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• Please help with C++ syntax for const accessor by reference.

  - by Hamish Grubijan

  Right not my implementation returns the thing by value. The member m_MyObj itself is not const - it's value changes depending on what the user selects with a Combo Box. I am no C++ guru, but I want to do this right. If I simply stick a & in front of GetChosenSourceSystem in both decl. and impl., I get one sort of compiler error. If I do one but not another - another error. If I do return &m_MyObj;. I will not list the errors here for now, unless there is a strong demand for it. I assume that an experienced C++ coder can tell what is going on here. I could omit constness or reference, but I want to make it tight and learn in the process as well. Thanks! // In header file MyObj GetChosenThingy() const; // In Implementation file. MyObj MyDlg::GetChosenThingy() const { return m_MyObj; }

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• Beginner C++ - Trouble using global constants in a header file

  - by Francisco P.

  Hello! Yet another Scrabble project question... This is a simple one. It seems I am having trouble getting my global constants recognized: My board.h: http://pastebin.com/R10HrYVT Errors returned: 1>C:\Users\Francisco\Documents\FEUP\1A2S\PROG\projecto3\projecto3\Board.h(34): error: variable "TOTAL_ROWS" is not a type name 1> vector< vector<Cell> > _matrix(TOTAL_ROWS , vector<Cell>(TOTAL_COLUMNS)); 1> 1>main.cpp 1>compilation aborted for .\Game.cpp (code 2) 1>Board.cpp 1>.\Board.h(34): error: variable "TOTAL_ROWS" is not a type name 1> vector< vector<Cell> > _matrix(TOTAL_ROWS , vector<Cell>(TOTAL_COLUMNS)); 1> ^ 1> Why does this happen? Why is the compiler expecting types? Thanks for your time!

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• Foreign key relationships in Entity Framework

  - by Anders Svensson

  I'm trying to add an object created from Entity Data Model classes. I have a table called Users, which has turned into a User EDM class. And I also have a table Pages, which has become a Page EDM class. These tables have a foreign key relationship, so that each page is associated with many users. Now I want to be able to add a page, but I can't get how to do it. I get a nullreference exception on Users below. I'm still rather confused by all this, so I'm sure it's a simple error, but I just can't see how to do it. Also, by the way, the compiler requires that I set PageID in the object initializer, even though this field is set to be an automatic id in the table. Am I doing it right just setting it to 0, expecting it to be updated automatically in the table when saved, or how should I do that? Any help appreciated! The method in question: private Page GetPage(User currentUser) { string url = _request.ServerVariables["url"].ToLower(); var userPages = from p in _context.PageSet where p.Users.UserID == currentUser.UserID select p; var existingPage = userPages.FirstOrDefault(e => e.Url == url); //Could be combined with above, but hard to read? if (existingPage != null) return existingPage; Page page = new Page() { Count = 0, Url = _request.ServerVariables["url"].ToLower(), PageID = 0, //Only initial value, changed later? }; _context.AddToPageSet(page); page.Users.UserID = currentUser.UserID; //Here's the problem... return page; }

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• How are two-dimensional arrays formatted in memory?

  - by Chris Cooper

  In C, I know I can dynamically allocate a two-dimensional array on the heap using the following code: int** someNumbers = malloc(arrayRows*sizeof(int*)); for (i = 0; i < arrayRows; i++) { someNumbers[i] = malloc(arrayColumns*sizeof(int)); } Clearly, this actually creates a one-dimensional array of pointers to a bunch of separate one-dimensional arrays of integers, and "The System" can figure you what I mean when I ask for: someNumbers[4][2]; But when I statically declare a 2D array, as in the following line...: int someNumbers[ARRAY_ROWS][ARRAY_COLUMNS]; ...does a similar structure get created on the stack, or is it of another form completely? (i.e. is it a 1D array of pointers? If not, what is it, and how do references to it get figured out?) Also, when I said, "The System," what is actually responsible for figuring that out? The kernel? Or does the C compiler sort it out while compiling?

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• final transient fields and serialization

  - by doublep

  Is it possible to have final transient fields that are set to any non-default value after serialization in Java? My usecase is a cache variable — that's why it is transient. I also have a habit of making Map fields that won't be changed (i.e. contents of the map is changed, but object itself remains the same) final. However, these attributes seem to be contradictory — while compiler allows such a combination, I cannot have the field set to anything but null after unserialization. I tried the following, without success: simple field initialization (shown in the example): this is what I normally do, but the initialization doesn't seem to happen after unserialization; initialization in constructor (I believe this is semantically the same as above though); assigning the field in readObject() — cannot be done since the field is final. In the example cache is public only for testing. import java.io.*; import java.util.*; public class test { public static void main (String[] args) throws Exception { X x = new X (); System.out.println (x + " " + x.cache); ByteArrayOutputStream buffer = new ByteArrayOutputStream (); new ObjectOutputStream (buffer).writeObject (x); x = (X) new ObjectInputStream (new ByteArrayInputStream (buffer.toByteArray ())).readObject (); System.out.println (x + " " + x.cache); } public static class X implements Serializable { public final transient Map <Object, Object> cache = new HashMap <Object, Object> (); } } Output: test$X@1a46e30 {} test$X@190d11 null

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• Run arbitrary subprocesses on Windows and still terminate cleanly?

  - by Weeble

  I have an application A that I would like to be able to invoke arbitrary other processes as specified by a user in a configuration file. Batch script B is one such process a user would like to be invoked by A. B sets up some environment variables, shows some messages and invokes a compiler C to do some work. Does Windows provide a standard way for arbitrary processes to be terminated cleanly? Suppose A is run in a console and receives a CTRL+C. Can it pass this on to B and C? Suppose A runs in a window and the user tries to close the window, can it cancel B and C? TerminateProcess is an option, but not a very good one. If A uses TerminateProcess on B, C keeps running. This could cause nasty problems if C is long-running, since we might start another instance of C to operate on the same files while the first instance of C is still secretly at work. In addition, TerminateProcess doesn't result in a clean exit. GenerateConsoleCtrlEvent sounds nice, and might work when everything's running in a console, but the documentation says that you can only send CTRL+C to your own console, and so wouldn't help if A were running in a window. Is there any equivalent to SIGINT on Windows? I would love to find an article like this one: http://www.cons.org/cracauer/sigint.html for Windows.

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• Extending the method pool of a concrete class which is derived by an interface

  - by CelGene

  Hello, I had created an interface to abstract a part of the source for a later extension. But what if I want to extend the derived classes with some special methods? So I have the interface here: class virtualFoo { public: virtual ~virtualFoo() { } virtual void create() = 0; virtual void initialize() = 0; }; and one derived class with an extra method: class concreteFoo : public virtualFoo { public: concreteFoo() { } ~concreteFoo() { } virtual void create() { } virtual void initialize() { } void ownMethod() { } }; So I try to create an Instance of concreteFoo and try to call ownMethod like this: void main() { virtualFoo* ptr = new concreteFoo(); concreteFoo* ptr2 = dynamic_cast(ptr); if(NULL != ptr2) ptr2->ownMethod(); } It works but is not really the elegant way. If I would try to use ptr-ownMethod(); directly the compiler complains that this method is not part of virtualFoo. Is there a chance to do this without using dynamic_cast? Thanks in advance!

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• Resources and techniques/methods for SCJP preparation ?

  - by BenoitParis

  I am passing the SCJP 6 exam in a month. I have the "SCJP Sun Certified Programmer for Java 6 Exam 310-065" book. It seems great for the exam. But I want your advice on this. Getting the closest possible to 100% would be great. I have found a site that answered some of the questions you ask yourself when you go trough the book. Here is it : http://www.janeg.ca/java2.html As you can see it was written for Java 2 :/ I have written another specific question here on StackOverflow about the usefulness of JVM specification and Java compiler code for the SCJP. Will Update the results here. Here it is. Please share the resources you used in preparing the exam. Please also specify any resources that you think might help. Any type of resource is welcome: books, code, specs, sites, wikies, papers, online tests, grandmas... Please also share on any method/technique that helped you prepare the exam. Please also comment on the return you got from the resource and the method (for the learning process and for points in the exam) I'll begin: Book : "SCJP Sun Certified Programmer for Java 6 Exam 310-065". Seems like the official book for the preparation. Technique : Writing code in a text editor and compiling it with javac to test a question. NO IDEs! It helps you get a a straight answer to a question you have. It helps you pay attention to every word in the code (and this is very important in the SCJP) EDIT: Added dimension: Are there good, up-to-date online tests?

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• Does it ever make sense to make a fundamental (non-pointer) parameter const?

  - by Scott Smith

  I recently had an exchange with another C++ developer about the following use of const: void Foo(const int bar); He felt that using const in this way was good practice. I argued that it does nothing for the caller of the function (since a copy of the argument was going to be passed, there is no additional guarantee of safety with regard to overwrite). In addition, doing this prevents the implementer of Foo from modifying their private copy of the argument. So, it both mandates and advertises an implementation detail. Not the end of the world, but certainly not something to be recommended as good practice. I'm curious as to what others think on this issue. Edit: OK, I didn't realize that const-ness of the arguments didn't factor into the signature of the function. So, it is possible to mark the arguments as const in the implementation (.cpp), and not in the header (.h) - and the compiler is fine with that. That being the case, I guess the policy should be the same for making local variables const. One could make the argument that having different looking signatures in the header and source file would confuse others (as it would have confused me). While I try to follow the Principle of Least Astonishment with whatever I write, I guess it's reasonable to expect developers to recognize this as legal and useful.

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• Some questions about special operators i've never seen in C++ code.

  - by toto

  I have downloaded the Phoenix SDK June 2008 (Tools for compilers) and when I'm reading the code of the Hello sample, I really feel lost. public ref class Hello { //-------------------------------------------------------------------------- // // Description: // // Class Variables. // // Remarks: // // A normal compiler would have more flexible means for holding // on to all this information, but in our case it's simplest (if // somewhat inelegant) if we just keep references to all the // structures we'll need to access as classstatic variables. // //-------------------------------------------------------------------------- static Phx::ModuleUnit ^ module; static Phx::Targets::Runtimes::Runtime ^ runtime; static Phx::Targets::Architectures::Architecture ^ architecture; static Phx::Lifetime ^ lifetime; static Phx::Types::Table ^ typeTable; static Phx::Symbols::Table ^ symbolTable; static Phx::Phases::PhaseConfiguration ^ phaseConfiguration; 2 Questions : What's that ref keyword? What is that sign ^ ? What is it doing protected: virtual void Execute ( Phx::Unit ^ unit ) override; }; override is a C++ keyword too? It's colored as such in my Visual Studio. I really want to play with this framework, but this advanced C++ is really an obstacle right now. Thank you.

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• Problem with Boost::Asio for C++

  - by Martin Lauridsen

  Hi there, For my bachelors thesis, I am implementing a distributed version of an algorithm for factoring large integers (finding the prime factorisation). This has applications in e.g. security of the RSA cryptosystem. My vision is, that clients (linux or windows) will download an application and compute some numbers (these are independant, thus suited for parallelization). The numbers (not found very often), will be sent to a master server, to collect these numbers. Once enough numbers have been collected by the master server, it will do the rest of the computation, which cannot be easily parallelized. Anyhow, to the technicalities. I was thinking to use Boost::Asio to do a socket client/server implementation, for the clients communication with the master server. Since I want to compile for both linux and windows, I thought windows would be as good a place to start as any. So I downloaded the Boost library and compiled it, as it said on the Boost Getting Started page: bootstrap .\bjam It all compiled just fine. Then I try to compile one of the tutorial examples, client.cpp, from Asio, found (here.. edit: cant post link because of restrictions). I am using the Visual C++ compiler from Microsoft Visual Studio 2008, like this: cl /EHsc /I D:\Downloads\boost_1_42_0 client.cpp But I get this error: /out:client.exe client.obj LINK : fatal error LNK1104: cannot open file 'libboost_system-vc90-mt-s-1_42.lib' Anyone have any idea what could be wrong, or how I could move forward? I have been trying pretty much all week, to get a simple client/server socket program for c++ working, but with no luck. Serious frustration kicking in. Thank you in advance.

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• C++ Constructor initialization list strangeness

  - by Andy

  I have always been a good boy when writing my classes, prefixing all member variables with m_: class Test { int m_int1; int m_int2; public: Test(int int1, int int2) : m_int1(int int1), m_int2(int int2) {} }; void main() { Test t(10, 20); // Just an example } However, recently I forgot to do that and ended up writing: class Test { int int1; int int2; public: // Very questionable, but of course I meant to assign ::int1 to this->int1! Test(int int1, int int2) : int1(int1), int2(int2) {} }; Believe it or not, the code compiled with no errors/warnings and the assignments took place correctly! It was only when doing the final check before checking in my code when I realised what I had done. My question is: why did my code compile? Is something like that allowed in the C++ standard, or is it simply a case of the compiler being clever? In case you were wondering, I was using Visual Studio 2008 Thank you.

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• ojspc always returns 0 on errors

  - by Matt McCormick

  In my Ant build.xml file, I am trying to compile JSPs using ojspc. The files are being compiled, however, the build process is still running to completion when the JSP compilation has errors. This is part of my build.xml: <java fork="true" jar="${env.ORACLE_HOME}\j2ee\home\ojspc.jar" resultproperty="result"> <jvmarg value="-Djava.compiler=NONE"/> <arg value="-extend"/> <arg value="com.orionserver.http.OrionHttpJspPage"/> <arg value="-batchMask"/> <arg value="*.jsp"/> <arg value="${target-directory}/build/target/ear/${module-dir-name}-jsp.war"/> </java> <echo level="info">Result Property: ${result}</echo> I have tried setting the property failonerror="true" but that does not change anything. I receive the following output: [java] Detected archive, now processing contents of ../build/target/ear/web-module-jsp.war... [java] Setting up temp area... [java] Expanding archive in temp area... [java] C:\DOCUME~1\MMCCOR~1\LOCALS~1\Temp\tmp12940\_web_2d_inf\_jsp\_password.java:60: cannot resolve symbol [java] symbol : variable reqvst [java] location: class _web_2d_inf._jsp._password [java] out.print(reqvst.getAttribute("test")); [java] ^ [java] 1 error [java] Creating D:\eclipse-workspace\jdw\build\..\build\target\ear\web-module-jsp.war ... [java] Removing temp area... [echo] Result Property: 0 ...(more commands) BUILD SUCCESSFUL In the password.jsp file, I intentionally introduced an error to test. How can I get the build to fail on an error? At the Ant Java page, I am confused by: By default the return code of a is ignored. Alternatively, you can set resultproperty to the name of a property and have it assigned to the result code (barring immutability, of course). When you set failonerror="true", the only possible value for resultproperty is 0. Any non-zero response is treated as an error and would mean the build exits.

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• Delphi: How to avoid EIntOverflow underflow when subtracting?

  - by Ian Boyd

  Microsoft already says, in the documentation for GetTickCount, that you could never compare tick counts to check if an interval has passed. e.g.: Incorrect (pseudo-code): DWORD endTime = GetTickCount + 10000; //10 s from now ... if (GetTickCount > endTime) break; The above code is bad because it is suceptable to rollover of the tick counter. For example, assume that the clock is near the end of it's range: endTime = 0xfffffe00 + 10000 = 0x00002510; //9,488 decimal Then you perform your check: if (GetTickCount > endTime) Which is satisfied immediatly, since GetTickCount is larger than endTime: if (0xfffffe01 > 0x00002510) The solution Instead you should always subtract the two time intervals: DWORD startTime = GetTickCount; ... if (GetTickCount - startTime) > 10000 //if it's been 10 seconds break; Looking at the same math: if (GetTickCount - startTime) > 10000 if (0xfffffe01 - 0xfffffe00) > 10000 if (1 > 10000) Which is all well and good in C/C++, where the compiler behaves a certain way. But what about Delphi? But when i perform the same math in Delphi, with overflow checking on ({Q+}, {$OVERFLOWCHECKS ON}), the subtraction of the two tick counts generates an EIntOverflow exception when the TickCount rolls over: if (0x00000100 - 0xffffff00) > 10000 0x00000100 - 0xffffff00 = 0x00000200 What is the intended solution for this problem? Edit: i've tried to temporarily turn off OVERFLOWCHECKS: {$OVERFLOWCHECKS OFF}] delta = GetTickCount - startTime; {$OVERFLOWCHECKS ON} But the subtraction still throws an EIntOverflow exception. Is there a better solution, involving casts and larger intermediate variable types?

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• Trying to make a plugin system in C++

  - by Pirate for Profit

  I'm making a task-based program that needs to have plugins. Tasks need to have properties which can be easily edited, I think this can be done with Qt's Meta-Object Compiler reflection capabilities (I could be wrong, but I should be able to stick this in a QtPropertyBrowser?) So here's the base: class Task : public QObject { Q_OBJECT public: explicit Task(QObject *parent = 0) : QObject(parent){} virtual void run() = 0; signals: void taskFinished(bool success = true); } Then a plugin might have this task: class PrinterTask : public Task { Q_OBJECT public: explicit PrinterTask(QObject *parent = 0) : Task(parent) {} void run() { Printer::getInstance()->Print(this->getData()); // fictional emit taskFinished(true); } inline const QString &getData() const; inline void setData(QString data); Q_PROPERTY(QString data READ getData WRITE setData) // for reflection } In a nutshell, here's what I want to do: // load plugin // find all the Tasks interface implementations in it // have user able to choose a Task and edit its specific Q_PROPERTY's // run the TASK It's important that one .dll has multiple tasks, because I want them to be associated by their module. For instance, "FileTasks.dll" could have tasks for deleting files, making files, etc. The only problem with Qt's plugin setup is I want to store X amount of Tasks in one .dll module. As far as I can tell, you can only load one interface per plugin (I could be wrong?). If so, the only possible way to do accomplish what I want is to create a FactoryInterface with string based keys which return the objects (as in Qt's Plug-And-Paint example), which is a terrible boilerplate that I would like to avoid. Anyone know a cleaner C++ plugin architecture than Qt's to do what I want? Also, am I safely assuming Qt's reflection capabilities will do what I want (i.e. able to edit an unknown dynamically loaded tasks' properties with the QtPropertyBrowser before dispatching)?

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• How do I access Dictionary items?

  - by salvationishere

  I am developing a C# VS2008 / SQL Server website app and am new to the Dictionary class. Can you please advise on best method of accomplishing this? Here is a code snippet: SqlConnection conn2 = new SqlConnection(connString); SqlCommand cmd = conn2.CreateCommand(); cmd.CommandText = "dbo.AppendDataCT"; cmd.CommandType = CommandType.StoredProcedure; cmd.Connection = conn2; SqlParameter p1, p2, p3; foreach (string s in dt.Rows[1].ItemArray) { DataRow dr = dt.Rows[1]; // second row p1 = cmd.Parameters.AddWithValue((string)dic[0], (string)dr[0]); p1.SqlDbType = SqlDbType.VarChar; p2 = cmd.Parameters.AddWithValue((string)dic[1], (string)dr[1]); p2.SqlDbType = SqlDbType.VarChar; p3 = cmd.Parameters.AddWithValue((string)dic[2], (string)dr[2]); p3.SqlDbType = SqlDbType.VarChar; } but this is giving me compiler error: The best overloaded method match for 'System.Collections.Generic.Dictionary<string,string>.this[string]' has some invalid arguments I just want to access each value from "dic" and load into these SQL parameters. How do I do this? Do I have to enter the key? The keys are named "col1", "col2", etc., so not the most user-friendly. Any other tips? Thanks!

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• Why do .NET developers offer 32-bit/64-bit versions of .NET assemblies?

  - by Tyler

  Evey now and then I see both x86 and x64 versions of a .NET assembly. Consider the following web part for SharePoint. Why wouldn't the developer just offer a single version and have let the JIT compiler sort out the rest? When I see these kinds offering is it just that the developer decided to create a native image using a tool like ngen in order to avoid a JIT? Someone please help me out here, I feel like I'm missing something of note. Updated From what I got below, both x86 and x64 builds are offered because one or more of the following reasons: The developer wanted to avoid JITing and created a native image of his code, targeting a given architecture using a tool like ngen.exe. The assembly contains platform specific COM calls and so it makes no point to build it as AnyCPU. In these cases builds that target different platforms may contain different code. The assembly may contain Win32 calls using pinvoke which won't get remapped by a JIT and so the build should target the platform it is bound to.

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• Putting all methods in class definition

  - by Amnon

  When I use the pimpl idiom, is it a good idea to put all the methods definitions inside the class definition? For example: // in A.h class A { class impl; boost::scoped_ptr<impl> pimpl; public: A(); int foo(); } // in A.cpp class A::impl { // method defined in class int foo() { return 42; } // as opposed to only declaring the method, and defining elsewhere: float bar(); }; A::A() : pimpl(new impl) { } int A::foo() { return pimpl->foo(); } As far as I know, the only problems with putting a method definition inside a class definition is that (1) the implementation is visible in files that include the class definition, and (2) the compiler may make the method inline. These are not problems in this case since the class is defined in a private file, and inlining has no effect since the methods are called in only one place. The advantage of putting the definition inside the class is that you don't have to repeat the method signature. So, is this OK? Are there any other issues to be aware of?

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• how to filter files from the root "classes" and "test-classes" folders in Eclipse?

  - by Kidburla

  I am using ClearCase in my application which generates a whole load of ".copyarea.db" files (one in every folder). These cause conflicts when publishing to Tomcat as Eclipse will bundle the "classes" and "test-classes" folders into one JAR (not sure why it does this - as there is no need to have test classes available on the application server). Any folders with the same names will have a separate .copyarea.db in the classes and test-classes branches. I managed to get around this problem in general by adding ".copyarea.db" to the Filtered resources on the Java->Compiler->Building->Output Folder preference page. This stops the file appearing in source output (package/class folders), the vast majority of cases. However there remains the problem of the root folder, i.e. "target/classes/.copyarea.db" and "target/test-classes/.copyarea.db". These files are not filtered as they are not part of the compile task. Just deleting the files manually doesn't help either, as Eclipse expects to find them and doesn't. How can I exclude these ".copyarea.db" files from the root "classes" and "test-classes" folders?

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• GWT - problems with constants in css

  - by hba

  Hi, I'm new to GWT; I'm building a small sample app. I have several CSS files. I'm able to successfully use the ClientBundle and CssResource to assign styles to the elements defined in my UiBinder script. Now I'd like to take it one step further and introduce CSS constants using @def css-rule. The @def works great when I define a constant and use it in the same CSS file. However I cannot use it in another CSS file. When I try to use the @eval rule to evaluate an existing constant the compiler throws an execption: "cannot make a static reference to the non-static method ". Here is an example of what I'm trying to do: ConstantStyle.css @def BACKGROUND red; ConstantStyle.java package abc; import ...; interface ConstantStyle extends cssResource { String BACKGROUND(); } MyStyle.css @eval BACKGROUND abc.ConstantStyle.BACKGROUND(); .myClass {background-color: BACKGROUND;} MyStyle.java package abc; import ...; interface ConstantStyle extends cssResource { String myClass; } MyResources.java package abc; import ...; interface MyResources extends ClientBundle { @Source("ConstantStyle.css") ConstantStyle constantStyle(); @Source("MyStyle.css") MyStyle myStyle(); } Thanks in advance!

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• Freestanding ARM C++ Code - empty .ctors section

  - by Matthew Iselin

  I'm writing C++ code to run in a freestanding environment (basically an ARM board). It's been going well except I've run into a stumbling block - global static constructors. To my understanding the .ctors section contains a list of addresses to each static constructor, and my code simply needs to iterate this list and make calls to each function as it goes. However, I've found that this section in my binary is in fact completely empty! Google pointed towards using ".init_array" instead of ".ctors" (an EABI thing), but that has not changed anything. Any ideas as to why my static constructors don't exist? Relevant linker script and objdump output follows: .ctors : { . = ALIGN(4096); start_ctors = .; *(.init_array); *(.ctors); end_ctors = .; } .dtors : { . = ALIGN(4096); start_dtors = .; *(.fini_array); *(.dtors); end_dtors = .; } -- 2 .ctors 00001000 8014c000 8014c000 00054000 2**2 CONTENTS, ALLOC, LOAD, DATA <snip> 8014d000 g O .ctors 00000004 start_ctors <snip> 8014d000 g O .ctors 00000004 end_ctors I'm using an arm-elf targeted GCC compiler (4.4.1).

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• Preprocessor "macro function" vs. function pointer - best practice?

  - by Dustin

  I recently started a small personal project (RGB value to BGR value conversion program) in C, and I realised that a function that converts from RGB to BGR can not only perform the conversion but also the inversion. Obviously that means I don't really need two functions rgb2bgr and bgr2rgb. However, does it matter whether I use a function pointer instead of a macro? For example: int rgb2bgr (const int rgb); /* * Should I do this because it allows the compiler to issue * appropriate error messages using the proper function name, * not to mention possible debugging benefits? */ int (*bgr2rgb) (const int bgr) = rgb2bgr; /* * Or should I do this since it is merely a convenience * and they're really the same function anyway? */ #define bgr2rgb(bgr) (rgb2bgr (bgr)) I'm not necessarily looking for a change in execution efficiency as it's more of a subjective question out of curiosity. I am well aware of the fact that type safety is neither lost nor gained using either method. Would the function pointer merely be a convenience or are there more practical benefits to be gained of which I am unaware?

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• On C++ global operator new: why it can be replaced

  - by Jimmy

  I wrote a small program in VS2005 to test whether C++ global operator new can be overloaded. It can. #include "stdafx.h" #include "iostream" #include "iomanip" #include "string" #include "new" using namespace std; class C { public: C() { cout<<"CTOR"<<endl; } }; void * operator new(size_t size) { cout<<"my overload of global plain old new"<<endl; // try to allocate size bytes void *p = malloc(size); return (p); } int main() { C* pc1 = new C; cin.get(); return 0; } In the above, my definition of operator new is called. If I remove that function from the code, then operator new in C:\Program Files (x86)\Microsoft Visual Studio 8\VC\crt\src\new.cpp gets called. All is good. However, in my opinion, my implementations of operator new does NOT overload the new in new.cpp, it CONFLICTS with it and violates the one-definition rule. Why doesn't the compiler complain about it? Or does the standard say since operator new is so special, one-definition rule does not apply here? Thanks.

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• Problems with variadic function

  - by morpheous

  I have the following function from some legacy code that I am maintaining. long getMaxStart(long start, long count, const myStruct *s1, ...) { long i1, maxstart; myStruct *s2; va_list marker; maxstart = start; /*BUGFIX: 003 */ /*(va_start(marker, count);*/ va_start(marker, s1); for (i1 = 1; i1 <= count; i1++) { s2 = va_arg(marker, myStruct *); /* <- s2 is assigned null here */ maxstart = MAX(maxstart, s2->firstvalid); /* <- SEGV here */ } va_end(marker); return (maxstart); } When the function is called with only one myStruct argument, it causes a SEGV. The code compiled and run without crashing on Windows XP when I compiled it using VS2005. I have now moved the code to Ubuntu Karmic and I am having problems with the stricter compiler on Linux. Is anyone able to spot what is causing the parameter not to be read correctly in the var_arg() statement? I am compiling using gcc version 4.4.1 Edit The statement that causes the SEGV is this one: start = getMaxStart(start, 1, ms1); The variables 'start' and 'ms1' have valid values when the code execution first reaches this line.

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• Sharepoint fails to load a C++ dll on windows 2008

  - by Nathan

  I have a sharepoint DLL that does some licensing things and as part of the code it uses an external C++ DLL to get the serial number of the hardisk. When i run this application on windows server 2003 it works fine, but on 2008 the whole site (loaded on load) crashes and resets continually. This is not 2008 R2 and is the same in 64 or 32 bits. If i put a debugger.break before the dll execution then I see the code get to the point of the break then never come back into the dll again. I do get some debug assertion warnings from within the function, again only in 2008, but im not sure this is related. I created a console app that runs the c# dll, which in turn loads the c++ dll, and this works perfectly on 2008 (although does show the assertion errors, but I have suppressed these now). The assertion errors are not in my code but within ICtypes.c and not something I can debug. If i put a breakpoint in the DLL it is never hit and the compiler says : "step in: Stepping over non user code" if i try to debug into the DLL using VS. I have tried wrapping the code used to call the DLL in: SPSecurity.RunWithElevatedPrivileges(delegate() but this also does not help. I have the sourcecode for this DLL so that is not a problem. If i delete the DLL from the directory I get an error about a missing DLL, if i replace it back to no error or warning just a complete failure. If i replace this code with a hardcoded string the whole application works fine. Any advice would be much appreciated, I can't understand why it works as a console app yet not when run by sharepoint, this is with the same user account, on the same machine... This is the code used to call the DLL: [DllImport("idDll.dll", EntryPoint = "GetMachineId", SetLastError = true)] extern static string GetComponentId([MarshalAs(UnmanagedType.LPStr)]String s); public static string GetComponentId() { Debugger.Break(); if (_machine == string.Empty) { string temp = ""; id= ComponentId.GetComponentId(temp); } return id; }

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