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• Problems adding static library QT project

  - by Smek

  I have problems adding a static library to my Qt project. I have two project one is my static library and the other one is a Qt GUI project. As I add all classes to my GUI project as c++ or header files everything works just fine but I want this to be in a separate library. When I select the option to add a library I check External library then I select the .a file I have build and the folder where my header files can be found because I am working on a Mac I select Mac as the target platform. Then I click continue and then done. macx: LIBS += -L$$PWD/../../MyLib/build-MyLib-Desktop_Qt_5_2_1_clang_64bit-Debug/ -lMyLib INCLUDEPATH += $$PWD/../../MyLib/build-MyLib-Desktop_Qt_5_2_1_clang_64bit-Debug/include DEPENDPATH += $$PWD/../../MyLib/build-MyLib-Desktop_Qt_5_2_1_clang_64bit-Debug/include macx: PRE_TARGETDEPS += $$PWD/../../MyLib/build-MyLib-Desktop_Qt_5_2_1_clang_64bit-Debug/libMyLib.a When I build my GUI project I get the following error: The process "/usr/bin/make" exited with code 2. Can anyone tell me what the problem can be and how to resolve the problem? Thanks

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• static const double in c++

  - by Crystal

  Is this the proper way to use a static const variable? In my top level class (Shape) #ifndef SHAPE_H #define SHAPE_H class Shape { public: static const double pi; private: double originX; double originY; }; const double Shape::pi = 3.14159265; #endif And then later in a class that extends Shape, I use Shape::pi. I get a linker error. I moved the const double Shape::pi = 3.14... to the Shape.cpp file and my program then compiles. Why does that happen? thanks.

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• Java static method parameters

  - by Blitzkr1eg

  Why does the following code return 100 100 1 1 1 and not 100 1 1 1 1 ? public class Hotel { private int roomNr; public Hotel(int roomNr) { this.roomNr = roomNr; } public int getRoomNr() { return this.roomNr; } static Hotel doStuff(Hotel hotel) { hotel = new Hotel(1); return hotel; } public static void main(String args[]) { Hotel h1 = new Hotel(100); System.out.print(h1.getRoomNr() + " "); Hotel h2 = doStuff(h1); System.out.print(h1.getRoomNr() + " "); System.out.print(h2.getRoomNr() + " "); h1 = doStuff(h2); System.out.print(h1.getRoomNr() + " "); System.out.print(h2.getRoomNr() + " "); } } Why does it appear to pass Hotel by-value to doStuff() ?

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• undefined reference to static member variable

  - by Max

  Hi. I have this class that has a static member. it is also a base class for several other classes in my program. Here's its header file: #ifndef YARL_OBJECT_HPP #define YARL_OBJECT_HPP namespace yarlObject { class YarlObject { // Member Variables private: static int nextID; // keeps track of the next ID number to be used int ID; // the identifier for a specific object // Member Functions public: YarlObject(): ID(++nextID) {} virtual ~YarlObject() {} int getID() const {return ID;} }; } #endif and here's its implementation file. #include "YarlObject.hpp" namespace yarlObject { int YarlObject::nextID = 0; } I'm using g++, and it returns three undefined reference to 'yarlObject::YarlObject::nextID linker errors. If I change the ++nextID phrase in the constructor to just nextID, then I only get one error, and if I change it to 1, then it links correctly. I imagine it's something simple, but what's going on?

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• Defining private static class member

  - by mnn

  class B { /* ... */ }; class A { public: A() { obj = NULL; } private: static B* obj; }; However this produces huge mass of linker errors that symbol obj is unresolved. What's the "correct" way to have such private static class member without these linker errors? Edit: I tried this: B *A::obj = NULL; but I got about same amount of linker errors however this time about already defining A::obj. (LNK2005). Also I get LNK4006 warnings, also about A::obj

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• Getting count() of class static array

  - by xylar

  Is it possible to get the count of a class defined static array? For example: class Model_Example { const VALUE_1 = 1; const VALUE_2 = 2; const VALUE_3 = 3; public static $value_array = array( self::VALUE_1 => 'boing', self::VALUE_2 => 'boingboing', self::VALUE_3 => 'boingboingboing', ); public function countit() { // count number $total = count(self::$value_array ); echo ': '; die($total); } } At the moment calling the countit() method returns :

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• C++ - defining static const integer members in class definition

  - by HighCommander4

  My understanding is that C++ allows static const members to be defined inside a class so long as it's an integer type. Why, then, does the following code give me a linker error? #include <algorithm> #include <iostream> class test { public: static const int N = 10; }; int main() { std::cout << test::N << "\n"; std::min(9, test::N); } The error I get is: test.cpp:(.text+0x130): undefined reference to `test::N' collect2: ld returned 1 exit status Interestingly, if I comment out the call to std::min, the code compiles and links just fine (even though test::N is also referenced on the previous line). Any idea as to what's going on? My compiler is gcc 4.4 on Linux.

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• background image or color for a static box in vc++

  - by shashank saket

  anyone knows how we can set an image or color for the background in a static box in vc++

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• Pass form object value to static method

  - by jrubengb

  Hi, I need to take a form object value and pass it into a static method: public void SetCalendarStartSafe(DateTime startDateSafe) { startDateSafe = calendarStart.Value; } private static DataTable GetData() { frmMain frm = new frmMain(); DateTime startDate = new frmMain(); frm.SetCalendarStartSafe(startDate); } However I keep getting today's current date whenever I try this approach, even if the specified calendar date on the form is different. How can I can the user-specified calendar date from the original frmMain object? Thanks in advance for any guidance.

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• Simulating aspects of static-typing in a duck-typed language

  - by Mike

  In my current job I'm building a suite of Perl scripts that depend heavily on objects. (using Perl's bless() on a Hash to get as close to OO as possible) Now, for lack of a better way of putting this, most programmers at my company aren't very smart. Worse, they don't like reading documentation and seem to have a problem understanding other people's code. Cowboy coding is the game here. Whenever they encounter a problem and try to fix it, they come up with a horrendous solution that actually solves nothing and usually makes it worse. This results in me, frankly, not trusting them with code written in duck typed language. As an example, I see too many problems with them not getting an explicit error for misusing objects. For instance, if type A has member foo, and they do something like, instance->goo, they aren't going to see the problem immediately. It will return a null/undefined value, and they will probably waste an hour finding the cause. Then end up changing something else because they didn't properly identify the original problem. So I'm brainstorming for a way to keep my scripting language (its rapid development is an advantage) but give an explicit error message when an an object isn't used properly. I realize that since there isn't a compile stage or static typing, the error will have to be at run time. I'm fine with this, so long as the user gets a very explicit notice saying "this object doesn't have X" As part of my solution, I don't want it to be required that they check if a method/variable exists before trying to use it. Even though my work is in Perl, I think this can be language agnostic.

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• Using Unit Tests While Developing Static Libraries in Obj-C

  - by macinjosh

  I'm developing a static library in Obj-C for a CocoaTouch project. I've added unit testing to my Xcode project by using the built in OCUnit framework. I can run tests successfully upon building the project and everything looks good. However I'm a little confused about something. Part of what the static library does is to connect to a URL and download the resource there. I constructed a test case that invokes the method that creates a connection and ensures the connection is successful. However when my tests run a connection is never made to my testing web server (where the connection is set to go). It seems my code is not actually being ran when the tests happen? Also, I am doing some NSLog calls in the unit tests and the code they run, but I never see those. I'm new to unit testing so I'm obviously not fully grasping what is going on here. Can anyone help me out here? P.S. By the way these are "Logical Tests" as Apple calls them so they are not linked against the library, instead the implementation files are included in the testing target.

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• Static variable not initialized

  - by Simon Linder

  Hi all, I've got a strange problem with a static variable that is obviously not initialized as it should be. I have a huge project that runs with Windows and Linux. As the Linux developer doesn't have this problem I would suggest that this is some kind of wired Visual Studio stuff. Header file class MyClass { // some other stuff here ... private: static AnotherClass* const Default_; }; CPP file AnotherClass* const Default_(new AnotherClass("")); MyClass(AnotherClass* const var) { assert(Default_); ... } Problem is that Default_is always NULL. I also tried a breakpoint at the initialization of that variable but I cannot catch it. There is a similar problem in another class. CPP file std::string const MyClass::MyString_ ("someText"); MyClass::MyClass() { assert(MyString_ != ""); ... } In this case MyString_is always empty. So again not initialized. Does anyone have an idea about that? Is this a Visual Studio settings problem? Cheers Simon

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• Is it normal for C++ static initialization to appear twice in the same backtrace?

  - by Joseph Garvin

  I'm trying to debug a C++ program compiled with GCC that freezes at startup. GCC mutex protects function's static local variables, and it appears that waiting to acquire such a lock is why it freezes. How this happens is rather confusing. First module A's static initialization occurs (there are __static_init functions GCC invokes that are visible in the backtrace), which calls a function Foo(), that has a static local variable. The static local variable is an object who's constructor calls through several layers of functions, then suddenly the backtrace has a few ??'s, and then it's is in the static initialization of a second module B (the __static functions occur all over again), which then calls Foo(), but since Foo() never returned the first time the mutex on the local static variable is still set, and it locks. How can one static init trigger another? My first theory was shared libraries -- that module A would be calling some function in module B that would cause module B to load, thus triggering B's static init, but that doesn't appear to be the case. Module A doesn't use module B at all. So I have a second (and horrifying) guess. Say that: Module A uses some templated function or a function in a templated class, e.g. foo<int>::bar() Module B also uses foo<int>::bar() Module A doesn't depend on module B at all At link time, the linker has two instances of foo<int>::bar(), but this is OK because template functions are marked as weak symbols... At runtime, module A calls foo<int>::bar, and the static init of module B is triggered, even though module B doesn't depend on module A! Why? Because the linker decided to go with module B's instance of foo::bar instead of module A's instance at link time. Is this particular scenario valid? Or should one module's static init never trigger static init in another module?

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• Nested namespaces, correct static library design issues

  - by PeterK

  Hello all, I'm currently in the process of developing a fairly large static library which will be used by some tools when it's finished. Now since this project is somewhat larger than anything i've been involved in so far, I realized its time to think of a good structure for the project. Using namespaces is one of those logical steps. My current approach is to divide the library into parts (which are not standalone, but their purpose calls for such a separation). I have a 'core' part which now just holds some very common typedefs and constants (used by many different parts of the library). Other parts are for example some 'utils' (hash etc.), file i/o and so on. Each of these parts has its own namespace. I have nearly finished the 'utils' part and realized that my approach probably is not the best. The problem (if we want to call it so) is that in the 'utils' namespace i need something from the 'core' namespace which results in including the core header files and many using directives. So i began to think that this probably is not a good thing and should be changed somehow. My first idea is to use nested namespaces as to have something like core::utils. Since this will require some heavy refactoring i want to ask here first. What do you think? How would you handle this? Or more generally: How to correctly design a static library in terms of namespaces and code organization? If there are some guidelines or articles about it, please mentoin them too. Thanks. Note: i'm quite sure that there are more good approaches than just one. Feel free to post your ideas, suggestions etc. Since i'm designing this library i want it to be really good. The goal is to make it as clean and FAST as possible. The only problem is that i will have to integrate a LOT of existing code and refactor it, which will really be a painful process (sigh) - thats why good structure is so important)

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• Static Libraries on iPhone device

  - by Akusete

  I have two projects, a Cocoa iPhone application and a static library which it uses. I've tested it successfully on the iPhone simulator, but when I try to deploy it to my iPhone device I get (symbol not found) link errors. If I remove the dependancy of the library the project builds/runs fine. I have made sure all the build settings are set to iPhoneOS not the simulator. Im sure its something simple, but has anyone run into similar problems moving from iPhone simulator to device? --EDIT: I have managed to create new projects (one for the application and one for the static library), and successfully get them to run on the iPhone or simulator. But I have a very strange problem... for each specific project I cannot get it working for BOTH the device and the simulator... I have double checked the build settings, made sure the libraries that are being references are for the matching build settings (I believe) but I cannot resolve these linking errors. I think I must be doing something very wrong... all the apple documentation says 'its super simple - one click' but this is giving me a lot of problems. This is probably something to do with xCode build settings, but I cannot seem to understand why selecting the different build platforms and rebuilding the libraries does not work.

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• Mac OS X and static boost libs -> std::string fail

  - by Ionic

  Hi all, I'm experiencing some very weird problems with static boost libraries under Mac OS X 10.6.6. The error message is main(78485) malloc: *** error for object 0x1000e0b20: pointer being freed was not allocated *** set a breakpoint in malloc_error_break to debug [1] 78485 abort (core dumped) and a tiny bit of example code which will trigger this problem: #define BOOST_FILESYSTEM_VERSION 3 #include <boost/filesystem.hpp> #include <iostream> int main (int argc, char **argv) { std::cout << boost::filesystem::current_path ().string () << '\n'; } This problem always occurs when linking the static boost libraries into the binary. Linking dynamically will work fine, though. I've seen various reports for quite a similar OS X bug with GCC 4.2 and the _GLIBCXX_DEBUG macro set, but this one seems even more generic, as I'm neither using XCode, nor setting the macro (even undefining it does not help. I tried it just to make sure it's really not related to this problem.) Does anybody have any pointers to why this is happening or even maybe a solution (rather than using the dynamic library workaround)? Best regards, Mihai

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• PHP static objects giving a fatal error

  - by Webbo

  I have the following PHP code; <?php component_customer_init(); component_customer_go(); function component_customer_init() { $customer = Customer::getInstance(); $customer->set(1); } function component_customer_go() { $customer = Customer::getInstance(); $customer->get(); } class Customer { public $id; static $class = false; static function getInstance() { if(self::$class == false) { self::$class = new Customer; } else { return self::$class; } } public function set($id) { $this->id = $id; } public function get() { print $this->id; } } ?> I get the following error; Fatal error: Call to a member function set() on a non-object in ....../classes/customer.php on line 9 Can anyone tell me why I get this error? I know this code might look strange, but it's based on a component system that I'm writing for a CMS. The aim is to be able to replace HTML tags in the template e.g.; <!-- component:customer-login --> with; <?php component_customer_login(); ?> I also need to call pre-render methods of the "Customer" class to validate forms before output is made etc. If anyone can think of a better way, please let me know but in the first instance, I'd like to know why I get the "Fatal error" mentioned above. Cheers

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• Initializing static pointer in templated class.

  - by Anthony

  This is difficult for me to formulate in a Google query (at least one that gives me what I'm looking for) so I've had some trouble finding an answer. I'm sure I'm not the first to ask though. Consider a class like so: template < class T > class MyClass { private: static T staticObject; static T * staticPointerObject; }; ... template < class T > T MyClass<T>::staticObject; // <-- works ... template < class T > T * MyClass<T>::staticPointerObject = NULL; // <-- cannot find symbol staticPointerObject. I am having trouble figuring out why I cannot successfully create that pointer object. Edit: The above code is all specified in the header, and the issue I mentioned is an error in the link step, so it is not finding the specific symbol.

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• Static Analyzer says I have a leak....why?

  - by Walter

  I think this code should be fine but Static Analyzer doesn't like it. I can't figure out why and was hoping that someone could help me understand. The code works fine, the analyzer result just bugs me. Coin *tempCoin = [[Coin alloc] initalize]; self.myCoin = tempCoin; [tempCoin release]; Coin is a generic NSObject and it has an initalize method. myCoin is a property of the current view and is of type Coin. I assume it is telling me I am leaking tempCoin. In my view's .h I have set myCoin as a property with nonatomic,retain. I've tried to autorelease the code as well as this normal release but Static Analyzer continues to say: 1. Method returns an Objective-C object with a +1 retain count (owning reference) 2. Object allocated on line 97 is no longer referenced after this point and has a retain count of +1 (object leaked) Line 97 is the first line that I show.

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• Converting formCollection array to objects in the controller

  - by bergin

  in my view I have several [n].propertyName array fields I want to turn the formCollection fields into objects myobject[n].propertyName when it goes to the controller. so for example, the context: View: foreach (var item in Model.SSSubjobs.AsEnumerable()) <%: Html.Hidden("["+c+"].sssj_id", item.sssj_id ) %> <%: Html.Hidden("["+c+"].order_id", item.order_id ) %> <%: Html.TextBox("["+c+"].farm", item.farm %> <%: Html.TextBox("["+c+"].field", item.field %> c++; Controller: I want to take the above [0].sssj_id and turn into sssj[0].sssj_id or a list of sssj objects My first idea was to look in the form collection for things starting with "[" but I have a feeling this isnt right... this is as far as I got: public IList<SoilSamplingSubJob> extractSSSJ(FormCollection c) { IList<SoilSamplingSubJob> sssj_list=null; SoilSamplingSubJob sssj; var n=0; foreach (var key in c.AllKeys) // iterate through the formcollection { var value = c[key]; if(key.StartsWith("[")) // ie turn [0].gps_pk_chx into sssj.gps_pk_chx ??? } return sssj_list; }

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• c# Most efficient way to combine two objects

  - by Dested

  I have two objects that can be represented as an int, float, bool, or string. I need to perform an addition on these two objects with the results being the same thing c# would produce as a result. For instance 1+"Foo" would equal the string "1Foo", 2+2.5 would equal the float 5.5, and 3+3 would equal the int 6 . Currently I am using the code below but it seems like incredible overkill. Can anyone simplify or point me to some way to do this efficiently? private object Combine(object o, object o1) { float left = 0; float right = 0; bool isInt = false; string l = null; string r = null; if (o is int) { left = (int)o; isInt = true; } else if (o is float) { left = (float)o; } else if (o is bool) { l = o.ToString(); } else { l = (string)o; } if (o1 is int) { right = (int)o1; } else if (o is float) { right = (float)o1; isInt = false; } else if (o1 is bool) { r = o1.ToString(); isInt = false; } else { r = (string)o1; isInt = false; } object rr; if (l == null) { if (r == null) { rr = left + right; } else { rr = left + r; } } else { if (r == null) { rr = l + right; } else { rr = l + r; } } if (isInt) { return Convert.ToInt32(rr); } return rr; }

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• Most efficient way to combine two objects in C#

  - by Dested

  I have two objects that can be represented as an int, float, bool, or string. I need to perform an addition on these two objects with the results being the same thing c# would produce as a result. For instance 1+"Foo" would equal the string "1Foo", 2+2.5 would equal the float 5.5, and 3+3 would equal the int 6 . Currently I am using the code below but it seems like incredible overkill. Can anyone simplify or point me to some way to do this efficiently? private object Combine(object o, object o1) { float left = 0; float right = 0; bool isInt = false; string l = null; string r = null; if (o is int) { left = (int)o; isInt = true; } else if (o is float) { left = (float)o; } else if (o is bool) { l = o.ToString(); } else { l = (string)o; } if (o1 is int) { right = (int)o1; } else if (o is float) { right = (float)o1; isInt = false; } else if (o1 is bool) { r = o1.ToString(); isInt = false; } else { r = (string)o1; isInt = false; } object rr; if (l == null) { if (r == null) { rr = left + right; } else { rr = left + r; } } else { if (r == null) { rr = l + right; } else { rr = l + r; } } if (isInt) { return Convert.ToInt32(rr); } return rr; }

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• Looking for a better way to integrate a static list into a set of classes

  - by EvilTeach

  I'm trying to expand my sons interest from Warcraft 3 programming into C++ to broaden his horizons to a degree. We are planning on porting a little game that he wrote. The context goes something like this. There are Ships and Missiles, for which Ships will use Missiles and interact with them A Container exists which will hold 'a list' of ships. A Container exists which will hold 'a list' of planets. One can apply a function over all elements in the Container (for_each) Ships and Missles can be created/destroyed at any time New objects automatically insert themselves into the proper container. I cobbled a small example together to do that job, so we can talk about topics (list, templates etc) but I am not pleased with the results. #include <iostream> #include <list> using namespace std; /* Base class to hold static list in common with various object groups */ template<class T> class ObjectManager { public : ObjectManager ( void ) { cout << "Construct ObjectManager at " << this << endl; objectList.push_back(this); } virtual ~ObjectManager ( void ) { cout << "Destroy ObjectManager at " << this << endl; } void for_each ( void (*function)(T *) ) { for (objectListIter = objectList.begin(); objectListIter != objectList.end(); ++objectListIter) { (*function)((T *) *objectListIter); } } list<ObjectManager<T> *>::iterator objectListIter; static list<ObjectManager<T> *> objectList; }; /* initializer for static list */ template<class T> list<ObjectManager<T> *> ObjectManager<T>::objectList; /* A simple ship for testing */ class Ship : public ObjectManager<Ship> { public : Ship ( void ) : ObjectManager<Ship>() { cout << "Construct Ship at " << this << endl; } ~Ship ( void ) { cout << "Destroy Ship at " << this << endl; } friend ostream &operator<< ( ostream &out, const Ship &that ) { out << "I am a ship"; return out; } }; /* A simple missile for testing */ class Missile : public ObjectManager<Missile> { public : Missile ( void ) : ObjectManager<Missile>() { cout << "Construct Missile at " << this << endl; } ~Missile ( void ) { cout << "Destroy Missile at " << this << endl; } friend ostream &operator<< ( ostream &out, const Missile &that ) { out << "I am a missile"; return out; } }; /* A function suitable for the for_each function */ template <class T> void show ( T *it ) { cout << "Show: " << *it << " at " << it << endl; } int main ( void ) { /* Create dummy planets for testing */ Missile p1; Missile p2; /* Demonstrate Iterator */ p1.for_each(show); /* Create dummy ships for testing */ Ship s1; Ship s2; Ship s3; /* Demonstrate Iterator */ s1.for_each(show); return 0; } Specifically, The list is effectively embedded in each ship though the inheritance mechanism. One must have a ship, in order to access the list of ships. One must have a missile in order to be able to access the list of missiles. That feels awkward. My question boils down to "Is there a better way to do this?" Automatic object container creation Automatic object insertion Container access without requiring an object in the list to access it. I am looking for better ideas. All helpful entries get an upvote. Thanks Evil.

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• Optional Member Objects

  - by David Relihan

  Okay, so you have a load of methods sprinkled around your systems main class. So you do the right thing and refactor by creating a new class and perform move method(s) into a new class. The new class has a single responsibility and all is right with the world again: class Feature { public: Feature(){}; void doSomething(); void doSomething1(); void doSomething2(); }; So now your original class has a member variable of type object: Feature _feature; Which you will call in the main class. Now if you do this many times, you will have many member-objects in your main class. Now these features may or not be required based on configuration so in a way it's costly having all these objects that may or not be needed. Can anyone suggest a way of improving this? At the moment I plan to test in the newly created class if the feature is enabled - so the when a call is made to method I will return if it is not enabled. I could have a pointer to the object and then only call new if feature is enabled - but this means I will have to test before I call a method on it which would be potentially dangerous and not very readable. Would having an auto_ptr to the object improve things: auto_ptr<Feature> feature; Or am I still paying the cost of object invokation even though the object may\or may not be required. BTW - I don't think this is premeature optimisation - I just want to consider the possibilites.

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• Moving objects colliding when using unalligned collision avoidance (steering)

  - by James Bedford

  I'm having trouble with unaligned collision avoidance for what I think is a rare case. I have set two objects to move towards each other but with a slight offset, so one of the objects is moving slightly upwards, and one of the objects is moving slightly downwards. In my unaligned collision avoidance steering algorithm I'm finding the points on the object's forward line and the other object's forward line where these two lines are the closest. If these closest points are within a collision avoidance distance, and if the distance between them is smaller than the two radii of the two object's bounding spheres, then the objects should steer away in the appropriate direction. The problem is that for my case, the closest points on the lines are calculated to be really far away from the actual collision point. This is because the two forward lines for each object are moving away from each other as the objects pass. The problem is that because of this, no steering takes place, and the two objects partially collide. Does anyone have any suggestions as to how I can correctly calculate the point of collision? Perhaps by somehow taking into account the size of the two objects?

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