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  • Does C++ require a destructor call for each placement new?

    - by Josh Haberman
    I understand that placement new calls are usually matched with explicit calls to the destructor. My question is: if I have no need for a destructor (no code to put there, and no member variables that have destructors) can I safely skip the explicit destructor call? Here is my use case: I want to write C++ bindings for a C API. In the C API many objects are accessible only by pointer. Instead of creating a wrapper object that contains a single pointer (which is wasteful and semantically confusing). I want to use placement new to construct an object at the address of the C object. The C++ object will do nothing in its constructor or destructor, and its methods will do nothing but delegate to the C methods. The C++ object will contain no virtual methods. I have two parts to this question. Is there any reason why this idea will not work in practice on any production compiler? Does this technically violate the C++ language spec?

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  • Why is volatile not considered useful in multithreaded C or C++ programming?

    - by Michael E
    As demonstrated in this answer I recently posted, I seem to be confused about the utility (or lack thereof) of volatile in multi-threaded programming contexts. My understanding is this: any time a variable may be changed outside the flow of control of a piece of code accessing it, that variable should be declared to be volatile. Signal handlers, I/O registers, and variables modified by another thread all constitute such situations. So, if you have a global int foo, and foo is read by one thread and set atomically by another thread (probably using an appropriate machine instruction), the reading thread sees this situation in the same way it sees a variable tweaked by a signal handler or modified by an external hardware condition and thus foo should be declared volatile (or, for multithreaded situations, accessed with memory-fenced load, which is probably a better a solution). How and where am I wrong?

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  • JSP Component Creation

    - by jboyd
    When creating JSP pages one thing that I'd often like is the ability to do something like this: <jsp:include page="fancystoryrenderer.jsp" value="${aStoryObjectInMyModel}/> ... fancystoryrenderer.jsp <div id="fancymainbody"> ... ${theStory.title} ... </div> The main important characteristics of this is that I can reuse the same component on the same JSP page in different places without having to copy paste the component and give the story variables different names, notice that the story is called "theStory" in the JSP and not "aStoryObjectInMyModel", the linkage between our model has been broken by the view, which is a good thing in this case How do you do this?

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  • C string program

    - by mrblippy
    Hi, i have been given a task to do ar school that must read three strings in, store the third string in dynamically allocated memory and print out the last 4 letters of the first word alphabetically. Here is the program i have so far but the strings are all stored in different variables, making them hard to sort. if anyone could give me a hand and help me finish this program i would be very grateful. thanks #include <stdio.h> #include <stdlib.h> #include <string.h> int main() { char word1[101]; char word2[101]; char* word3; char buffer[101]; scanf("%s", word1); scanf("%s", word2); scanf("%s", buffer); word3 = (char *) malloc(strlen(buffer)+1); strcpy(word3, buffer); return 0; }

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  • Using Components.utils.import in a firefox extension

    - by jamesatha
    I am trying to create some global variables in a firefox extension. In my content folder, I have two javascript files: 1) Main JS file that holds the functions for the different events, etc 2) A file that stores only an object with the pieces of state I want to maintain. Also, I set the array EXPORTED_SYMBOLS. I am having issues with the following line found in my main JS file: Components.utils.import("resource:///globalVariables.js"); When it is at the top of the file, nothing seems to work. If I move it into the function where I need the variable, the rest of my code works, but the function with this line does nothing. Any advice that would help me with this problem would be great. Thanks

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  • php array regular expressions

    - by bell
    I am using regular expressions in php to match postcodes found in a string. The results are being returned as an array, I was wondering if there is any way to assign variables to each of the results, something like $postcode1 = first match found $postcode2 = second match found here is my code $html = "some text here bt123ab and another postcode bt112cd"; preg_match_all("/([a-zA-Z]{2})([0-9]{2,3})([a-zA-Z]{2})/", $html, $matches, PREG_SET_ORDER); foreach ($matches as $val) { echo $val[0]; } I am very new to regular expressions and php, forgive me if this is a stupid question. Thanks in advance

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  • Do I need to install Glassfish?

    - by Ayusman
    Hi, I am new to glassfish server. i have a question on glassfish usage: can I just use glassfish like a tomcat server without needing an installation? where in, I just take a folder containing glassfish folders, jars etc... dump it in a folder location setup a few environment variables and it runs.. just like tomcat? is it possible with glassfish? also does glassfish installation does any other background things like creating registry entries etc other than creating the glassfish folder structure? TIA Ayusman

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  • Manage bad_alloc exception in C++ construtor

    - by Jimmy zhang
    I have Java experience and recently am doing some C++ coding. My question is that if I have class A, in which I have to instantiate class B and class C as two of the member variables of A. If in the constructor of A, should I assume that allocations of class B and C never fail, and handle the bad allocation exception in the destructor of A? If I don't make that assumption, meaning that I add some try catch block to catch bad_alloc of class B and class C, then if the allocation exception occurs, should I do clean up in the constructor of A? What are the recommended practices? If "new" generates a bad allocation, what value does the pointer carry?

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  • Fully automated MS SQL Restore

    - by hasen j
    I'm not very fluent with MS-SQL commands. I need a script to restore a database from a .bak file and move the logical_data and logical_log files to a specific path. I can do: restore filelistonly from disk='D:\backups\my_backup.bak' This will give me a result set with a column LogicalName, next I need to use the logical names from the result set in the restore command: restore database my_db_name from disk='d:\backups\my_backups.bak' with file=1, move 'logical_data_file' to 'd:\data\mydb.mdf', move 'logical_log_file' to 'd:\data\mylog.ldf' How do I capture the logical names from the first result set into variables that can be supplied to the "move" command? I think the solution might be trivial, but I'm pretty new to mssql.

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  • Cache images provided through script

    - by Wim Haanstra
    I have a script, which by using several querystring variables provides an image. I am also using URL rewriting within IIS 7.5. So images have an URL like this: http://mydomain/pictures/ajfhajkfhal/44/thumb.jpg or http://mydomain/pictures/ajfhajkfhal/44.jpg This is rewritten to: http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44&thumb=thumb.jpg or http://mydomain/Picture.aspx?group=ajfhajkfhal&id=44 I added caching rules to IIS to cache JPG images when they are requested. This works with my images that are REAL images on the disk. When images are provided through the script, they are somehow always requested through the script, without being cached. The images do not change that often, so if the cache at least is being kept for 30 minutes (or until file change) that would be best. I am using .NET/C# 4.0 for my website. I tried setting several cache options in C#, but I cant seem to find how to cache these images (client-side), while my static images are cached properly.

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  • PHP split string into integer element and string

    - by David19801
    Hello, I have a string say: Order_num = "0982asdlkj" How can I split that into the 2 variables, with the number element and then another variable with the letter element in php? The number element can be any length from 1 to 4 say and the letter element fills the rest to make every order_num 10 characters long in total. I have found the php explode function...but don't know how to make it in my case because the number of numbers is between 1 and 4 and the letters are random after that, so no way to split at a particular letter. Please help as specifically as possible!

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  • What is the difference between an object's scope and it's context in javascript?

    - by DKinzer
    In the vernacular, scope and context have a lot in common. Which is why I get confused when I read references to both, such as in the quote below from an article on closures: Scope refers to where variables and functions are accessible, and in what context it is being executed. (@robertnyman) As far as I can tell, context is just a reference to an object. Can someone please explain what exactly is context, as used, for instance, in the jQuery syntax, $(selector, context). And is an object's scope the same at it's context?

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  • What is good practice for writing web applications that control daemons (and their config files)

    - by Jones R
    Can someone suggest some basic advice on dealing with web applications that interact with configuration files like httpd.conf, bind zone files, etc. I understand that it's bad practice, in fact very dangerous to allow arbitrary execution of code without fully validating it and so on. But say you are tasked to write a small app that allows one to add vhosts to an apache configuration. Do you have your code execute with full privileges, do you write future variables into a database and have a cron job (with full privileges) execute a script that pulls the vars from the database and throws them into a template config file, etc. Some thoughts & contributions on this issue would be appreciated. tl;dr - how can you securely write a web app to update/create entries in a config file like apache's httpd.conf, etc.

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  • Override properties block when including a psake script in an other psake script

    - by DanceAlot
    I am new to psake and I have this issue: I have 2 psake scripts: (1): base_tasks.ps1: properties{ $a = "hello" $b = "hi" } task One{ Write-Host $a } (2): install.ps1 Include .\base_tasks.ps1 properties{ $a = "Goodbye" $b = "Adjeu" } task default -depends One Now, is it possible to override the properties and variables from file 1? I want to use file 1 as "base tasks" and use the tasks in the install.ps1 and override the properties. Or do I have to do that an other way? I will invoke install.ps1 and use my $a and $b from install.ps1. DanceAlot

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  • Three boolean values saved in one tinyint

    - by Casper
    Hello, probably a simple question but I seem to be suffering from programmer's block. :) I have three boolean values: A, B, and C. I would like to save the state combination as an unsigned tinyint (max 255) into a database and be able to derive the states from the saved integer. Even though there are only a limited number of combinations, I would like to avoid hard-coding each state combination to a specific value (something like if A=true and B=true has the value 1). I tried to assign values to the variables so (A=1, B=2, C=3) and then adding, but I can't differentiate between A and B being true from i.e. only C being true. I am stumped but pretty sure that it is possible. Thanks

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  • Display calculating result in the same page

    - by garcon1986
    Hello, I have a table in my php code. In the second column of the table, normally it displays "---", and after i click the submit button, it will display the calculating result in the same page. For example, <table> <tr><td>1</td><td>---</td></tr> <tr><td>2</td><td>---</td></tr> <tr><td>3</td><td>---</td></tr> </table> And in the same page, it should receive the variables $var1 = $_POST['variable1']; I'm not sure which way to use, ajax or javascript or just css? Do you have any ideas? Thanks

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  • What is on the 68000 stack when classic MacOS enters a program?

    - by John Källén
    I'm trying to understand an old classic Mac application's entry point. I've disassembled the first CODE resource (not CODE#0, which is the jump table). The code refers to some variables off the stack: a word at 0004(A7), an array of long words of starting at 000C(A7) whose length is the value at 0004(A7), and a final long word beyond that array that seems to be a pointer to a character string. The array of long words looks like strings at first glance, so it looks superficially like we're dealing with an (int argc, char ** argv) situation, except the "argv" array is inline in the stack frame. What should a program be expecting on its stack / registers when it first gets called by the Mac OS?

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  • functions in assembler

    - by stupid_idiot
    hi, i have philosophised about the purpose of stack a little bit and after some coding i figured out what is it's strength. The only thing that lies in my stomache is how does it work with functions? I tried to make some easy function for adding two numbers using universal registers but I suppose that's not how does it work in C for example.. where are all the parameters, local variables and where is the result stored? how would you rewrite this to assembler?(how would compiler for C rewrite it?) int function(int a, int &b, int *c){ return a*(b++)+(*c); } i know this example kinda sucks.. but this way i can understand all the possibilities

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  • Sort Java List/Map by order in which items are in an XML File

    - by Brandon Smith
    Hello everyone, What I'm looking to do is to sorta a Java List or Map in the order the items are in a XML File. For Example I have a list of function names as so: functionOne functionThree functionTwo The XML File looks like this: <xml> <function>functionOne</function> <function>functionTwo</function> <function>functionThree</function> </xml> So I would like to sort the list so the function names are as so: functionOne functionTwo functionThree Now Im trying to do this for Variables as well, so there are around 500+ unique 'items'. Does anyone have any idea how I can go about doing this? Now for the file that determines that sort order doesn't have to be XML it just what I use the most, it can be anything that can get the job done. Thanks in advance for your time.

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  • How to handle dependency files in a cross-platform manner?

    - by Brian Knoblauch
    I'm working on updating an old app. It has some dependency files that live in the same directory as the app. Obviously this broke when Windows Vista came out (since it violates the API and Vista/7 now enforce that (XP didn't)). Ideally, I'd like to avoid hardcoding anything into the app for just Windows. I can live with that if I have to though. I've already been down that path with pulling the APPDATA and LOCALAPPDATA environment variables, but that doesn't help any since they just give you the current user area... I need these to live somewhere accessible for all users, and I'd like to obey the Windows API expectations that they go into the all user appdata area. Suggestions?

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  • ios - how do I concatinate strings to create a url?

    - by GeekedOut
    I am trying to make a url by first collecting the parameters, and then in one statement creating the actual url. Here is what I am trying to do: NSString *urlString = @"http://www.some_login_url.com?email=%@&password=%@"; NSString *email = self.email.text; NSString *password = self.password.text; NSString *url_to_send = [NSString stringWithFormat:@"%@%@", urlString , email , password]; So what I wanted to do was replace the @ symbols with the values in the variables, but instead the second variable just got appended to the end of the string. How would I change the last line so I could put the right parameters in their correct spots? Thanks!!

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  • is right to implement a business logic in the type binding DI framwork?

    - by Martino
    public IRedirect FactoryStrategyRedirect() { if (_PasswordExpired) { return _UpdatePasswordRedirectorFactory.Create(); } else { return _DefaultRedirectorFactory.Create(); } } This strategy factory method can be replaced with type binding and when clause: Bind<IRedirect>.To<UpdatePasswordRedirector>.When(c=> c.kernel.get<SomeContext>().PasswordExpired()) Bind<IRedirect>.To<DefaultRedirector>.When(c=> not c.kernel.get<SomeContext>().PasswordExpired()) I wonder which of the two approaches is the more correct. What are the pros and cons. Especially in the case in which the logic is more complex with more variables to test and more concrete classes to return. is right to implement a business logic in the binding?

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  • SQL Server (TSQL) - Is it possible to EXEC statements in parallel?

    - by Investor5555
    SQL Server 2008 R2 Here is a simplified example: EXECUTE sp_executesql N'PRINT ''1st '' + convert(varchar, getdate(), 126) WAITFOR DELAY ''000:00:10''' EXECUTE sp_executesql N'PRINT ''2nd '' + convert(varchar, getdate(), 126)' The first statement will print the date and delay 10 seconds before proceeding. The second statement should print immediately. The way T-SQL works, the 2nd statement won't be evaluated until the first completes. If I copy and paste it to a new query window, it will execute immediately. The issue is that I have other, more complex things going on, with variables that need to be passed to both procedures. What I am trying to do is: Get a record Lock it for a period of time while it is locked, execute some other statements against this record and the table itself Perhaps there is a way to dynamically create a couple of jobs? Anyway, I am looking for a simple way to do this without having to manually PRINT statements and copy/paste to another session. Is there a way to EXEC without wait / in parallel?

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  • Prevent Erroneous Property Assignment

    - by Gordon
    Porting android applications to iphone applications always gives me the following pattern that I accidentally create: - (void) myFunc:(id)prop { self.property = property; } Which instead should be: - (void) myFunc:(id)prop { self.property = prop; } This always causes my program to quietly break because property gets reset to its existing value rather than being set to the new value, 'prop'. I cannot name the parameter 'prop' to 'property' since the compile complains that the parameter masks the instance variables visibility. Is there a good way to avoid this situation? There are no compiler warnings. Is there a way to make xcode prevent this? I cannot see very many situations where you would set a property to the value of its underlying instance variable (maybe to trigger a KVO binding?), but I don't see myself doing that in majority of cases. I understand the above code is synthetic and should be done with @synthesize, but I am just using it as a simplified example to illustrate my point.

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  • PHP export to text file - Only saving first line.

    - by wertz8090
    I'm trying to export some extracted $_POST information into a text file, however my code is only capturing the first variable and ignoring the rest. I'm saving the information to the text file in this manner: $values = "First Name: $fName\r\n"; $values .= "Last Name: $lName\r\n"; $values .= "Address: $address\r\n"; etc. This is the code I use to write to the text file: $fp = @fopen("person.data", "w") or die("Couldn't open person.data for writing!"); $numBytes = @fwrite($fp, $values) or die("Couldn't write values to file!"); @fclose($fp); Any ideas on why it would only save the first $values ($fName) variable but not the rest of them? It actually saves the first part of the $values string for all of them (so I see Last Name:, Address:, etc. on separate lines in the text file) but the called variables $lName and $address do not appear.

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