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• GDI+ is giving me errors

  - by user146780

  I want to use GDI + just to load a png. I included the headers and lib file then I do: Bitmap b; b.fromfile(filename); I get this from the compiler though. Error 1 error C2146: syntax error : missing ';' before identifier 'b' c:\users\josh\documents\visual studio 2008\projects\vectorizer project\vectorizer project\vectorizer project.cpp 23 Error 2 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\users\josh\documents\visual studio 2008\projects\vectorizer project\vectorizer project\vectorizer project.cpp 23 Error 3 error C4430: missing type specifier - int assumed. Note: C++ does not support default-int c:\users\josh\documents\visual studio 2008\projects\vectorizer project\vectorizer project\vectorizer project.cpp 23 Error 4 error C2440: '=' : cannot convert from 'const char [3]' to 'WCHAR *' c:\users\josh\documents\visual studio 2008\projects\vectorizer project\vectorizer project\vectorizer project.cpp 172 Error 5 error C2228: left of '.FromFile' must have class/struct/union c:\users\josh\documents\visual studio 2008\projects\vectorizer project\vectorizer project\vectorizer project.cpp 179 What is the correct way to do this? Thanks

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• Why does the the Java VM not recover after "Too many open files" errors?

  - by Michael

  In certain well-understood circumstances, our application will open too many sockets (database connections) and reach the maximum open files that the OS allows. We understand this; we are fixing the issue and also bumping up the limit. What we can't explain is why parts of our application don't recover even after the number of connections abates and we're well within the limit. In this case, it's an application running under Tomcat. When this happens, we first start seeing "Too many open files" errors: SEVERE: Socket accept failed java.net.SocketException: Too many open files at java.net.PlainSocketImpl.socketAccept(Native Method) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:390) at java.net.ServerSocket.implAccept(ServerSocket.java:453) at java.net.ServerSocket.accept(ServerSocket.java:421) at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:61) at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:310) at java.lang.Thread.run(Thread.java:619) Eventually, we start seeing NoClassDefFoundErrors inside an application thread that's trying to open HTTP connections: java.lang.NoClassDefFoundError: org/apache/commons/httpclient/protocol/ControllerThreadSocketFactory at org.apache.commons.httpclient.protocol.DefaultProtocolSocketFactory.createSocket(DefaultProtocolSocketFactory.java:128) at org.apache.commons.httpclient.HttpConnection.open(HttpConnection.java:707) at org.apache.commons.httpclient.MultiThreadedHttpConnectionManager$HttpConnectionAdapter.open(MultiThreadedHttpConnectionManager.java:1349) [...] Caused by: java.lang.ClassNotFoundException: org.apache.commons.httpclient.protocol.ControllerThreadSocketFactory at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1387) at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1233) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:320) ... 8 more When the errant connections go away, the server starts accepting connections again, and everything seems ok, but we're left with the latter error constantly being spewed to stderr. Although the application typically logs unloaded classes to stdout, I don't see any such logs just before, during or after the "Too many open files" errors. My initial theory was that the Hotspot JVM would unload seemingly unused classes when it encounters "Too many open files," but if so, it doesn't log the fact. I'd also expect it to recover if that were the case. Platform details: Java(TM) SE Runtime Environment (build 1.6.0_14-b08) Java HotSpot(TM) 64-Bit Server VM (build 14.0-b16, mixed mode) Apache Tomcat Version 6.0.18

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• Integrate Cppcheck with Emacs

  - by N.N.

  Is it possible to integrate Cppcheck with Emacs in a more sophisticated way than simply calling the shell command on the current buffer? I would like Emacs to be able to parse Cppcheck's messages and treat them as messages from a compiler (similar to how compile works), such as using C-x ` to visit the targets of Cppcheck's messages. Here is some example output Cppcheck: $ cppcheck --enable=all test.cpp Checking test.cpp... [test.cpp:4]: (error) Possible null pointer dereference: p - otherwise it is redundant to check if p is null at line 5 [test.cpp:38]: (style) The scope of the variable 'i' can be reduced [test.cpp:38]: (style) Variable 'i' is assigned a value that is never used [test.cpp:23]: (error) Possible null pointer dereference: p [test.cpp:33]: (error) Possible null pointer dereference: p Checking usage of global functions.. [test.cpp:36]: (style) The function 'f' is never used [test.cpp:1]: (style) The function 'f1' is never used [test.cpp:9]: (style) The function 'f2' is never used [test.cpp:26]: (style) The function 'f3' is never used

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• Compile-time lookup array creation for ANSI-C?

  - by multiproximus

  A previous programmer preferred to generate large lookup tables (arrays of constants) to save runtime CPU cycles rather than calculating values on the fly. He did this by creating custom Visual C++ projects that were unique for each individual lookup table... which generate array files that are then #included into a completely separate ANSI-C micro-controller (Renesas) project. This approach is fine for his original calculation assumptions, but has become tedious when the input parameters need to be modified, requiring me to recompile all of the Visual C++ projects and re-import those files into the ANSI-C project. What I would like to do is port the Visual C++ source directly into the ANSI-C microcontroller project and let the compiler create the array tables. So, my question is: Can ANSI-C compilers compute and generate lookup arrays during compile time? And if so, how should I go about it? Thanks in advance for your help!

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• Conflicting PACKAGE_NAME and other macros when using autotools.

  - by baol

  When using autotools (with a config.h file) for both a library and a software built on that library the compiler complains about a redefinition of some macros (PACKAGE_NAME, PACKAGE_TARNAME and so on). How can I prevent this? The config.h file is needed in the library to propagate it's setting to the software that use it. Right now I have a wrapper script library_config.h that includes the original config.h and provides defaults when the user is not using autotools, but even undefining the macros in that package I get the redefinition warning from gcc. #ifndef LIB_CONFIG_H #define LIB_CONFIG_H #ifdef HAVE_CONFIG_H # include "config.h" # undef PACKAGE # undef PACKAGE_BUGREPORT # undef PACKAGE_NAME # undef PACKAGE_STRING # undef PACKAGE_TARNAME # undef PACKAGE_VERSION # undef VERSION #else # if defined (WIN32) # define HAVE_UNORDERED_MAP 1 # define TR1_MIXED_NAMESPACE 1 # elif defined (__GXX_EXPERIMENTAL_CXX0X__) # define HAVE_UNORDERED_MAP 1 # else # define HAVE_TR1_UNORDERED_MAP 1 # endif #endif #endif I believe the best option would be to have a library without that macros: How can I avoid the definition of PACKAGE, PACKAGE_NAME and so on in the library when using autotools?

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• Noob-Ready Cython Tutorials

  - by spearfire

  I know a bunch of scripting languages, (python, ruby, lua, php) but I don't know any compiled languages like C/C++ , I wanted to try and speed up some python code using cython, which is essentially a python - C compiler, aimed at creating C extensions for python. Basically you code in a stricter version of python which compiles into C - native code. here's the problem, I don't know C, yet the cython documentation is aimed at people who obviously already know C (nothing is explained, only presented), and is of no help to me, I need to know if there are any good cython tutorials aimed at python programmers, or if I'm gonna have to learn C before I learn Cython. bear in mind I'm a competent python programmer, i would much rather learn cython from the perspective of the language I'm already good at, rather than learn a whole new language in order to learn cython. 1) PLEASE don't recommend psyco edit: ANY information that will help understand the oficial cython docs is useful information

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• Cross compiling unit tests with CppUnit or similar

  - by Mark

  Has anyone used a package like CppUnit to cross-compile C++ unit tests to run on an embedded platform? I'm using G++ on a Linux box to compile executables that must be run on a LynxOS board. I can't seem to get any of the common unit test packages to configure and build something that will create unit tests. I see a lot of unit test packages, CppUnit, UnitTest++, GTest, CppUTest, etc., but very little about using these packages in a cross-compiler scenario. The ones with a "configure" script imply that this is possible, but I can't seem to get them to configure and build.

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• Cython - properly declaring C funs

  - by deepblue

  I'm having trouble with running a bare example. I'm using this to declare a function in Cython coming from cinterf.h header: cdef extern from 'cinterf.h': int xsb_init_string(char* p_xsb_path) The declaration in the C header file is: DllExport extern int call_conv xsb_init_string(char *); both DllExport and call_conv are macros defined elsewhere, and resolve to GCC compiler directives. do I have to use those as well inside cdef to fully match the declaration? When I call xsb_init_string() as: xsb_init_string('some string') The python interpreter gives me: 'ImportError: ./py_ext.so: undefined symbol: xsb_init_string' Am I declaring the xsb_init_string() signature properly, inside cdef?

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• Recompile a x86 code with LLVM to some faster one x86

  - by osgx

  Hello Is it possible to run LLVM compiler with input of x86 32bit code? There is a huge algorithm which I have no source code and I want to make it run faster on the same hardware. Can I translate it from x86 back to x86 with optimizations. This Code runs a long time, so I want to do static recompilation of it. Also, I can do a runtime profile of it and give to LLVM hints, which branches are more probable. The original Code is written for x86, and uses no SSE/MMX/SSE2. After recompilation It has a chances to use x86_64 and/or SSE3. Also, The code will be regenerated in more optimal way to hardware decoder. Thanks.

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• Simple way to return anonymous types (to make MVC using LINQ possible)

  - by BlueRaja The Green Unicorn

  I'd like to implement MVC while using LINQ (specifically, LINQ-to-entities). The way I would do this is have the Controller generate (or call something which generates) the result-set using LINQ, then return that to the View to display the data. The problem is, if I do: return (from o in myTable select o); All the columns are read from the database, even the ones (potentially dozens) I don't want. And - more importantly - I can't do something like this: return (from o in myTable select new { o.column }); because there is no way to make anonymous types type-safe! I know for sure there is no nice, clean way of doing this in 3.5 (this is not clean...), but what about 4.0? Is there anything planned, or even proposed? Without something like duck-typing-for-LINQ, or type-safe anonymous return values (it seems to me the compiler should certainly be capable of that), it appears to be nearly impossible to cleanly separate the Controller from the View.

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• Computer science textbooks

  - by Barrett Conrad

  I would like to try the book question a little bit differently. My goal is to know what the community thinks are the quintessential computer science textbooks. <beginsadstory>I lost all of my computer science and math books from college in Hurricane Katrina in 2005. I greatly miss having my familiar tomes to refer to when topics and problems come up, so I am looking to rebuild my library.<endsadstory> What are your recommendations for the best examples of academic caliber books for the field of computer science and its associated mathematics? I am looking for books on subjects like computational theory, programming languages, compilers, operating systems, algorithms and so on. Don't limit your suggestions to your textbooks only. If there is a book you have read that covers computer science or a related math in a formal way, but is not strictly a textbook, I would be love to hear about them as well. Finally, for the sake of creating a good reference for all of us, may I suggest posting one book per answer so they can be rated individually.

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• What's all this fuss about?

  - by atch

  Hi guys, At the beginning I want to state that it is not my intention to upset anyone who uses/like language other than C++. I'm saying that due to the fact that on one forum everytime when I've tried to ask questions of similiar nature I was almost always accused of trying to create a raw. Ok that's having done this is my question: I don't understand why java/c# creators thought/think that having something like vm and having source code compiled to bytecode instead of native code is in a long run any advantage. And why having function compiled for a first time when they are invoked is any advantege? And what's the story about write once run everywhere? When I think about the business of having something written once and it can run everywhere - well in theory this is all well. But I know for a fact that in practice it doesn't look that well at all. It is rather like write once test everywhere. And why would I preffer something to be compiled on runtime instead of compiletime. If I would have to wait even one hour longer for program to be installed once and for all and all the compilation would be done and nothing would be compiled after that I would preffer that. And I don't really know how it works in the real world (I'm a student never worked in IT business) but for example if I have working program written in C++ for Windows and I have wish to move it to another platform wouldn't I have to take my source code and compile it on desired machine? So in other words isn't that rather problem of having compiler which will compile source code on different machines (as far as I'm concerned there is just one C++ and source code will look identical in every machine). And last but not least if you think about it how many programs they are which are really word porting? I personnally can think of 3 maybe four.

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• How to create generic class which takes 3 types.

  - by scope-creep

  I'm trying to make a generic class that takes 3 types, either a simple string, IList or a IList. public class OntologyStore { } public sealed class jim<T> where T:new() { IList<string> X = null; IList<OntologyStore> X1 = null; public bob() { if (typeof(T) == typeof(String)) { X = new List<string>(); } if (typeof(T) == typeof(OntologyStore)) { X1 = new List<OntologyStore>(); } } } I can easily create, which you would expect to work, jim<OntologyStore> x1=new jim<jim<OntologyStore>() as you would expect, but when I put in jim<string> x2=new jim<string>() the compiler reports the string is non abtract type, which you would expect. Is it possible to create a generic class, which can instantiate as a class which holds string, or a IList or an IList?

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• MVS 2008 and C99

  - by yCalleecharan

  Hi, I read with interest the post "How universally is C99 supported ?". One of the comments therein points that Microsoft doesn't support C99. But the comment symbol // works with MVS 2008 and this symbol is in C99. I have two questions: To what extent MVS 2008 support C99? Is it ok in the same code to mix C89 and C99 syntax together? So if I write my code in C89 and then place a comment //. This means that I have mixed-coding. So what does the compiler do in such a case? Check my code first with c89 and then with C99 to accept that I use // for commenting? Thanks a lot...

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• C# - Silverlight - CustomAttribute with Enum

  - by cmaduro

  I have the following class: [MetadataAttribute] [AttributeUsage(AttributeTargets.Property, AllowMultiple = false)] public class ModuleActivationButtonAttribute : ExportAttribute { public Enum TargetRegion { get; set; } public ModuleActivationButtonAttribute(Enum targetRegion) : base(typeof(IModuleActivationButton)) { TargetRegion = targetRegion; } } The class compiles fine, but when I decorate my property with it: [ModuleActivationButton(Regions.Tabs)] public IModuleActivationButton ModuleActivationButton { get { return new ModuleActivationButton() as IModuleActivationButton; } set { ModuleActivationButton = value; } } public enum Regions { Content, Tabs } The compiler spits out: Error 1 An attribute argument must be a constant expression, typeof expression or array creation expression of an attribute parameter type C:\...\Manpower4U.Modules.Home\HomeModule.cs 28 33 Manpower4U.Modules.Home

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• ::LookupAccountSid API Extremely Slow When Targeting x64 Platform (Windows 7)

  - by Chris

  During our application startup, we are making a call to ::LookupAccountSid(). When I build targeting the x86 architecture, this call is nearly instantaneous. However, when I target x64 (debug or release), the call generally takes over 40s to complete. Since this is occurring during application startup, the result is fairly unpleasant as it will appear to the user that the application is not launching. I am running Windows 7 Professional 64-bit on a Dell Studio XPS 16 (Intel Core i7 Q 720). Our application is a native Windows application written in C++. My compiler options (CCOPTS) and linker options (LINKOPTS) are as follows: CCOPTS = "/nologo /Gz /W3 /EHs /c /DWIN32 /D_MBCS /Ob1 /vmg /vmv /Zi /MD /DNDEBUG /DDV_BUILD_DLL /DIV_BUILD_DLL /DDVASSERT_EXCEPTION /Zc:wchar_t-" LINKOPTS = "/manifest:no /nologo /machine:X64 kernel32.lib user32.lib gdi32.lib winspool.lib comdlg32.lib advapi32.lib shell32.lib ole32.lib oleaut32.lib uuid.lib odbc32.lib odbccp32.lib /DEBUG /subsystem:windows /DLL" Any help would be greatly appreciated :D

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• Visual Studio ignore try catch - debug only

  - by Praesagus

  I think error handling is a good idea. :) When debugging it can get in the way - especially with nice user friendly messages. In VB6 I could just check a box for the compiler to ignore my error handling. I found the dialog that allows me to do something similar in VS, but it's about 10,000 check boxes instead of one - which is too many to change every time I want a production compilation. Is there a way to set VS up so when I am in debugging mode I get one set of conditions and when I am in production I get another? ...or is there just another method to handling errors and debugging more efficiently? Thanks

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• Choosing random numbers efficiently

  - by Frederik Wordenskjold

  I have a method, which uses random samples to approximate a calculation. This method is called millions of times, so its very important that the process of choosing the random numbers is efficient. I'm not sure how fast javas Random().nextInt really are, but my program does not seem to benefit as much as I would like it too. When choosing the random numbers, I do the following (in semi pseudo-code): // Repeat this 300000 times Set set = new Set(); while(set.length != 5) set.add(randomNumber(MIN,MAX)); Now, this obviously has a bad worst-case running time, as the random-function in theory can add duplicated numbers for an eternity, thus staying in the while-loop forever. However, the numbers are chosen from {0..45}, so a duplicated value is for the most part unlikely. When I use the above method, its only 40% faster than my other method, which does not approximate, but yields the correct result. This is ran ~ 1 million times, so I was expecting this new method to be at least 50% faster. Do you have any suggestions for a faster method? Or maybe you know of a more efficient way of generation a set of random numbers.

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• MVC using LINQ? - Can't return anonymous types

  - by BlueRaja

  I'd like to implement MVC while using LINQ (specifically, LINQ-to-entities). The way I would do this is have the Controller generate (or call something which generates) the result-set using LINQ, then return that to the View to display the data. The problem is, if I do: return (from o in myTable select o); All the columns are read from the database, even the ones (potentially dozens) I don't want. And - more importantly - I can't do something like this: return (from o in myTable select new { o.column }); because there is no way to make anonymous types type-safe! I know for sure there is no nice, clean way of doing this in 3.5 (this is not clean...), but what about 4.0? Is there anything planned, or even proposed? Without something like duck-typing-for-LINQ, or type-safe anonymous return values (it seems to me the compiler should certainly be capable of that), it appears to be nearly impossible to cleanly separate the Controller from the View.

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• Is it worth learning Perl 6?

  - by Andres

  I have the opportunity to take a two day class on Perl 6 with the Rakudo Compiler. I don't want to start a religious war, but is it worth my time? Is there any reason to believe that Perl 6 will be practical in the real world within the next two years? Does anyone currently use it effectively? Update I took the class and learned a lot. However, after day 1, my mind was a bit overwhelmed. There are tons of cool ideas in perl 6, and it will be neat to see what filters up to other languages. Overall the experience was a positive use of my time, though I wasn't able to absorb as much on the second day. If it were a three day class it would have been unproductive just because there is a limit to how much you can process in a short amount of time.

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• XML documentation to context sensitive help

  - by Yonas

  These days a number of commercial and open source tools have been developed for this purpose. However(unfortunately), non of them meet my requirement for specific problem I am dealing with. Currently, I am working on a project that exposes a different classes and functions to user as scripting interface. the user can use the objects from custom scripting interface and call methods to solve some specific problem. The problem I am facing is users of my classes need some sort of documentation in order to write their script efficiently. To address this problem am planing to use the compiler generated XML file to provide context sensitive help, which allows users to mouse over on any of the controls and corresponding methods from the GUI and read the reference documentation of the class/method. Now ... here are my questions: Can I get the sample source code? Can any one give me someone point me to some sort of best approach to address the problem?

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• Java "constant string too long" compile error. Only happens using Ant, not when using Eclipse

  - by Allan

  I have a few really long strings in one class for initializing user information. When I compile in Eclipse, I don't get any errors or warnings, and the resulting .jar runs fine. Recently, I decided to create an ant build file to use. Whenever I compile the same class with ant, I get the "constant string too long" compile error. I've tried a number of ways to set the java compiler executable in ant to make sure that I'm using the exact same version as in Eclipse. I'd rather figure out how to get the same successful compile I get in Eclipse in Ant than try to rework the code to dynamically concatenate the strings.

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• What do I return if the return type of a method is Void? (Not void!)

  - by DR

  Due to the use of Generics in Java I ended up in having to implement a function having Void as return type: public Void doSomething() { //... } and the compiler demands that I return something. For now I'm just returning null, but I'm wondering if that is good coding practice... I've also tried Void.class, void, Void.TYPE, new Void(), no return at all, but all that doesn't work at all. (For more or less obvious reasons) (See this answer for details) So what am I supposed to return if the return type of a function is Void? What's the general use of the Void class? EDIT: Just to spare you the downvotes: I'm asking about V?oid, not v?oid. The class Void, not the reserved keyword void.

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• WCF- "The underlying connection was closed: The connection was closed unexpectedly"

  - by SumGuy

  Hi there. I'm recieving that wonderfuly ambiguous error message when using one of my webmethods on my WCF webservice. As that error message doesn't provide any explanation whatsoever allow me to post my theory. I believe it may have something to do with the return type I'm using I have a Types DLL which is refrenced in both the webservice and the client. In this DLL is the base class ExceptionMessages. There is a child of this class called DrawingExcepions. Here is some code: public class ExceptionMessages { public object[] ReturnValue { get; set; } } public class DrawingExceptions : ExceptionMessages { private List<DrawingException> des = new List<DrawingException>(); } public class DrawingException { public Exception ExceptionMsg { get; set; } public List<object> Errors { get; set; } } The using code: [OperationContract] ExceptionMessages createNewBom(Bom bom, DrawingFiles dfs); public ExceptionMessages createNewBOM(Bom bom, DrawingFiles dfs) { return insertAssembly(bom, dfs); } public DrawingExceptions insertAssembly(Bom bom, DrawingFiles dfs) { DrawingExceptions des = new DrawingExceptions(); foreach (DrawingFile d in dfs.drawingFiles) { DrawingException temp = insertNewDrawing(bom, d); if (temp != null) des.addDrawingException(temp); if (d.Child != null) des.addDrawingException(insertAssembly(bom, d.Child)); } return des; } Returns to: ExceptionMessages ems = client.createNewBom(bom, currentDFS); if (ems is DrawingExceptions) { } Basically the return type from the webmethod is ExceptionMessages however I would usually be sending the child class back instead. My only idea is that it's the child that's causing the error but as far as I've read, this should have no effect. Has anyone got any ideas what could be going wrong here? If any more info is required, just ask :) Thanks.

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• Are preprocessors obsolete in modern languages?

  - by Earlz

  Hello, I'm making a simple compiler for a simple pet language I'm creating and coming from a C background(though I'm writing it in Ruby) I wondered if a preprocessor is necessary. What do you think? Is a "dumb" preprocessor still necessary in modern languages? Would C#'s conditional compilation capabilities be considered a "preprocessor"? Does every modern language that doesn't include a preprocessor have the utilities necessary to properly replace it? (for instance, the C++ preprocessor is now mostly obsolete(though still depended upon) because of templates.)

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