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• Duplicate Symbol Linker Error (C++ help)

  - by Vash265

  Hi. I'm learning some CSP (constraint satisfaction) theory stuff right now, and am using this library to parse XML files. I'm using Xcode as an IDE. My program compiles fine, but when it goes to link the files, I get a duplicate symbol error with the XMLParser_libxml2.hh file. My files are separated as such: A class header file that includes the XMLParser file above A class implementation file that include the class header file A main file that includes the class header file The duplicate symbol is occurring in main.o and classfile.o, but as far as I can tell, I'm not actually adding that .hh file twice. Full error: ld: duplicate symbol bool CSPXMLParser::UTF8String::to<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >(std::basic_string<char, std::char_traits<char>, std::allocator<char> >&) constin /Users/vash265/CSP/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/x86_64/dStructFill.o and /Users/vash265/CSP/Untitled/build/Untitled.build/Debug/Untitled.build/Objects-normal/x86_64/main.o Copying the implementation of the class into the main file and taking the class implementation file out of the compilation target alleviates the error, but it's a disorganized mess this way, and I'll be adding more classes very soon (and it would be nice to have them in separate files). As I've come to understand it, this is caused by the file (XMLParser_libxml2.hh) having both the class and function definition and implementation in one file (and it seems as though this might have been necessary due to the use of templates in that 'header' file). Any ideas on how to get around sticking all my class files in my main.cpp? (I've tried ifdefs, they don't work).

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• Passing a template func. as a func. ptr to an overloaded func. - is there a way to compile this code

  - by LoudNPossiblyRight

  Just a general c++ curiosity: This code below shouldn't compile because it's impossible to know which to instantiate: temp(const int&) or temp(const string&) when calling func(temp) - this part i know. What i would like to know is if there is anything i can do to the line marked PASSINGLINE to get the compiler to deduce that i want FPTR1 called and not FPTR2 ? #include<iostream> using std::cout; using std::endl; /*FPTR1*/ void func(void(*fptr)(const int&)){ fptr(1001001);} /*FPTR2*/ void func(void(*fptr)(const string&)){ fptr("1001001"); } template <typename T> void temp(const T &t){ cout << t << endl; } int main(){ /*PASSINGLINE*/ func(temp); return 0; } Thank you.

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• Netbeans C++ not finding standard libraries (Macintosh)

  - by Grue

  Hello everyone! I am trying to use Netbeans 6.7 (on a Mac) to create C++ applications. I started out with the standard "Hello World," just to test if everything was working correctly. First try std and could not be found. So I tried reinstalling the developer tools on my Mac OS X disk. After that Netbeans updated its c++ compiler info, but still cannot find std or . Odder than this XCode seems to be working with C++ perfectly fine. Any help fixing this would be greatly appreciated.

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• snprintf and Visual Studio 2010

  - by Andrew

  I'm unfortunate enough to be stuck using VS 2010 for a project, and noticed the following code still doesn't build using the non-standards compliant compiler: #include <stdio.h> #include <stdlib.h> int main (void) { char buffer[512]; snprintf(buffer, sizeof(buffer), "SomeString"); return 0; } (fails compilation with the error: C3861: 'snprintf': identifier not found) I remember this being the case way back with VS 2005 and am shocked to see it still hasn't been fixed. Does any one know if Microsoft has any plans to move their standard C libraries into the year 2010?

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• Generating random numbers in C

  - by moonstruckhorrors

  While searching for Tutorials on generating random numbers in C I found This Topic When I try to use the rand() function with parameters, I always get the random number generated 0. When I try to use the rand() function with parameters, I always get the value 41. And whenever I try to use arc4random() and random() functions, I get a LNK2019 error. Here's what I'm doing: #include <stdlib.h> int main() { int x; x = rand(6); printf("%d", x); } This code always generate 41. Where am I going wrong?? P.S. : I'm running Windows XP SP3 and using VS2010 Command Prompt as compiler. P.P.S. : Took me 15 minutes to learn how to format properly.

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• Qt compilation and stylesheet

  - by Yosko

  Each time I compile my Qt project after modifying my qss stylesheet file, the modifications aren't taken into account, unless I rebuild everything. Any idea on a workaround for this, so that I don't have to wait 5 minutes each time I change my qss ? Notes: I use Qt 4.8, and my stylsheet is declared in a resource file (qrc). EDIT: As suggested by Luca Carlon, when a qss is reference in the project through a .qrc file, the changes in the qss don't affect the qrc, and the compiler ignores it. To avoid that, I added a Custom Build Step to my project: before the qmake step! calls a .bat file without any argument the .bat contains the real command copy /b files.qrc +,,

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• mmap only needed pages of kernel buffer to user space

  - by axeoth

  See also this answer: http://stackoverflow.com/a/10770582/1284631 I need something similar, but without having to allocate a buffer: the buffer is large, in theory, but the user space program only needs to access some parts of it (it mocks some registers of a hardware). As I cannot allocate with vmalloc_user() such a large buffer (kernel 32 bit, in embedded environment, no swap...), I followed the same approach as in the quoted answer, trying to allocate only those pages that are really requested by the user space. So: I use a my_mmap() function for the device file (actually, is the .mmap field of a struct uio_info) to set up the fields of the vma, then, in the vm_area_struct's .fault field (also named my_fault()), I should return a page. except that: In the my_fault() method of vm_area_struct, I cannot obtain a page through: vmf->page=vmalloc_to_page(my_buf + (vmf->pgoff << PAGE_SHIFT)); since there is no allocated buffer: my_buf = vmalloc_user(MY_BUF_SIZE); fails with "allocation failed: out of vmalloc space - use vmalloc= to increase size." (and there is no room or swap to increase that vmalloc= parameter). So, I would need to get a page from the kernel and fill the vmf->page field. How to allocate a page (I assume that the offset of the page is known, as it is vm->pgoff). What base memory should I use instead of my_buf? PS: I also did set up the vma->flags |= VM_NORESERVE; (in the my_mmap()), but not sure if it helps. Is there any vmalloc_user_unreserved()-like function? (let's say, lazy allocation) Also, writing 1 to /proc/sys/vm/overcommit_memory and large values (eg 500) to /proc/sys/vm/overcommit_ratio before trying to my_buf=vmalloc_user(<large_size>) didn't work.

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• Eclipse RCP standalone export problem with Groovy scripts

  - by geejay

  I am trying to export a standalone RCP app using Eclipse 3.5.2. The app has a main pure Java plug-in, and a Java / Groovy plug-in that is used by the main plug-in. When I export the main RCP plug-in using the "Export Wizard", I get compiler errors saying that the Groovy classes cannot be found, e.g ERROR in C:\mysrc\src\ch\calcs\providers\CalcProvider.java (at line 8) import ch.calcs.ArgSet; This plug-in works fine when run from within Eclipse. Any ideas?

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• Deduce non-type template parameter

  - by pezcode

  Is it possible to deduce a non-type template parameter from a template function parameter? Consider this simple template: template <int N> constexpr int factorial() { return N * factorial<N - 1>(); } template <> constexpr int factorial<0>() { return 1; } template <> constexpr int factorial<1>() { return 1; } I would like to be able to change factorial so that I can alternatively call it like this: factorial(5); and let the compiler figure out the value of N at compile time. Is this possible? Maybe with some fancy C++11 addition?

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• Best way to get a random number from 1 to 50 which ISN'T x

  - by Cocorico

  Hi guys! So this is probably programming 101 stuff, but I have a problem: I have 2 numbers which are between 0 and 49. Let's call them x and y. Now I want to get a couple of other numbers which are not x or y, but are also between 0 and 49 (I am using Objective C but this is more of a general theory question I think?). Method I thought of is: int a; int b; int c; do { a = arc4random() % 49; } while ((a == x) || (a == y)); do { b = arc4random() % 49; } while ((b == x) || (b == y) || (b == a)); do { c = arc4random() % 49; } while ((c == x) || (c == y) || (c == a) || (c == b)); But it seem kind of bad to me, I don't know, I am just trying to learn to be a better programmer, what would be the most elegant sweet way to do this for best practices? Thanks!

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• Looking for a C# code parser

  - by Blindy

  I'm looking for a set of classes (preferably in the .net framework) that will parse C# code and return a list of functions with parameters, classes with their methods, properties etc. Ideally it would provide all that's needed to build my own intellisense. I have a feeling something like this should be in the .net framework, given all the reflection stuff they offer, but if not then an open source alternative is good enough. What I'm trying to build is basically something like Snippet Compiler, but with a twist. I'm trying to figure out how to get the code dom first. I tried googling for this but I'm not sure what the correct term for this is so I came up empty.

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• Compile-time trigonometry in C

  - by lhahne

  I currently have code that looks like while (very_long_loop) { ... y1 = getSomeValue(); ... x1 = y1*cos(PI/2); x2 = y2*cos(SOME_CONSTANT); ... outputValues(x1, x2, ...); } the obvious optimization would be to compute the cosines ahead-of-time. I could do this by filling an array with the values but I was wondering would it be possible to make the compiler compute these at compile-time?

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• Jquery number of clicks record

  - by Maxime

  Hi, I am working on this page where I'm using a Jquery Mp3 Player (Jplayer) with its playlist. What I want to do is very simple in theory: I want to record the number of clicks for every playlist element. When someone enters the page, his number of clicks are at 0 for every element. The visitor can click a few times on element #1, then go to element #2 (which will be at 0), then come back to element #1 and the number of clicks must be saved. We don't need to save it for next visits. Jplayer has this function that loads each time a new playlist element is being loaded: function playListChange( index ) In which every element has its own ID dynamically updated: myPlayList[index].song_id Here's my code: function playListChange( index ) { var id = myPlayList[index].song_id; if(!o) { var o = {}; } if(!o[id]) { o[id] = 0; } alert(o[id]); … $("#mydiv").click { o[id] = o[id]+1; } … But o[id] is reset every time and the alert always show 0. Why? Thanks for any reply.

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• Option Value Changed - ODBC Error 2169

  - by fredrick-ughimi

  Hello Edgar, Thank you for your response. I am using Powerbasic (www.powerbasic.com) as my compiler and SQLTools as a third party tool to access ADS through ODBC. I must stat that this error also appers when I take other actions like Update, Delete, Find, etc. But I don't get this error when I am using MS Access. Here is my save routine: [Code] Local sUsername As String Local sPassword As String Local sStatus As String Local sSQLStatement1 As String sUsername = VD_GetText (nCbHndl, %ID_FRMUPDATEUSERS_TXTUSERNAME) If Trim$(sUsername) = "" Then MsgBox "Please, enter Username", %MB_ICONINFORMATION Or %MB_TASKMODAL, VD_App.Title Control Set Focus nCbHndl, %ID_FRMUPDATEUSERS_TXTUSERNAME Exit Function End If sPassword = VD_GetText (nCbHndl, %ID_FRMUPDATEUSERS_TXTPASSWORD) If Trim$(sPassword) = "" Then MsgBox "Please, enter Password", %MB_ICONINFORMATION Or %MB_TASKMODAL, VD_App.Title Control Set Focus nCbHndl, %ID_FRMUPDATEUSERS_TXTPASSWORD Exit Function End If sStatus = VD_GetText (nCbHndl, %ID_FRMUPDATEUSERS_CBOSTATUS) sSQLStatement1 = "INSERT INTO [tblUsers] (Username, Password, Status) " + _ "VALUES ('" + sUsername + "','" + sPassword + "','" + sStatus +"')" 'Submit the SQL Statement to the database SQL_Stmt %SQL_STMT_IMMEDIATE, sSQLStatement1 'Check for errors If SQL_ErrorPending Then SQL_MsgBox SQL_ErrorQuickAll, %MSGBOX_OK End If [/code] Best regards,

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• xml to xsd to c# class - C# 3.0, .net 3.5

  - by uno

  Following this articlelink text one of the comments from 'zanoni' said he did it this way Using .NET 3.5: [XmlRoot] public class EmailConfiguration { [XmlElement] public string DataBoxID { get; set; } [XmlElement] public DefaultSendToAddressCollectionClass DefaultSendToAddressCollection { get; set; } } public class DefaultSendToAddressCollectionClass { [XmlElement] public string[] EmailAddress { get; set; } } How would I get my class to be as what he described? I ran the xsd tool and it is in the fashion as what shane posted in the above link [System.CodeDom.Compiler.GeneratedCodeAttribute("xsd", "2.0.50727.3038")] [System.SerializableAttribute()] [System.Diagnostics.DebuggerStepThroughAttribute()] [System.ComponentModel.DesignerCategoryAttribute("code")] [System.Xml.Serialization.XmlTypeAttribute(AnonymousType=true)] [System.Xml.Serialization.XmlRootAttribute(Namespace="", IsNullable=false)] public partial class EmailConfiguration : object, System.ComponentModel.INotifyPropertyChanged { private string dataBoxIDField; private EmailConfigurationDefaultSendToAddressCollection[] defaultSendToAddressCollectionField; /// <remarks/> [System.Xml.Serialization.XmlElementAttribute(Form=System.Xml.Schema.XmlSchemaForm.Unqualified)] public string DataBoxID { get { return this.dataBoxIDField; } set { this.dataBoxIDField = value; this.RaisePropertyChanged("DataBoxID"); } }

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• Does C# compile code inside an if(false) block?

  - by aximili

  I am just wondering if these code blocks gets compiled into .dll I don't think this one gets compiled at all #if SOMETHING_UNDEFINED // some code - this is ignored by the compiler #endif Now what about these? 1. if(false) { // some code - is this compiled? } 2. const bool F = false; if(F) { // some code - is this compiled? } 3. bool F = false; if(F) { // some code - is this compiled? }

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• Checking lazy loaded properties have been instantiated

  - by PaulG

  In a class which has a lazy loaded property, such as: private Collection<int> someInts; public Collection<int> SomeInts { get { if (this.someInts == null) this.someInts = new Collection<int>(); return this.someInts; } } Is it worth also having a property such as: public bool SomeIntsExist { get { return (this.someInts != null && this.someInts.Count > 0); } } And then using that property.. eg: if (thatClass.SomeIntsExist) { // do something with thatClass.SomeInts collection } or is this premature optimisation. Its certainly easier to roll with something like below, but it will instantiate the collection needlessly: if (thatClass.SomeInts.Count > 0) { // do something with thatClass.SomeInts collection } Is the compiler smart enough to figure things like this out? Is there a better way?

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• C++ MTL Library dimension.h bug?

  - by avanwieringen

  I've installed MTL on my Fedora Core 12 x64 system, but when building an application I get the following error: In file included from /usr/local/include/mtl/matrix.h:41, from /usr/local/include/mtl/mtl.h:40, from ltiSystem.hxx:4, from strTools.hxx:4, from ff.cxx:3: /usr/local/include/mtl/envelope2D.h:72: error: declaration of ‘typedef struct mtl::twod_tag mtl::envelope2D<T>::dimension’ /usr/local/include/mtl/dimension.h:19: error: changes meaning of ‘dimension’ from ‘class mtl::dimension<typename mtl::dense1D<T, 0>::size_type, 0, 0>’ make[1]: *** [ff.o] Error 1 Which would imply an error in MTL. I have changed to different MTL versions and the problem persists, but on Google there is no proper answer. I use the g++ compiler. Does anyone have a clye?

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• application trying to connect to mirrored sql db

  - by hp

  Hello, We have 4 web servers that host our asp.net (3.5) application. Randomly, we get error messages like : 1) "Login failed for user 'userid'" 2) "A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)" we are running sql2005 and have a principle and a mirror db (sync). When these exceptions are thrown, I look at the SQL error logs on the mirrored db and noticed the failed login messages in there. The principle db is running fine and the other web apps are working great. this will happen for maybe 10 min, then the app pool recycles and it starts hitting the principle db again. Is there a configuration I have incorrect? my theory is that our principle db is forwarding the request to the mirror, but that should never happen. any help??

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• How to free memory in try-catch blocks?

  - by Kra

  Hi, I have a simple question hopefully - how does one free memory which was allocated in the try block when the exception occurs? Consider the following code: try { char *heap = new char [50]; //let exception occur here delete[] heap; } catch (...) { cout << "Error, leaving function now"; //delete[] heap; doesn't work of course, heap is unknown to compiler return 1; } How can I free memory after the heap was allocated and exception occurred before calling delete[] heap? Is there a rule not to allocate memory on heap in these try .. catch blocks? Thanks

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• Create Generic Class Instance from Static Method in a Derived Class

  - by user343547

  I have a class in C# with a template and static method similar to class BClass<T> { public static BClass<T> Create() { return new BClass<T>(); } } From this I derive a class and specify a template parameter to the base class class DClass : BClass<int> { } A problem occurs when I try to use the static method to create an instance of D class Program { static void Main(string[] args) { DClass d = DClass.Create(); } } Gives a compiler error "Cannot implicitly convert type 'Test.BClass<int ' to 'Test.DClass'." Adding the below cast leads to a runtime casting exception. DClass d = (DClass)DClass.Create(); Is there any succint way to allow the static method to create instances of the derived class? Ideally I would like the equivalent of a c++ typedef and I don't want the below syntax (which does work). BClass<int> d = DClass.Create();

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• Can i have a negative value as constant expression in Scala?

  - by Klinke

  I have an Java-Annotation that return a double value: @Retention(RetentionPolicy.RUNTIME) @Target(ElementType.FIELD) public @interface DoubleValue { double value(); } When i try to attach the annotation to a field in a scala class and the value is negativ like here: class Test { @DoubleValue(-0.05) var a = _ } i get an compiler error with the message: "annotation argument needs to be a constant; found: 0.05.unary_-". I understood that i need a numerical literal and i looked into the Scala Language Specification and it seems, that the - sign is only used for the exponent but not for the mantissa. Does someone has an idea how i can have a negative value as runtime information using annotations? Thanks, Klinke

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• saving a records containing a member of type string to a file (Delphi, Windows)

  - by wonderer

  I have a record that looks similar to: type TNote = record Title : string; Note : string; Index : integer; end; Simple. The reason I chose to set the variables as string (as opposed to an array of chars) is that I have no idea how long those strings are going to be. They can be 1 char long, 200 or 2000. Of course when I try to save the record to a type file (file of...) the compiler complains that I have to give a size to string. Is there a way to overcome this? or a way to save those records to an untyped file and still maintain a sort of searchable way? Please do not point me to possible solutions, if you know the solution please post code. Thank you

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• DisplayName attribute from Resources?

  - by Palantir

  Hello! I have a localized application, and I am wondering if it is possible to have the DisplayName for a certain model property set from a Resource. I'd like to do something like this: public class MyModel { [Required] [DisplayName(Resources.Resources.labelForName)] public string name{ get; set; } } But I can't to it, as the compiler says: "An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type" :( Are there any workarounds? I am outputting labels manually, but I need these for the validator output!

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• Should I bundle C libraries with my Python application?

  - by oceanhug

  If I have a Python package that depends on some C libraries (like say the Gnu Scientific Library (GSL) for numerical computations), is it a good idea to bundle the library with my code? I'd like to make my package as easy to install as possible for users and I don't want them to have to download C libraries by hand and supply include-paths. Also I could always ensure that the version of the library that I ship is compatible with my code. However, is it possible that there are clashes if the user has the library installed already, or ar there any other reasons why I shouldn't do this? I know that I can make it easier for users by just providing a binary distribution, but I'd like to avoid having to maintain binary distributions for all possible OSs. So, I'd like to stick to a source distribution, but for the user (who proudly owns a C compiler) installation should be as easy as python setup.py install.

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