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• How to 'hide' spurious "declared but never used" warnings?

  - by Roddy

  I'm using the C++Builder compiler which has a minor bug that certain static const items from system header files can cause spurious "xyzzy is declared but never used" warnings. I'm trying to get my code 100% warning free, so want a way of masking these particular warnings (note - but not by simply turning off the warning!) Also, I can't modify the header files. I need a way of 'faking' the use of the items, preferably without even knowing their type. As an example, adding this function to my .cpp modules fixes warnings for these four items, but it seems a bit 'ad-hoc'. Is there a better and preferably self-documenting way of doing this? static int fakeUse() { return OneHour + OneMinute + OneSecond + OneMillisecond; }

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• C++ class is not being included properly.

  - by ravloony

  Hello all, I have a problem which is either something I have completely failed to understand, or very strange. It's probably the first one, but I have spent the whole afternoon googling with no success, so here goes... I have a class called Schedule, which has as a member a vector of Room. However, when I compile using cmake, or even by hand, I get the following: In file included from schedule.cpp:1: schedule.h:13: error: ‘Room’ was not declared in this scope schedule.h:13: error: template argument 1 is invalid schedule.h:13: error: template argument 2 is invalid schedule.cpp: In constructor ‘Schedule::Schedule(int, int, int)’: schedule.cpp:12: error: ‘Room’ was not declared in this scope schedule.cpp:12: error: expected ‘;’ before ‘r’ schedule.cpp:13: error: request for member ‘push_back’ in ‘((Schedule*)this)->Schedule::_sched’, which is of non-class type ‘int’ schedule.cpp:13: error: ‘r’ was not declared in this scope Here are the relevant bits of code: #include <vector> #include "room.h" class Schedule { private: std::vector<Room> _sched; //line 13 int _ndays; int _nrooms; int _ntslots; public: Schedule(); ~Schedule(); Schedule(int nrooms, int ndays, int ntslots); }; Schedule::Schedule(int nrooms, int ndays, int ntslots):_ndays(ndays), _nrooms(nrooms),_ntslots(ntslots) { for (int i=0; i<nrooms;i++) { Room r(ndays,ntslots); _sched.push_back(r); } } In theory, g++ should compile a class before the one that includes it. There are no circular dependencies here, it's all straightforward stuff. I am completely stumped on this one, which is what leads me to believe that I must be missing something. :-D

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• Why am I getting this warning about my app delegate and CLLocationManageDelegate?

  - by Dan Ray

  Observe this perfectly simple UIViewController subclass method: -(IBAction)launchSearch { OffersSearchController *search = [[OffersSearchController alloc] initWithNibName:@"OffersSearchView" bundle:nil]; EverWondrAppDelegate *del = [UIApplication sharedApplication].delegate; [del.navigationController pushViewController:search animated:YES]; [search release]; } On the line where I get *del, I am getting a compiler warning that reads, Type 'id <UIApplicationDelegate>' does not conform to the 'CLLocationManagerDelegate' protocol. In fact, my app delegate DOES conform to that protocol, AND what I'm doing here has nothing at all to do with that. So what's up with that message? Secondary question: sometimes I can get to my navigationController via self.navigationController, and sometimes I can't, and have to go to my app delegate's property to get it like I'm doing here. Any hint about why that is would be very useful.

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• How to learn to program C the right way

  - by sfactor

  i have been programming in C/C++ for my academic courses a lot and was under the impression i had a pretty good grasp of it. but lately i had to work in a bluetooth application that had a server and client implementation in a Linux box and an embedded system. i learned bluez bluetooth API, socket/network programming and coded it. however i ran into a lot of problems with memory leaks and segmentation faults and other memory related errors along the way.as the code grew more complex i all but lost control of the pointers and threads and sockets. this got me wondering that i had a lot to learn that they didn't say in the basic C/C++ books. so i wanted to ask for the resources that are available that'll help be code better in a professional way in C/C++ .especially for the Linux/Mac environment (gcc compiler).

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• remote function with pthread

  - by user311130

  Hi all, I wrote some code in c, using pthread (I configured the linker and compiler in eclipse IDE first). #include <pthread.h> #include "starter.h" #include "UI.h" Page* MM; Page* Disk; PCB* all_pcb_array; void* display_prompt(void *id){ printf("Hello111\n"); return NULL; } int main(int argc, char** argv) { printf("Hello\n"); pthread_t *thread = (pthread_t*) malloc (sizeof(pthread_t)); pthread_create(thread, NULL, display_prompt, NULL); printf("Hello\n"); return 1; } that works fine. However, when I move display_prompt to UI.h no "Hello111 " output is printed. anyone know how to solve that? Elad

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• Using type hints in Clojure for Java return values

  - by mikera

  I'm working on some Java / Clojure interoperability and came across a reflection warning for the following code: (defn load-image [resource-name] (javax.imageio.ImageIO/read (.getResource (class javax.imageio.ImageIO) resource-name))) => Reflection warning, clojure/repl.clj:37 - reference to field read can't be resolved. I'm surprised at this because getResource always returns a URL and I would therefore expect the compiler to use the appropriate static method in javax.imageio.ImageIO/read. The code works fine BTW so it is clearly finding the right method at run time. So two questions: Why is this returning a reflection warning? What type hint do I need to fix this?

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• What about race condition in multithreaded reading?

  - by themoob

  Hi, According to an article on IBM.com, "a race condition is a situation in which two or more threads or processes are reading or writing some shared data, and the final result depends on the timing of how the threads are scheduled. Race conditions can lead to unpredictable results and subtle program bugs." . Although the article concerns Java, I have in general been taught the same definition. As far as I know, simple operation of reading from RAM is composed of setting the states of specific input lines (address, read etc.) and reading the states of output lines. This is an operation that obviously cannot be executed simultaneously by two devices and has to be serialized. Now let's suppose we have a situation when a couple of threads access an object in memory. In theory, this access should be serialized in order to prevent race conditions. But e.g. the readers/writers algorithm assumes that an arbitrary number of readers can use the shared memory at the same time. So, the question is: does one have to implement an exclusive lock for read when using multithreading (in WinAPI e.g.)? If not, why? Where is this control implemented - OS, hardware? Best regards, Kuba

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• Bulletin board - Database optimisation

  - by andrew

  This question is a follow on from this Question The project and problem The project I am currently working on is a bulletin board for a large non-profit organisation. The bulletin board will be used to allow inter-office communication within the organisation. I am building the application and have been having trouble extracting the results that I need from my database because I don't think it is properly normalized and because of limitations in my knowledge of relational database theory and mysql. I would appreciate input into the design of the board in general and in particular, ways that the database structure can be improved to facilitate efficient queries and help me develop this application and future application faster Business Logic The bulletin board will be used in the following way Posting bulletins and responses to bulletins Employees or 'users' in offices around the country will be able to post messages to the bulletin board.Bulletins must be posted to a location and categorised- i'll call these "bulletins". Users will be able to post any number of replies to any one bulletin and users will be able to reply to their own bulletin - i'll call these 'replies'. Rating bulletins and replies Users will be able to either 'like' or 'dislike' a bulletin or a reply and the total number of likes or dislikes will be shown for each bulletin or reply. Viewing the bulletin board and responses Bulletins can be displayed chronologically. Users can sort bulletins chronologically or chronologically by the latest reply to that bulletin(let me know if you need more explanation) When a particular bulletin is selected, replies to that bulletin will be displayed chronologically @PerformanceDBA - edited 10:34 est 28/12/10I have begun implementing the data model. I assume that the 6th data model is the physical model because it contains the associative tables. I am going to post any questions that I have below. I will put up a database dump once I am done. I will then put up a list of all the queries that I need to run on the database and begin writing them. I hope you had a good Christmas. I'm in Canada and there's snow! Implementation of Physical model

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• Error in my OO Generics design. How do I workaround it?

  - by John

  I get "E2511 Type parameter 'T' must be a class type" on the third class. type TSomeClass=class end; ParentParentClass<T>=class end; ParentClass<T: class> = class(ParentParentClass<T>) end; ChildClass<T: TSomeClass> = class(ParentClass<T>) end; I'm trying to write a lite Generic Array wrapper for any data type(ParentParentClass) ,but because I'm unable to free type idenitifiers( if T is TObject then Tobject(T).Free) , I created the second class, which is useful for class types, so I can free the objects. The third class is where I use my wrapper, but the compiler throws that error. How do I make it compile?

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• Preventing symbols from being stripped in IBM Visual Age C/C++ for AIX

  - by smountcastle

  I'm building a shared library which I dynamically load (using dlopen) into my AIX application using IBM's VisualAge C/C++ compiler. Unfortunately, it appears to be stripping out necessary symbols: rtld: 0712-002 fatal error: exiting. rtld: 0712-001 Symbol setVersion__Q2_3CIF17VersionReporterFRCQ2_3std12basic_stringXTcTQ2_3std11char_traitsXTc_TQ2_3std9allocatorXTc__ was referenced from module ./object/AIX-6.1-ppc/plugins/plugin.so(), but a runtime definition of the symbol was not found. Both the shared library and the application which loads the shared library compile/link against the static library which contains the VersionReporter mentioned in the error message. To link the shared library I'm using these options: -bM:SRE -bnoentry -bexpall To link the application, I'm using this option: -brtl Is there an option I can use to prevent this symbol from being stripped in the application? I've tried using -nogc as stated in the IBM docs, but that causes the shared library to be in an invalid format or the application to fail to link (depending on which one I use it with).

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• Visual C++ 2010 solution-wide macros with parameters

  - by OregonGhost

  I'm trying to compile some source code with Visual C++ 2010 Express. The code was written for GCC, and contains attributes like this: struct something { ... } __attribute__((packed)); Since this is not standard C++ syntax, Visual C++ doesn't recognize it. With this macro prior to the struct declaration, it works fine: #define __attribute__(p) But I don't want to alter the files. I created a new property sheet (GccCompat), and went to Preprocessor Definitions, and added the macro, like this: __attribute__(p) or like this: __attribute__(p)= But it doesn't work. It's simply not called. If I define just __attribute__ (without parameters) in the same location, the macro is correctly defined. Note that the command line that is generated looks fine (the macros with parameters are passed exactly the same as the ones without), but the compiler seems to ignore it. So, how can I globally define my macro with a parameter?

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• Java FileFilter

  - by Mr CooL

  public class DocFilter extends FileFilter { public boolean accept(File f) { if (f.isDirectory()) { return true; } String extension = Utils.getExtension(f); if (extension != null) { if (extension.equals(Utils.doc) || extension.equals(Utils.docx) ) { return true; } else { return false; } } return false; } //The description of this filter public String getDescription() { return "Just Document Files"; } } Netbeans compiler warned with the error, "No interface expected here" for above code Anyone has idea what was the problem?? I tried changing the 'extends' to 'implements', however, it didn't seem to work that way. and when I changed to implements, the following code cannot work, chooser.addChoosableFileFilter(new DocFilter()); and with this error, "method addChoosableFileFilter in class javax.swing.JFileChooser cannot be applied to given types required: javax.swing.filechooser.FileFilter" Can anyone help on this? Thanks..

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• ObjC internals. Why my duck typing attempt failed?

  - by Piotr Czapla

  I've tried to use id to create duck typing in objective-c. The concept looks fine in theory but failed in practice. I was unable to use any parameters in my methods. The methods were called but parameters were wrong. I was getting BAD_ACESS for objects and random values for primitives. I've attached a simple example below. The question: Does any one knows why the methods parameters are wrong? What is happening under the hood of the objective-c? Note: I'm interest in the details. I know how to make the example below work. An example: I've created a simple class Test that is passed to an other class using property id test. @implementation Test - (void) aSampleMethodWithFloat:(float) f andInt: (int) i { NSLog(@"Parameters: %f, %i\n", f, i); } @end Then in the class the following loop is executed: for (float f=0.0f; f < 100.0f ; f += 0.3f) { [self.test aSampleMethodWithOneFloatParameter: f]; // warning: no method found. } Here is the output that I'm getting. As you can see the method was called but the parameters were wrong. Parameters: 0.000000, 0 Parameters: -0.000000, 1069128089 Parameters: -0.000000, 1070176665 Parameters: 2.000000, 1070805811 Parameters: -0.000000, 1071225241 Parameters: 0.000000, 1071644672 Parameters: 2.000000, 1071854387 Parameters: 36893488147419103232.000000, 1072064102 Parameters: -0.000000, 1072273817 Parameters: -36893488147419103232.000000, 1072483532

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• Confusion about Nullable<T> constraints

  - by n535

  Greetings everybody. I am sorry, if this was already asked before (searched in vain) or is really very simple, but i just can't get it. The MSDN definition of a Nullable type, states, that it is defined in a following manner: [SerializableAttribute] public struct Nullable<T> where T : struct, new() So the question is quite straightforward: How is this definition possible? Or this is just a typo? Every value type already has a default constructor. Indeed, when i try to compile something like this, the compiler reasonably says, that it is illegal to apply both constraints at the same time, because the second one is implicitly included in a first one. Thanks in advance.

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• c++ Using const in a copy constructor?

  - by Anton

  I have never written copy constructor, so in order to avoid pain i wanted to know if what i have coded is legit. It compiles but i am not sure that it works as a copy constructor should. Also do i have to use const in the copy constructor or i can simply drop it. (What i dont like about const is that the compiler cries if i use some non const functions). //EditNode.h class EditNode { explicit EditNode(QString elementName); EditNode(const EditNode &src); } //EditNodeContainer.h class EditNodeContainer : public EditNode { explicit EditNodeContainer(QString elementName); EditNodeContainer(const EditNodeContainer &src); } //EditNodeContainer.cpp EditNodeContainer::EditNodeContainer(QString elementName):EditNode(elementName) { } //This seems to compile but not sure if it works EditNodeContainer::EditNodeContainer(const EditNodeContainer &src):EditNode(src) { } //the idea whould be to do something like this EditNodeContainer *container1 = new EditNodeContainer("c1"); EditNodeContainer *copyContainer = new EditNodeContainer(container1);

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• Cross-platform SOA framework

  - by ByteMR

  I'm looking for a good cross-platform SOA framework that preferably works with several programming languages like C++, Python, and C#. I recently learned about Thrift, but that doesn't seem to work with MSVC from the documentation I've read and requires the use of Cygwin or MinGW to even compile the Thrift compiler. Does Thrift work with MSVC and if not, are there any alternatives that would meet my needs? Such as being able to generate C# and Python bindings and work on Linux, Mac, and Windows. Any suggestions would be greatly appreciated!

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• ASP.NET UserControl not defined?

  - by BryanG

  I've just inherited an app that utilizes usercontrols in a couple ways which I'm not too familiar with. The problem I have right now is that when I attempt to publish this code base, I get a few errors which boil down to where some referenced usercontrols are not defined. Here's an example of one line: Private clientControl As New ASP.usercontrols_clientcontrol_ascx This is a tab strip usercontrol which references other usercontrols to dynamically create the tabs. Now, on the surface I get what is going on here...but the compiler is not accepting this. This tab strip usercontrol is in the root of the project, and the other usercontrols are in a sub folder. error BC30002: Type 'ASP.usercontrols_clientcontrol_ascx' is not defined. I'm sure this is 101 stuff here, but the build works and the publish fails. Any direction would be appreciated.

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• Error : Implementation for method missing (Delphi Prism)

  - by Ilya

  I wrote my method: LangChange type MainForm = partial class(System.Windows.Forms.Form) private ... method LangChange(); protected method Dispose(disposing: Boolean); override; public constructor; end; implementation ... method LangChange(); begin ... end; However,I have an error Error 1 (PE33) Implementation for method "Compiler.MainForm.LangChange" missing What is wrong?Help please!

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• How should rules for Aggregate Roots be enforced?

  - by MylesRip

  While searching the web, I came across a list of rules from Eric Evans' book that should be enforced for aggregates: The root Entity has global identity and is ultimately responsible for checking invariants Root Entities have global identity. Entities inside the boundary have local identity, unique only within the Aggregate. Nothing outside the Aggregate boundary can hold a reference to anything inside, except to the root Entity. The root Entity can hand references to the internal Entities to other objects, but they can only use them transiently (within a single method or block). Only Aggregate Roots can be obtained directly with database queries. Everything else must be done through traversal. Objects within the Aggregate can hold references to other Aggregate roots. A delete operation must remove everything within the Aggregate boundary all at once When a change to any object within the Aggregate boundary is committed, all invariants of the whole Aggregate must be satisfied. This all seems fine in theory, but I don't see how these rules would be enforced in the real world. Take rule 3 for example. Once the root entity has given an exteral object a reference to an internal entity, what's to keep that external object from holding on to the reference beyond the single method or block? (If the enforcement of this is platform-specific, I would be interested in knowing how this would be enforced within a C#/.NET/NHibernate environment.)

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• How to initialize an std::string using ""?

  - by Mohsin

  I'm facing problems with initializing a std::string variable using "" (i.e. an empty string). It's causing strange behavior in code that was previously working. Is the following statement wrong? std::string operationalReason = ""; When I use the following code everything works fine: std::string operationalReason; operationalReason.clear(); I believe that string literals are stored in a separate memory location that is compiler-dependent. Could the problem I'm seeing actually be indicating a corruption of that storage? If so, it would get hidden by my usage of the clear() function. Thanks.

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• Why aren't operator conversions implicitly called for templated functions? (C++)

  - by John Gordon

  I have the following code: template <class T> struct pointer { operator pointer<const T>() const; }; void f(pointer<const float>); template <typename U> void tf(pointer<const float>); void g() { pointer<float> ptr; f(ptr); tf(ptr); } When I compile the code with gcc 4.3.3 I get a message (aaa.cc:17: error: no matching function for call to ‘tf(pointer<float>&)’) indicating that the compiler called 'operator pointer<const T>' for the non-templated function f(), but didn't for the templated function tf(). Why and is there any workaround short of overloading tf() with a const and non-const version? Thanks in advance for any help.

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• Are returned locals automatically xvalues

  - by mark

  Following on from a comment I made on this: passing std::vector to constructor and move semantics Is the std::move necessary in the following code, to ensure that the returned value is a xvalue? std::vector<string> buildVector() { std::vector<string> local; // .... build a vector return std::move(local); } It is my understanding that this is required. I have often seen this used when returning a std::unique_ptr from a function, however GManNickG made the following comment: It is my understanding that in a return statement all local variables are automatically xvalues (expiring values) and will be moved, but I'm unsure if that only applies to the returned object itself. So OP should go ahead and put that in there until I'm more confident it shouldn't have to be. :) Can anyone clarify if the std::move is necessary? Is the behaviour compiler dependent?

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• Force external function to be const

  - by vanna

  Here is my problem. I made a class with a member function declared as const that uses an external function that I cannot modify (declared in someone else's code) and that is not declared const. More precisely Someone else's code class B { public: void foo(); }; My code class A : public B { public: void bar() const { this->foo(); } }; I know that for member data we can force const-correctness by using mutable or const_cast. How can I 'hack' foo such that my compiler understands that I would like to use it as if it was const even if it is not declared in someone else's code ?

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• Stop CDATA tags from being output-escaped when writing to XML in C#

  - by Smallgods

  We're creating a system outputting some data to an XML schema. Some of the fields in this schema need their formatting preserved, as it will be parsed by the end system into potentially a Word doc layout. To do this we're using <![CDATA[Some formatted text]]> tags inside of the App.Config file, then putting that into an appropriate property field in a xsd.exe generated class from our schema. Ideally the formatting wouldn't be out problem, but unfortunately thats just how the system is going. The App.Config section looks as follows: <header> <![CDATA[Some sample formatted data]]> </header> The data assignment looks as follows: HeaderSection header = ConfigurationManager.GetSection("header") as HeaderSection; report.header = "<[CDATA[" + header.Header + "]]>"; Finally, the Xml output is handled as follows: xs = new XmlSerializer(typeof(report)); fs = new FileStream (reportLocation, FileMode.Create); xs.Serialize(fs, report); fs.Flush(); fs.Close(); This should in theory produce in the final Xml a section that has information with CDATA tags around it. However, the angled brackets are being converted into &lt; and &gt; I've looked at ways of disabling Outout Escaping, but so far can only find references to XSLT sheets. I've also tried @"<[CDATA[" with the strings, but again no luck. Any help would be appreciated!

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• Optional structural typing possibilty in C++ or anyother language?

  - by ambhai

  In C++ how to tell compiler that Ogre::Vector3 IS_SAME_AS SomeOtherLIB::Vector3 ? I feel that.. in languages like c++ which are not structural typed but there are cases when it makes sense. Normally as game developer when working with 4+ libraries that provide sort or their own Vector3 implementation. The code is littered with ToOgre, ToThis, ToThat conversion function. Thats a lot of Float3 copying around which should not happen on first place. Is in C++ or any other languages where we dont have to convert (copying) from one type to another which is essentially the samething. But any solution in C++ as most of the good gamedevs libs are for c/c++.

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