:48:in `assert_block' /usr/lib/ruby/1.8/test/unit/assertions.rb:495:in `_wrap_assertion' /usr/lib/ruby/1.8/test/unit/assertions.rb:46:in `assert_block' /usr/lib/ruby/1.8/test/unit/assertions.rb:83:in `assert_equal' /usr/lib/ruby/1.8/test/unit/assertions.rb:172:in `assert_nil' ./features/step_definitions/match_steps.rb:22:in `/^there should (not)? be a match with the following:$/' features/matches.feature:124:in `Then there should not be a match with the following:' Any clue how to debug this? Thanks!

    Read the article

  • Is it safe to catch an access violation in this scenario?

    - by Eloff
    I've read a lot, including here on SO that suggests this is a very bad idea in general and that the only thing you can do safely is exit the program. I'm not sure that this is true. This is for a pooling memory allocator that hands off large allocations to malloc. During pool_free() a pointer needs to be checked it it belongs to a pool or was allocated with malloc. By rounding the address down to the nearest 1MB boundary, I get a pointer to the beginning of a block of memory in the pool, or undefined if malloc was used. In the first case I can easily verify that the block of memory belongs to the pool, but, if it does not I will either fail this verification, or I will get an access violation (note that this is a read-only process). Could I not catch this with SEH (Windows) or handle the signal (POSIX) and simply treat it as a failed verification? (i.e. this is only possible if malloc was used, so pass the ptr to free())

    Read the article

  • Constraining to parent container with MouseDragElementBehavior

    - by anonymous
    Hi all, I just had a question regarding constraining a control's drag and drop movement to its parent canvas. I tried using the ConstrainToParentBounds property on the MouseDragElementBehavior, however, when this is used the drag must be done really slowly or the movement of the control is choppy or stops altogether. So I am attempting to implement my own boundary constraints. I seem to be running into difficulty though. I am still using the MouseDragElementBehavior but am attempting to supplement it by also handling mouseleftbuttondown, mousemove, mouseleftbuttonup events. I know that these are working (haven't been overridden by the MouseDragElementBehavior) as I have tested them using other methods. I will post my current code below: private void Control_MouseMove(object sender, MouseEventArgs e) { MyControl mc = (MyControl)sender; Canvas canvas = (Canvas)mc.parent; GeneralTransform ct = canvas.TransformToVisual(Application.Current.RootVisual as UIElement; Point canvas_offset = ct.Transform(new Point(0,0)); double canvasTop = canvas_offset.Y; double canvasLeft = canvas_offset.X; GeneralTransform gt = mc.TransformToVisual(Application.Current.RootVisual as UIElement); Point offset = gt.Transform(new Point(0,0)); double controlTop = offset.Y; double controlLeft = offset.X; if(isMouseCaptured) { if(controlTop < canvasTop) { mc.Opacity = 1; //to test if conditions are being met, seems to indicate ok mc.setValue(Canvas.TopProperty, canvasTop); } if(controlLeft < canvasLeft) { mc.Opacity = 1; mc.setValue(Canvas.TopProperty, canvasTop); } } } This is what my code looks like at the moment (I realize there is nothing there for right/bottom). I've tried a bunch of different things at this point and none of them seem to give the desired result; the control's movement is still not constrained to the canvas. Any help/pointers would be greatly appreciated. Thanks!

    Read the article

  • Why in Ruby, a || 1 will throw an error when `a` is undefined, but a = a || 1 will not?

    - by Jian Lin
    When a is undefined, then a || 1 will throw an error, but a = a || 1 will not. Isn't that a little bit inconsistent? irb(main):001:0> a NameError: undefined local variable or method `a' for main:Object from (irb):1 from c:/ruby/bin/irb:12:in `<main>' irb(main):002:0> a || 1 NameError: undefined local variable or method `a' for main:Object from (irb):2 from c:/ruby/bin/irb:12:in `<main>' irb(main):003:0> a = a || 1 => 1

    Read the article

  • 3.1.3 and 3.2 different behaviour

    - by teo
    I'm using a custom cell in tableView with a UITextField - (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath { static NSString *CellIdentifier = @"Cell"; UITableViewCell *cell = [tableView dequeueReusableCellWithIdentifier:CellIdentifier]; if (cell == nil) { cell = [[[UITableViewCell alloc] initWithStyle:UITableViewCellStyleSubtitle reuseIdentifier:CellIdentifier] autorelease]; UITextField *txtField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 280, 24)]; txtField.placeholder = @"<Enter Text>"; txtField.textAlignment = UITextAlignmentLeft; txtField.clearButtonMode = UITextFieldViewModeAlways; txtField.autocapitalizationType = UITextAutocapitalizationTypeNone; txtField.autocorrectionType = UITextAutocorrectionTypeNo; [cell.contentView addSubview:txtField]; [txtField release]; } } This works fine and the UITextField covers the cell. When i run this with 3.2 sdk or on the iPad the UITextField isn't aligned properly to the left, overlapping the cell and i have to use a UITextField width of 270 instead of 280 UITextField *txtField = [[UITextField alloc] initWithFrame:CGRectMake(0, 0, 270, 24)]; It seems something is wrong the pixel ratio. How can this be fixed? Is there a way to determine the version of os the device has ( 3.1.2, 3.1.3, 3.2 or maybe even the 4.0) or can it be done another way? Thank you Teo

    Read the article

  • Function parameters evaluation order: is undefined behaviour if we pass reference?

    - by bolov
    This is undefined behaviour: void feedMeValue(int x, int a) { cout << x << " " << a << endl; } int main() { int a = 2; int &ra = a; feedMeValue(ra = 3, a); return 0; } because depending on what parameter gets evaluated first we could call (3, 2) or (3, 3). However this: void feedMeReference(int x, int const &ref) { cout << x << " " << ref << endl; } int main() { int a = 2; int &ra = a; feedMeReference(ra = 3, a); return 0; } will always output 3 3 since the second parameter is a reference and all parameters have been evaluated before the function call, so even if the second parameter is evaluated before of after ra = 3, the function received a reference to a wich will have a value of 2 or 3 at the time of the evaluation, but will always have the value 3 at the time of the function call. Is the second example UB? It is important to know because the compiler is free to do anything if he detects undefined behaviour, even if I know it would always yield the same results. *Note: I think that feedMeReference(a = 3, a) is the exact same situation as feedMeReference(ra = 3, a). However it seems not everybody agrees, in the addition to having 2 completely different answers.

    Read the article

  • Cakephp, an elegant solution to quantities?

    - by Smickie
    Hi, I have a shopping cart system in Cakephp, this table has all your usual maguffins: user_ids, product_ids, option_lists ect. It also has quantity. I currently have some awful nested loops to check if the record is the same as any in there, if so add one to the quantity. If not add a new cart item. This loop has to check associated list items and product options, so it goes quite deep. What I'm wondering is if there is a more elegant way of checking to see if two cart items in a database are similar (everything except for quantity). Cheers!

    Read the article

  • Click behaviour - Difference in IE and FF ?!

    - by OlliD
    Hey folks, i just came to the conclusion that a project i am currently working on might have a "logical" error in functionality. Currently I'am using server technology with PHP/MySQL and JQuery. Within the page there's a normal link reference with tag <a href="contentpage?page=xxx">next step</a> The pain point now seems to be the given jquery click event on the same element. The intension was to save the (current) content of the page (- form elements) via another php script using the php session command. For any reason, IE can handle the click event of Jquery right before executing the standard html command, that reloads the current page again with the new page parameter. By using FF the behaviour is different. I assume, that FF first execute the html command and afterwards execute the javascript code which handles the click event. Therefore the resultset here is wrong respectivly empty. My question now is whether you made the same experience and how you handled / wordarrounded this problem. I'd be thankful fur any of your tips or further feedback. Maybe you also have a solution on how to rethink about the current architecture. Regards, Oliver

    Read the article

  • string s; &s+1; Legal? UB?

    - by John Dibling
    Consider the following code: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myAry[] = { "Mary", "had", "a", "Little", "Lamb" }; const size_t numStrs = sizeof(myStr)/sizeof(myAry[0]); vector<string> myVec(&myAry[0], &myAry[numStrs]); copy( myVec.begin(), myVec.end(), ostream_iterator<string>(cout, " ")); return 0; } Of interest here is &myAry[numStrs]: numStrs is equal to 5, so &myAry[numStrs] points to something that doesn't exist; the sixth element in the array. There is another example of this in the above code: myVec.end(), which points to one-past-the-end of the vector myVec. It's perfecly legal to take the address of this element that doesn't exist. We know the size of string, so we know where the address of the 6th element of a C-style array of strings must point to. So long as we only evaluate this pointer and never dereference it, we're fine. We can even compare it to other pointers for equality. The STL does this all the time in algorithms that act on a range of iterators. The end() iterator points past the end, and the loops keep looping while a counter != end(). So now consider this: #include <cstdlib> #include <iostream> #include <string> #include <vector> #include <algorithm> using namespace std; int main() { string myStr = "Mary"; string* myPtr = &myStr; vector<string> myVec2(myPtr, &myPtr[1]); copy( myVec2.begin(), myVec2.end(), ostream_iterator<string>(cout, " ")); return 0; } Is this code legal and well-defined? It is legal and well-defined to take the address of an array element past the end, as in &myAry[numStrs], so should it be legal and well-defined to pretend that myPtr is also an array?

    Read the article

  • AIX specific socket programming query

    - by kumar_m_kiran
    Hi All, Question 1 From SUSE man pages, I get the below details for socket connect options If the initiating socket is connection-mode, then connect() shall attempt to establish a connection to the address specified by the address argument. If the connection cannot be established immediately and O_NONBLOCK is not set for the file descriptor for the socket, connect() shall block for up to an unspecified timeout interval until the connection is established. If the timeout interval expires before the connection is established, connect() shall fail and the connection attempt shall be aborted. If connect() is interrupted by a signal that is caught while blocked waiting to establish a connection, connect() shall fail and set errno to [EINTR], but the connection request shall not be aborted, and the connection shall be established asynchronously. Question : Is the above contents valid for AIX OS (especially the connection time-out, timed wait ...etc)?Because I do not see it in AIX man pages (5.1 and 5.3) Question 2 I have a client socket whose attributes are a. SO_RCVTIMEO ,SO_SNDTIMEO are set for 5 seconds. b. AF_INET and SOCK_STREAM. c. SO_LINGER with linger on and time is 5 seconds. d. SO_REUSEADDR is set. Note that the client socket is not O_NONBLOCK. Question : Now since O_NONBLOCK is not set and SO_RCVTIMEO and SO_SNDTIMEO is set for 5 seconds, does it mean a. connect in NON Blocking or Blocking? b. If blocking, is it timed blocking or "infinite" time blocking? c. If it is infinite, How do I establish a "connect" system call which is O_BLOCKING with timeout to t secs. Sorry if the questions are be very naive. Thanks in advance for your input.

    Read the article

  • Undefined behaviour with non-virtual destructors - is it a real-world issue?

    - by Roddy
    Consider the following code: class A { public: A() {} ~A() {} }; class B: public A { B() {} ~B() {} }; A* b = new B; delete b; // undefined behaviour My understanding is that the C++ standard says that deleting b is undefined behaviour - ie, anything could happen. But, in the real world, my experience is that ~A() is always invoked, and the memory is correctly freed. if B introduces any class members with their own destructors, they won't get invoked, but I'm only interested in the simple kind of case above, where inheritance is used maybe to fix a bug in one class method for which source code is unavailable. Obviously this isn't going to be what you want in non-trivial cases, but it is at least consistent. Are you aware of any C++ implementation where the above does NOT happen, for the code shown?

    Read the article

  • Is a safe accumulator really this complicated?

    - by Martin
    I'm trying to write an accumulator that is well behaved given unconstrained inputs. This seems to not be trivial and requires some pretty strict planning. Is it really this hard? int naive_accumulator(unsigned int max, unsigned int *accumulator, unsigned int amount) { if(*accumulator + amount >= max) return 1; // could overflow *accumulator += max; // could overflow return 0; } int safe_accumulator(unsigned int max, unsigned int *accumulator, unsigned int amount) { // if amount >= max, then certainly *accumulator + amount >= max if(amount >= max) { return 1; } // based on the comparison above, max - amount is defined // but *accumulator + amount might not be if(*accumulator >= max - amount) { return 1; } // based on the comparison above, *accumulator + amount is defined // and *accumulator + amount < max *accumulator += amount; return 0; }

    Read the article

facebook twitter digg google delicious technorati stumbleupon myspace wordpress linkedin gmail igoogle windows live tumblr viadeo yahoo buzz yahoo mail yahoo bookmarks favorites email print

< Previous Page | 18 19 20 21 22 23 24 25 26 27 28 29  | Next Page >