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• Is PThread a good choice for multi-platorm C/C++ multi-threading program?

  - by RogerV

  Been doing mostly Java and smattering of .NET for last five years and haven't written any significant C or C++ during that time. So have been away from that scene for a while. If I want to write a C or C++ program today that does some multi-threading and is source code portable across Windows, Mac OS X, and Linux/Unix - is PThread a good choice? The C or C++ code won't be doing any GUI, so won't need to worry with any of that. For the Windows platform, I don't want to bring a lot of Unix baggage, though, in terms of unix emulation runtime libraries. Would prefer a PThread API for Windows that is a thin-as-possible wrapper over existing Windows threading APIs. ADDENDUM EDIT: Am leaning toward going with boost:thread - I also want to be able to use C++ try/catch exception handling too. And even though my program will be rather minimal and not particularly OOPish, I like to encapsulate using class and namespace - as opposed to C disembodied functions.

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• How to access constant defined in child class?

  - by kavoir.com

  I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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• Multithreaded SDL error in C++

  - by wyatt

  I'm building a program in C++, using SDL, and am occasionally receiving this error: * glibc detected * ./assistant: double free or corruption (!prev) It's difficult to replicate, so I can't find exactly what's causing it, but I just added a second thread to the program, and neither thread run on its own seems to cause the error. The threads don't share any variables, though they both run the functions SDL_BlitSurface and SDL_Flip. Could running these concurrently throw up such an error, or am I barking up the wrong tree? If this is the cause, should I simply throw a mutex around all SDL calls? Thanks

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• C++: Where can I define the body for a private function?

  - by Martijn Courteaux

  Hi, I have a header like this (header guards not shown): class GameSystem { public: GameSystem(Game *pcGame); virtual ~GameSystem(); void Setup(); private: void InitGame(); void RunGame(); void ExitGame(); Game *m_pcGame; /* Properties */ int m_nWidth; int m_nHeight; int m_nFps; bool m_bFullscreen; }; Where can I define the body for InitGame(), RunGame() and ExitGame()? Can I define it in my .cpp file? If so, how? Or am I obliged to make their body in my .h file? I'm using Eclipse and I began typing: void GameSystem:: and then he doesn't suggest the private functions.

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• Initializing a array after declaration

  - by robUK

  Hello, gcc 4.4.3 c89 I have the following code as a sample of what I am trying to do. I don't know the actual size of the array, until I enter the function. However, I don't think I can set the array size after I have declared it. I need it global as some other functions will need to access the device names. Many thanks for any suggestions, /* global */ char *devices_names[]; void fill_devices(size_t num_devices) { devices_names[num_devices]; /* start filling */ }

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• Why does the assignment operator return a value and not a reference?

  - by Nick Lowman

  I saw the example below explained on this site and thought both answers would be 20 and not the 10 that is returned. He wrote that both the comma and assignment returns a value, not a reference. I don't quite understand what that means. I understand it in relation to passing variables into functions or methods i.e primitive types are passed in by value and objects by reference but I'm not sure how it applies in this case. I also understand about context and the value of 'this' (after help from stackoverflow) but I thought in both cases I would still be invoking it as a method, foo.bar() which would mean foo is the context but it seems both result in a function call bar(). Why is that and what does it all mean? var x = 10; var foo = { x: 20, bar: function () {return this.x;} }; (foo.bar = foo.bar)();//returns 10 (foo.bar, foo.bar)();//returns 10

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• Add a custom class name to Wordpress body tag?

  - by Scott B

  I'd like to place a directive in my theme's functions.php file which appends a classname to the wordpress body tag. Is there a built-in API method for this? For example, my body tag code is... <body <?php if(function_exists("body_class") && !is_404()){body_class();} else echo 'class="page default"'?>> And it results in the following being written to the body tag (depending on the context in which the page is presented (page, post, logged-in, etc) <body class="home blog logged-in"> Depending on the child theme I'm using at the time, I want it to be... <body class="home blog logged-in mychildthemename">

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• Is pthread_spin_trylock safe inside of sigsegv handler of multithreaded application?

  - by TWMouton

  I am trying to implement a handler that on SIGSEGV will collect some information such as process-id, thread-id and a backtrace and write this information to a file/pipe/socket. The problem lies in that there is the (probably pretty high) possibility that if one thread experienced a SIGSEGV that the others will shortly follow. If two threads happen to make it to the bit of code where they're writing their report out at the same time then they'll interleave their writing (to the same file). I know that I should only be using async-signal-safe functions as detailed in signal(7) I also have seen at least two cases here and video linked in top answer here where others have used pthread_spin_trylock to get around this problem. Is this a safe way to prevent the above problem?

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• is there a flag "M_FAST" in FreeBSD kernel for Malloc Call ?

  - by KaluSingh Gabbar

  if you know there is one, can you let me know what its for ? if not please say so : ) thanks. Signature : void * malloc(unsigned long size, struct malloc_type type, int flags); for example. other flags are... M_ZERO Causes the allocated memory to be set to all zeros. M_WAITOK Indicates that it is OK to wait for resources. If the request cannot be immediately fulfilled, the current process is put to sleep to wait for resources to be released by other processes. The malloc(), realloc(), and reallocf() functions cannot return NULL if M_WAITOK is specified.** This is the root of my confusion EDIT: The clarification for M_FAST is made in my answer below.

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• What is the smallest Windows header I can #include to define DWORD?

  - by j_random_hacker

  I have a small header file of my own which declares a couple of functions, one of which has a return type of DWORD. I'm reluctant to drag in windows.h just to get the official definition of this type since that file is huge, and my header will be used in a number of source modules that don't otherwise need it. Of course, in practice I know that DWORD is just unsigned int, but I'd prefer the more hygienic approach of including an official header file if possible. On this page it says that DWORD is defined in windef.h, but unfortunately including just this small file directly leads to compilation errors -- apparently it expects to be included by other headers. (Also, the fact that my file is a header file also means I can't just declare WIN32_LEAN_AND_MEAN, since the source file that #includes my file might need this to be left undefined.) Any ideas? I know it's not the end of the world -- I can just continue to #include <windows.h> -- but thought someone might have a better idea!

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• How to change the value of progressbar in C#?

  - by shekhar

  Hi, I want to add an progress bar into my C# based application. I would like to know what is the good way of updating its value at particular events? My problem is, I have single function in UI which does all the processing.This function in turn calls many more functions, creates objects, updates database, etc. (basically performs all the work) and returns values in an output file. I have access to that function only. So in this how to update the progressbar's value at the end of each step? What is the best practice for this kind of situation? What is the good way to keep UI logic and business logic seperate? I want to avoid writting progressbar related code in my library code. Please suggest some solution. Thanks and Regards,

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• Emacs and Long Shell Commands

  - by darrint

  Is there a way to run a shell command, have the output show up in a new buffer and have that output show up incrementally? Eshell and other emacs terminal emulators do a find job of this but I see no way to script them. What I'd like to do is write little elisp functions to do stuff like run unit tests, etc. and watch the output trickle into a buffer. The elisp function shell-command is close to what I want but it shows all the output at once when the process finishes.

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• c++ compilation error

  - by clamp

  hello, i got a compile error which i do not understand. i have a h/cpp file combination that does not contain a class but just defines some utility functions. when i try to use a struct that is defined in another class i get the error: error C2027: use of undefined type so, stripped down to the problem, the h file looks like this namespace A { void foo(B::C::SStruct const & Var); } the definition of SStruct is in a class which is in another h-file, that is of course included. namespace B { Class C { struct SStruct { }; } } what am i missing here? thanks!

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• Change notification in CouchDB when a field is set

  - by PartlyCloudy

  Hi, I'm trying to get notifications in a CouchDB change poll as soon as pre-defined field is set or changed. I've already had a look at filters that can be used for filtering change events(db/_changes?filter=myfilter). However, I've not yet found a way to include this temporal information, because you can only get the current version of the document in this filter functions. Is there any possibility to create such a filter? If it does not work, I could export my field to a separate database and the only poll for changes in that db, but I'd prefer to keep together my data for obvious reasons. Thanks in advance!

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• Function to set an auth_token

  - by john mossel

  In my form I have a hidden field: <input type="hidden" name="auth_token" value="<?php echo $auth_token; ?>"> This value is also stored in a session and a variable: $_SESSION['auth_token'] = hash('sha256', rand() . time() . $_SERVER['HTTP_USER_AGENT']); # TODO: put this in a function $auth_token = $_SESSION['auth_token']; When the form is submitted the two values are compared. It's a basic form token. Should this be made into two functions or just one when refactored? set_form_token() and get_form_token(), get_form_token() returning the session value, then I can compare it in my main code. What is the proper way of doing this?

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• undefined reference to "func" when complied with GCC

  - by hotlemontea

  I implement a link list in two files in linklist.h and linklist.c, and I call some functions defined in linklist.h in main function of main.c. linklist.h is included in both linklist.c and main.c. When I compile this program by GCC with Makefile, the error named "undefined reference to xxx" occurs. I think my Makefile is written correctly as below. So what is the possible reason for this linking error CC=gcc CFLAGS= -g -O2 TARGET=target OBJECTS=main.o linklist.o TARGET: $(OBJECTS) $(CC) $(CFLAGS) $(OBJECTS) -o $(TARGET) clean: rm target $(OBJECTS) main.o:linklist.h linklist.o:linklist.h

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• What is the precedence of characters when sorting in MySQL, PHP, or just in general?

  - by FireCoding

  Question: Where can I find the precedence of characters when sorting in MySQL, PHP, or just in general on Linux and Windows OS? For example, everybody knows that a comes before b when performing an ascending sort on a string in MySQL. But what about other characters? Does the dollar-sign $ come before asterisk * ? Does a space come before an exclamation-mark? etc... What dictates the sort order? Does it use underlying ascii / UTF-8 values? Is it different for different technologies? Technologies to consider: Databases - MySQL / SQL / SQLite / Oracle / etc Programming languages (for string-sorting functions) - PHP / Javascript / ASP.NET / Visual C# / Python / Ruby / Objective C OS (i.e., sorting files by filename) - Windows / Linux / MacOS / iOS / Android

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• Should I convert data arrays to objects in PHP in a CouchDB/Ajax app?

  - by karlthorwald

  I find myself converting between array and object all the time in PHP application that uses couchDB and Ajax. Of course I am also converting objects to JSON and back (for sometimes couchdb but mostly Ajax), but this is not so much disturbing my workflow. At the present I have php objects that are returned by the CouchDB modules I use and on the other hand I have the old habbit to return arrays like array("error"="not found","data"=$dataObj) from my functions. This leads to a mixed occurence of real php objects and nested arrays and I cast with (object) or (array) if necessary. The worst thing is that I know more or less by heart what a function returns, but not what type (array or object), so I often run into type errors. My plan is now to always cast arrays to objects before returning from a function. Of course this implies a lot of refactoring. Is this the right way to go? What about the conversion overhead? Other ideas or tips?

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• MySQL LEFT JOIN issue with three WHERE statements

  - by jhat

  I am building a note taking app for myself with tag filtering functions, but am having an issue when trying to grab notes with the tags. The tag filter needs to use AND not IN, because it will help better narrow down what I am looking for. My tables are configured like this: + notes note_id | note_title | note_uid + tags tag_id | tag_title + notes_tags nt_id | nt_note_id | nt_tag_id The notes_tags table keeps track of all notes' tags. I am not worried about returning any information about tags, so here is an example LEFT JOIN I am using currently to only get notes with only 1 tag. SELECT * FROM notes_tags LEFT JOIN notes ON note_id = nt_note_id WHERE note_uid IN ( 1 ) AND nt_tag_id = 10 This query runs perfect, it grabs all of the notes with that single tag. However, I am having issues "pinpointing" my notes using a query like this: SELECT * FROM notes_tags LEFT JOIN notes ON note_id = nt_note_id WHERE note_uid IN ( 1 ) AND nt_tag_id = 10 AND nt_tag_id = 11 What am I doing wrong with the syntax?

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• How should I use try...except while defining a function?

  - by SpawnCxy

  Hi all, I find I've been confused by the problem that when I needn't to use try..except.For last few days it was used in almost every function I defined which I think maybe a bad practice.For example: class mongodb(object): def getRecords(self,tname,conditions=''): try: col = eval("self.db.%s" %tname) recs = col.find(condition) return recs except Exception,e: #here make some error log with e.message What I thought is ,exceptions may be raised everywhere and I have to use try to get them. And my question is,is it a good practice to use it everywhere when defining functions?If not are there any principles for it?Help would be appreciated! Regards

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• how to use replace_regex_copy() from boost::algorithm library?

  - by Vincenzo

  This is my code: #include <string> #include <boost/algorithm/string/regex.hpp> string f(const string& s) { using namespace boost::algorithm; return replace_regex_copy(s, "\\w", "?"); } This is what compiler says: no matching function for call to ‘replace_regex_copy(const std::basic_string<char, std::char_traits<char>, std::allocator<char> >&, std::string, std::string) The link to the library: http://www.boost.org/doc/libs/1_43_0/doc/html/boost/algorithm/replace_regex_copy.html Could anyone please help? Thanks! ps. Boost library is in place, since other functions from it work fine.

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• PHP: Remove blank line before text

  - by Bailey

  Occasionally, my email-to-support-ticket system catches an extra line break before the message itself, thus my messages look like this: " Hello. I have been wondering if y..." What can I use to get rid of that line before the text? It is on random occasion due to email providers and the way they format their emails using mime. I have already tried the trim functions but no luck. (Yes, I also tried ltrim) Once processed it should look like: "Hello. I have been wondering if y..."

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• Looking for a standard way to manage documents in a WPF application

  - by user322383

  Hi! I'm writing a WPF application that uses one document at a time. Is there any standard way to implement the management of the current document? What I mean are the following functions: New document: if there are not saved changes in the current document, a dialog box opens ('Do you want to save changes to {0}?') with Yes/No/Cancel buttons. If Cancel is hit, the operation stops. Open document: same dialog box as at new document, and an Open dialog opens after Save document: if the current document hasn't been saved, a Save dialog opens Save as: you can imagine... So, is there anything standard in the .NET framework like this or do I have to manually implement it?

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• Changing the way widgets are rendered/displayed in a form on the template

  - by user334017

  I have a form with a few other embedded forms and some various widgets. The widgets are all saved in an array $form['elements'] and for some of them, I want to display labels and things, but for others I only want to display the basic rendering. foreach($form['elements'] as $elem) echo $elem->render(); this displays everything about the widget. The way it is right now, I couldn't for example call $elem['..'] because the different subforms appear in a random order and have different variable names. I assume I could still put some checks in the template, but it seems easier to fix this in the widget class, like override one of the render functions or something. How would I go about doing this or do you have any links that could help me understand how do do this? on a side note, one of my widgets is the sfWidgetFormChoice and I have no clue where it actually renders or how renderer_classes work

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• PHP Datediff days involved

  - by user3549835

  I need to know how many days are involved in a date diff. \For example: <? $start = new DateTime('2014-06-29 14:00:00'); $ende = new DateTime('2014-07-02 05:45:00'); $diff = $start->diff($ende); echo $diff->format('%R'); echo $diff->days; ?> The above code echos +2 My desired result would be 4, because the 29th, 30th, 1st and 2nd of July are "touched". I have no idea to achieve that with the given functions. Coding a day-subtraction seems to bean open door for errors.

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