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• How to keep track of call statistics? C++

  - by tf.rz

  I'm working on a project that delivers statistics to the user. I created a class called Dog, And it has several functions. Speak, woof, run, fetch, etc. I want to have a function that spits out how many times each function has been called. I'm also interested in the constructor calls and destructor calls as well. I have a header file which defines all the functions, then a separate .cc file that implements them. My question is, is there a way to keep track of how many times each function is called? I have a function called print that will fetch the "statistics" and then output them to standard output. I was considering using static integers as part of the class itself, declaring several integers to keep track of those things. I know the compiler will create a copy of the integer and initialize it to a minimum value, and then I'll increment the integers in the .cc functions. I also thought about having static integers as a global variable in the .cc. Which way is easier? Or is there a better way to do this? Any help is greatly appreciated!

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• Creating serializeable unique compile-time identifiers for arbitrary UDT's.

  - by Endiannes

  I would like a generic way to create unique compile-time identifiers for any C++ user defined types. for example: unique_id<my_type>::value == 0 // true unique_id<other_type>::value == 1 // true I've managed to implement something like this using preprocessor meta programming, the problem is, serialization is not consistent. For instance if the class template unique_id is instantiated with other_type first, then any serialization in previous revisions of my program will be invalidated. I've searched for solutions to this problem, and found several ways to implement this with non-consistent serialization if the unique values are compile-time constants. If RTTI or similar methods, like boost::sp_typeinfo are used, then the unique values are obviously not compile-time constants and extra overhead is present. An ad-hoc solution to this problem would be, instantiating all of the unique_id's in a separate header in the correct order, but this causes additional maintenance and boilerplate code, which is not different than using an enum unique_id{my_type, other_type};. A good solution to this problem would be using user-defined literals, unfortunately, as far as I know, no compiler supports them at this moment. The syntax would be 'my_type'_id; 'other_type'_id; with udl's. I'm hoping somebody knows a trick that allows implementing serialize-able unique identifiers in C++ with the current standard (C++03/C++0x), I would be happy if it works with the latest stable MSVC and GNU-G++ compilers, although I expect if there is a solution, it's not portable.

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• C++ : integer constant is too large for its type

  - by user38586

  I need to bruteforce a year for an exercise. The compiler keep throwing this error: bruteforceJS12.cpp:8:28: warning: integer constant is too large for its type [enabled by default] My code is: #include <iostream> using namespace std; int main(){ unsigned long long year(0); unsigned long long result(318338237039211050000); unsigned long long pass(1337); while (pass != result) { for (unsigned long long i = 1; i<= year; i++) { pass += year * i * year; } cout << "pass not cracked with year = " << year << endl; ++year; } cout << "pass cracked with year = " << year << endl; } Note that I already tried with unsigned long long result(318338237039211050000ULL); I'm using gcc version 4.8.1 EDIT: Here is the corrected version using InfInt library http://code.google.com/p/infint/ #include <iostream> #include "InfInt.h" using namespace std; int main(){ InfInt year = "113"; InfInt result = "318338237039211050000"; InfInt pass= "1337"; while (pass != result) { for (InfInt i = 1; i<= year; i++) { pass += year * i * year; } cout << "year = " << year << " pass = " << pass << endl; ++year; } cout << "pass cracked with year = " << year << endl; }

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• C++ template type deduction problem

  - by hamishmcn

  motivation: I would like to create a utility class so that instead of having to write: if( someVal == val1 || someVal == val2 || someVal == val3 ) I could instead write: if( is(someVal).in(val1, val2, val3) ) which is much closer to the mathematical 'a is an element of (b,c,d)' and also would save on a lot of typing when the variable name 'someVal' is long. Here is the code I have so far (for 2 and 3 values): template<class T> class is { private: T t_; public: is(T t) : t_(t) { } bool in(const T& v1, const T& v2) { return t_ == v1 || t_ == v2; } bool in(const T& v1, const T& v2, const T& v3) { return t_ == v1 || t_ == v2 || t_ == v3; } }; However it fails to compile if I write: is(1).in(3,4,5); instead I have to write is<int>(1).in(3,4,5); Which isn't too bad, but it would be better if somehow the compiler could figure out that the type is int with out me having to explicitly specify it. Is there anyway to do this or I am stuck with specifying it explicitly?

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• Is it not possible to make a C++ application "Crash Proof"?

  - by Enno Shioji

  Let's say we have an SDK in C++ that accepts some binary data (like a picture) and does something. Is it not possible to make this SDK "crash-proof"? By crash I primarily mean forceful termination by the OS upon memory access violation, due to invalid input passed by the user (like an abnormally short junk data). I have no experience with C++, but when I googled, I found several means that sounded like a solution (use a vector instead of an array, configure the compiler so that automatic bounds check is performed, etc.). When I presented this to the developer, he said it is still not possible.. Not that I don't believe him, but if so, how is language like Java handling this? I thought the JVM performs everytime a bounds check. If so, why can't one do the same thing in C++ manually? UPDATE By "Crash proof" I don't mean that the application does not terminate. I mean it should not abruptly terminate without information of what happened (I mean it will dump core etc., but is it not possible to display a message like "Argument x was not valid" etc.?)

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• Debug.Assert-s use the same error message. Should I promote it to a static variable?

  - by Hamish Grubijan

  I love Asserts and code readability but not code duplication, and in several places I use a Debug.Assert which checks for the same condition like so: Debug.Assert(kosherBaconList.SelectedIndex != -1, "An error message along the lines - you should not ever be able to click on edit button without selecting a kosher bacon first."); This is in response to an actual bug, although the actual list does not contain kosher bacon. Anyhow, I can think of two approaches: private static readonly mustSelectKosherBaconBeforeEditAssertMessage = "An error message along the lines - you should not ever be able to " + "click on edit button without selecting a something first."; ... Debug.Assert( kosherBaconList.SelectedIndex != -1, mustSelectKosherBaconBeforeEditAssertMessage) or: if (kosherBaconList.SelectedIndex == -1) { AssertMustSelectKosherBaconBeforeEdit(); } ... [Conditional("DEBUG")] private void AssertMustSelectKosherBaconBeforeEdit() { // Compiler will optimize away this variable. string errorMessage = "An error message along the lines - you should not ever be able to " + "click on edit button without selecting a something first."; Debug.Assert(false, errorMessage); } or is there a third way which sucks less than either one above? Please share. General helpful relevant tips are also welcome.

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• OpenSceneGraph C++ Access Violation reading location 0x00421000

  - by Kobojunkie

  Working with OpenSceneGraph, and I keep running into this violation issue that I would appreciate some help with. The problem is with the particular line below which happens to be the first in my main function. osg::ref_ptr<osg::Node> bench = osgDB::readNodeFile("Models/test.IVE"); I have my models folder right in my directory. The error is as below. Unhandled exception at 0x68630A6C (msvcr100.dll) in OSG3D.exe: 0xC0000005: Access violation reading location 0x00421000. And this is where the problem seems to be coming up. /** Read an osg::Node from file. * Return valid osg::Node on success, * return NULL on failure. * The osgDB::Registry is used to load the appropriate ReaderWriter plugin * for the filename extension, and this plugin then handles the request * to read the specified file.*/ inline osg::Node* readNodeFile(const std::string& filename) { return readNodeFile(filename,Registry::instance()->getOptions()); } I would appreciate details on how best to tackle this kind of exception message in the future. Are there tools that make this easy to debug or are there ways to capture the exact issues and fix them? I would appreciate any help with this. My ultimate goal is to learn how to better debug C++ related issues please. With this, it means reading through the compiler error list http://msdn.microsoft.com/en-us/library/850cstw1(v=vs.71).aspx is not enough

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• make arm architecture c library in mac

  - by gamegamelife

  I'm trying to make my own c library in Mac and include it to my iphone program. The c code is simple , like this: math.h: int myPow2(int); math.c: #include "math.h" int myPow2(int num) { return num*num; } I search how to make the c library file ( .a or .lib ..etc) seems need to use gcc compiler (Is there other methods?) so I use this command: gcc -c math.c -o math.o ar rcs libmath.a math.o And include it in iPhone Project. Now it has the problem when build xcode iphone project. "file was built for unsupported file format which is not the architecture being linked" I found some pages discuss about the problem, but no detail how to make the i386/arm architecture library. And I finally use this command to do it: gcc -arch i386 -c math.c -o math.o /Developer/Platforms/iPhoneOS.platform/Developer/usr/bin/arm-apple-darwin10-gcc-4.2.1 -c math.c -o math.o I dont know if this method is correct? Or there has another method to do it?

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• Porting Perl to C++ `print "\x{2501}" x 12;`

  - by jippie

  I am porting a program from Perl to C++ as a learning objective. I arrived at a routine that draws a table with commands like the following: Perl: print "\x{2501}" x 12; And it draws 12 times a '?' ("box drawings heavy horizontal"). Now I figured out part of the problem already: Perl: \x{}, \x00 Hexadecimal escape sequence; C++: \unnnn To print a single Unicode character: C++: printf( "\u250f\n" ); But does C++ have a smart equivalent for the 'x' operator or would it come down to a for loop? UPDATE Let me include the full source code I am trying to compile with the proposed solution. The compiler does throw an errors: g++ -Wall -Werror project.cpp -o project project.cpp: In function ‘int main(int, char**)’: project.cpp:38:3: error: ‘string’ is not a member of ‘std’ project.cpp:38:15: error: expected ‘;’ before ‘s’ project.cpp:39:3: error: ‘cout’ is not a member of ‘std’ project.cpp:39:16: error: ‘s’ was not declared in this scope #include <stdlib.h> #include <stdint.h> #include <stdio.h> #include <string.h> int main ( int argc, char *argv[] ) { if ( argc != 2 ) { fprintf( stderr , "usage: %s matrix\n", argv[0] ); exit( 2 ); } else { //std::string s(12, "\u250f" ); std::string s(12, "u" ); std::cout << s; } }

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• What does an object look like in memory?

  - by NeilMonday

  This is probably a really dumb question, but I will ask anyway. I am curious what an object looks like in memory. Obviously it would have to have all of its member data in it. I assume that functions for an object would not be duplicated in memory (or maybe I am wrong?). It would seem wasteful to have 999 objects in memory all with the same function defined over and over. If there is only 1 function in memory for all 999 objects, then how does each function know who's member data to modify (I specifically want to know at the low level). Is there an object pointer that gets sent to the function behind the scenes? Perhaps it is different for every compiler? Also, how does the static keyword affect this? With static member data, I would think that all 999 objects would use the exact same memory location for their static member data. Where does this get stored? Static functions I guess would also just be one place in memory, and would not have to interact with instantiated objects, which I think I understand.

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• Automating Excel through the PIA makes VBA go squiffy.

  - by Jon Artus

  I have absolutely no idea how to start diagnosing this, and just wondered if anyone had any suggestions. I'm generating an Excel spreadsheet by calling some Macros from a C# application, and during the generation process it somehow breaks. I've got a VBA class containing all of my logging/error-handling logic, which I instantiate using a singleton-esque accessor, shown here: Private mcAppFramework As csys_ApplicationFramework Public Function AppFramework() As csys_ApplicationFramework If mcAppFramework Is Nothing Then Set mcAppFramework = New csys_ApplicationFramework Call mcAppFramework.bInitialise End If Set AppFramework = mcAppFramework End Function The above code works fine before I've generated the spreadsheet, but afterwards fails. The problem seems to be the following line; Set mcAppFramework = New csys_ApplicationFramework which I've never seen fail before. If I add a watch to the variable being assigned here, the type shows as csys_ApplicationFramework/wksFoo, where wksFoo is a random worksheet in the same workbook. What seems to be happening is that while the variable is of the right type, rather than filling that slot with a new instance of my framework class, it's making it point to an existing worksheet instead, the equivalent of Set mcAppFramework = wksFoo which is a compiler error, as one might expect. Even more bizarrely, if I put a breakpoint on the offending line, edit the line, and then resume execution, it works. For example, I delete the word 'New' move off the line, move back, re-type 'New' and resume execution. This somehow 'fixes' the workbook and it works happily ever after, with the type of the variable in my watch window showing as csys_ApplicationFramework/csys_ApplicationFramework as I'd expect. This implies that manipulating the workbook through the PIA is somehow breaking it temporarily. All I'm doing in the PIA is opening the workbook, calling several macros using Excel.Application.Run(), and saving it again. I can post a few more details if anyone thinks that it's relevant. I don't know how VBA creates objects behind the scenes or how to debug this. I also don't know how the way the code executes can change without the code itself changing. As previously mentioned, VBA has frankly gone a bit squiffy on me... Any thoughts?

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• C preprocessor problem in Microsoft Visual Studio 2010

  - by Remo.D

  I've encountered a problem with the new Visual C++ in VS 2010. I've got a header with the following defines: #define STC(y) #y #define STR(y) STC(\y) #define NUM(y) 0##y The intent is that you can have some constant around like #define TOKEN x5A and then you can have the token as a number or as a string: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\x5A" This is the expected behavior under the the substitution rules of macros arguments and so far it has worked well with gcc, open watcom, pellesC (lcc), Digital Mars C and Visual C++ in VS2008 Express. Today I recompiled the library with VS2010 Express only to discover that it doesn't work anymore! Using the new version I would get: NUM(TOKEN) -> 0x5A STR(TOKEN) -> "\y" It seems that the new preprocessor treats \y as an escape sequence even within a macro body which is a non-sense as escape sequences only have a meaning in literal strings. I suspect this is a gray area of the ANSI standard but even if the original behavior was mandated by the standard, MS VC++ is not exactly famous to be 100% ANSI C compliant so I guess I'll have to live with the new behavior of the MS compiler. Given that, does anybody have a suggestion on how to re-implement the original macros behavior with VS2010?

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• Why do I get "request for member in something not a struct or union" from this code?

  - by pyroxene

  I'm trying to teach myself C by coding up a linked list. I'm new to pointers and memory management and I'm getting a bit confused. I have this code: /* Remove a node from the list and rejiggle the pointers */ void rm_node(struct node **listP, int index) { struct node *prev; struct node *n = *listP; if (index == 0) { *listP = *listP->next; free(n); return; } for (index; index > 0; index--) { n = n->next; if (index == 2) { prev = n; } } prev->next = n->next; free(n); } to remove an element from the list. If I want to remove the first node, I still need some way of referring to the list, which is why the listP arg is a double pointer, so it can point to the first element of the list and allow me to free the node that used to be the head. However, when I try to dereference listP to access the pointer to the next node, the compiler tells me error: request for member ‘next’ in something not a structure or union . What am I doing wrong here? I think I might be hopelessly mixed up..?

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• Optimization of a c++ matrix/bitmap class

  - by Andrew

  I am searching a 2D matrix (or bitmap) class which is flexible but also fast element access. The contents A flexible class should allow you to choose dimensions during runtime, and would look something like this (simplified): class Matrix { public: Matrix(int w, int h) : data(new int[x*y]), width(w) {} void SetElement(int x, int y, int val) { data[x+y*width] = val; } // ... private: // symbols int width; int* data; }; A faster often proposed solution using templates is (simplified): template <int W, int H> class TMatrix { TMatrix() data(new int[W*H]) {} void SetElement(int x, int y, int val) { data[x+y*W] = val; } private: int* data; }; This is faster as the width can be "inlined" in the code. The first solution does not do this. However this is not very flexible anymore, as you can't change the size anymore at runtime. So my question is: Is there a possibility to tell the compiler to generate faster code (like when using the template solution), when the size in the code is fixed and generate flexible code when its runtime dependend? I tried to achieve this by writing "const" where ever possible. I tried it with gcc and VS2005, but no success. This kind of optimization would be useful for many other similar cases.

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• GetLongPathName Undeclared

  - by iwizardpro

  When I try to compile my code with the function GetLongPathName(), the compiler tells me that the function is undeclared. I have already read the MSDN documentation located @ http://msdn.microsoft.com/en-us/library/aa364980%28VS.85%29.aspx. But, even though I included those header files, I am still getting the undeclared function error. Which header file(s) am I supposed to include when using the function? #include <Windows.h> #include <WinBase.h> #define DLLEXPORT extern "C" __declspec(dllexport) DLLEXPORT char* file_get_long(char* path_original) { long length = 0; TCHAR* buffer = NULL; if(!path_original) { return "-10"; } length = GetLongPathName(path_original, NULL, 0); if(length == 0) { return "-10"; } buffer = new TCHAR[length]; length = GetLongPathName(path_original, buffer, length); if(length == 0) { return "-10"; } return buffer; } And, if it makes a difference, I am currently compiling using Dev-C++ on a Windows Vista 64-bit.

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• Why it's can be compiled in GNU/C++, can't compiled in VC++2010 RTM?

  - by volnet

  #include #include #include #include "copy_of_auto_ptr.h" #ifdef _MSC_VER #pragma message("#include ") #include // http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html#Diagnostic-Pragmas #endif /* case 1-4 is the requirement of the auto_ptr. which form http://ptgmedia.pearsoncmg.com/images/020163371X/autoptrupdate/auto_ptr_update.html */ /* case 1. (1) Direct-initialization, same type, e.g. */ std::auto_ptr source_int() { // return std::auto_ptr(new int(3)); std::auto_ptr tmp(new int(3)); return tmp; } /* case 2. (2) Copy-initialization, same type, e.g. */ void sink_int(std::auto_ptr p) { std::cout source_derived() { // return std::auto_ptr(new Derived()); std::auto_ptr tmp(new Derived()); return tmp; } /* case 4. (4) Copy-initialization, base-from-derived, e.g. */ void sink_base( std::auto_ptr p) { p-go(); } int main(void) { /* // auto_ptr */ // case 1. // auto_ptr std::auto_ptr p_int(source_int()); std::cout p_derived(source_derived()); p_derived-go(); // case 4. // auto_ptr sink_base(source_derived()); return 0; } In Eclipse(GNU C++.exe -v gcc version 3.4.5 (mingw-vista special r3)) it's two compile error: Description Resource Path Location Type initializing argument 1 of void sink_base(std::auto_ptr<Base>)' from result ofstd::auto_ptr<_Tp::operator std::auto_ptr<_Tp1() [with _Tp1 = Base, _Tp = Derived]' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem Description Resource Path Location Type no matching function for call to `std::auto_ptr::auto_ptr(std::auto_ptr)' auto_ptr_ref_research.cpp auto_ptr_ref_research/auto_ptr_ref_research 190 C/C++ Problem But it's right in VS2010 RTM. Questions: Which compiler stand for the ISO C++ standard? The content of case 4 is the problem "auto_ptr & auto_ptr_ref want to resolve?"

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• Holding variables in memory, C++

  - by b-gen-jack-o-neill

  Today something strange came to my mind. When I want to hold some string in C (C++) the old way, without using string header, I just create array and store that string into it. But, I read that any variable definition in C in local scope of function ends up in pushing these values onto the stack. So, the string is actually 2* bigger than needed. Because first, the push instructions are located in memory, but then when they are executed (pushed onto the stack) another "copy" of the string is created. First the push instructions, than the stack space is used for one string. So, why is it this way? Why doesn't compiler just add the string (or other variables) to the program instead of creating them once again when executed? Yes, I know you cannot just have some data inside program block, but it could just be attached to the end of the program, with some jump instruction before. And than, we would just point to these data? Because they are stored in RAM when the program is executed. Thanks.

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• Function returning pointer to struct

  - by GammaGuy

  I am having some issues with code that is returning a pointer to a struct declared inside a class. Here is my code so far: SortedList.h #ifndef SORTEDLIST_H #define SORTEDLIST_H class SortedList{ public: SortedList(); ... private: struct Listnode { Student *student; Listnode *next; }; static Listnode *copyList (Listnode *L); }; #endif SortedList.cpp #include "SortedList.h" ... // Here is where the problem lies Listnode SortedList::*copyList(Listnode *L) { return 0; // for NULL } Apparently, the copy list method wont compile. I am using Microsoft Visual Studio and the compiler tells me that "Listnode" is unidentified. When I try to compile, here is whhat I get: 1>------ Build started: Project: Program3, Configuration: Debug Win32 ------ 1> SortedList.cpp 1>c:\users\owner\documents\college\fall 2012\cs 368 - learn c++\program3\program3\sortedlist.cpp(159): error C2657: 'SortedList::*' found at the start of a statement (did you forget to specify a type?) 1>c:\users\owner\documents\college\fall 2012\cs 368 - learn c++\program3\program3\sortedlist.cpp(159): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>c:\users\owner\documents\college\fall 2012\cs 368 - learn c++\program3\program3\sortedlist.cpp(159): error C2065: 'L' : undeclared identifier 1>c:\users\owner\documents\college\fall 2012\cs 368 - learn c++\program3\program3\sortedlist.cpp(159): error C4430: missing type specifier - int assumed. Note: C++ does not support default-int 1>c:\users\owner\documents\college\fall 2012\cs 368 - learn c++\program3\program3\sortedlist.cpp(159): fatal error C1903: unable to recover from previous error(s); stopping compilation ========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ========== Help would be greatly appreciated...ASAP

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• [c++] accessing the hidden 'this' pointer

  - by Kyle

  I have a GUI architecture wherein elements fire events like so: guiManager->fireEvent(BUTTON_CLICKED, this); Every single event fired passes 'this' as the caller of the event. There is never a time I dont want to pass 'this', and further, no pointer except for 'this' should ever be passed. This brings me to a problem: How can I assert that fireEvent is never given a pointer other than 'this', and how can I simplify (and homogenize) calls to fireEvent to just: guiManager->fireEvent(BUTTON_CLICKED); At this point, I'm reminded of a fairly common compiler error when you write something like this: class A { public: void foo() {} }; class B { void oops() { const A* a = new A; a->foo(); } }; int main() { return 0; } Compiling this will give you ../src/sandbox.cpp: In member function ‘void B::oops()’: ../src/sandbox.cpp:7: error: passing ‘const A’ as ‘this’ argument of ‘void A::foo()’ discards qualifiers because member functions pass 'this' as a hidden parameter. "Aha!" I say. This (no pun intended) is exactly what I want. If I could somehow access the hidden 'this' pointer, it would solve both issues I mentioned earlier. The problem is, as far as I know you can't (can you?) and if you could, there would be outcries of "but it would break encapsulation!" Except I'm already passing 'this' every time, so what more could it break. So, is there a way to access the hidden 'this', and if not are there any idioms or alternative approaches that are more elegant than passing 'this' every time?

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• C++ templates error: instantiated from 'void TestClass::testMethod(T, std::map) [with T = SomeClass]

  - by pureconsciousness

  Hello there, I've some problem in my code I cannot deal with: #ifndef TESTCLASS_H_ #define TESTCLASS_H_' #include <map> using namespace std; template <typename T> class TestClass { public: TestClass(){}; virtual ~TestClass(){}; void testMethod(T b,std::map<T,int> m); }; template <typename T> void TestClass`<T`>::testMethod(T b,std::map<T,int> m){ m[b]=0; } #endif /*TESTCLASS_H_*/ int main(int argc, char* argv[]) { SomeClass s; TestClass<SomeClass> t; map<SomeClass,int> m; t.testMethod(s,m); } Compiler gives me following error in line m[b]=0; : instantiated from 'void TestClass::testMethod(T, std::map) [with T = SomeClass] Could you help find the problem?? Thanks in advance

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• C++ privately contructed class

  - by Nona Urbiz

  How can I call a function and keep my constructor private? If I make the class static, I need to declare an object name which the compiler uses to call the constructor, which it cannot if the constructor is private (also the object would be extraneous). Here is the code I am attempting to use (it is not compilable): I want to keep the constructor private because I will later be doing a lot of checks before adding an object, modifying previous objects when all submitted variables are not unique rather than creating new objects. #include <iostream> #include <fstream> #include <regex> #include <string> #include <list> #include <map> using namespace std; using namespace tr1; class Referral { public: string url; map<string, int> keywords; static bool submit(string url, string keyword, int occurrences) { //if(Referrals.all.size == 0){ // Referral(url, keyword, occurrences); //} } private: list<string> urls; Referral(string url, string keyword, int occurrences) { url = url; keywords[keyword] = occurrences; Referrals.all.push_back(this); } }; struct All { list<Referral> all; }Referrals; int main() { Referral.submit("url", "keyword", 1); }

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• Python to C/C++ const char question

  - by tsukemonoki

  I am extending Python with some C++ code. One of the functions I'm using has the following signature: int PyArg_ParseTupleAndKeywords(PyObject *arg, PyObject *kwdict, char *format, char **kwlist, ...); (link: http://docs.python.org/release/1.5.2p2/ext/parseTupleAndKeywords.html) The parameter of interest is kwlist. In the link above, examples on how to use this function are given. In the examples, kwlist looks like: static char *kwlist[] = {"voltage", "state", "action", "type", NULL}; When I compile this using g++, I get the warning: warning: deprecated conversion from string constant to ‘char*’ So, I can change the static char* to a static const char*. Unfortunately, I can't change the Python code. So with this change, I get a different compilation error (can't convert char** to const char**). Based on what I've read here, I can turn on compiler flags to ignore the warning or I can cast each of the constant strings in the definition of kwlist to char *. Currently, I'm doing the latter. What are other solutions? Sorry if this question has been asked before. I'm new.

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• Visual Studio 2010 compile error with std::string?

  - by AJG85

  So this is possibly the strangest thing I've seen recently and was curious how this could happen. The compiler gave me an error saying that std::string is undefined when used as a return type but not when used as a parameter in methods of a class! #pragma once #include <string> #include <vector> // forward declarations class CLocalReference; class CResultSetHandle; class MyClass { public: MyClass() {} ~MyClass {} void Retrieve(const CLocalReference& id, CResultSetHandle& rsh, std::string& item); // this is fine const std::string Retrieve(const CLocalReference& id, CResultSetHandle& rsh); // this fails with std::string is undefined?!?! }; Doing a Rebuild All it still happened I had to choose clean solution and then Rebuild All again after for the universe to realign. While it's resolved for the moment I'd still like to know what could have caused this because I'm at a loss as to why when there should be no conflicts especially when I always use fully qualified names for STL.

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• Javascript int variable from ASP.NET MVC Model data?

  - by Anders Svensson

  I need to get model data into a javascript variable and use it as an int to compare values. But I can only figure out how to get the model data as strings, otherwise the compiler complains. So how can I get the max and taskBudgetHours as int variables in the Javascript? <script type="text/javascript"> $(document).ready(function () { $("#taskForm").submit(function (e) { var taskBudgetHours = $('#BudgetHours').val(); var max = '<%: Model.Project.RemainingBudgetHours %>'; var test = 'test'; alert(taskBudgetHours); alert(max); if (taskBudgetHours <= max) { //This doesn't work, seems to treat it as strings... return true; } else { //Prevent the submit event and remain on the screen e.preventDefault(); alert('There are only ' + max + ' hours left of the project hours.'); return false; } }); return; }); </script>

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• How can I compare the performance of log() and fp division in C++?

  - by Ventzi Zhechev

  Hi, I’m using a log-based class in C++ to store very small floating-point values (as the values otherwise go beyond the scope of double). As I’m performing a large number of multiplications, this has the added benefit of converting the multiplications to sums. However, at a certain point in my algorithm, I need to divide a standard double value by an integer value and than do a *= to a log-based value. I have overloaded the *= operator for my log-based class and the right-hand side value is first converted to a log-based value by running log() and than added to the left-hand side value. Thus the operations actually performed are floating-point division, log() and floating-point summation. My question whether it would be faster to first convert the denominator to a log-based value, which would replace the floating-point division with floating-point subtraction, yielding the following chain of operations: twice log(), floating-point subtraction, floating-point summation. In the end, this boils down to whether floating-point division is faster or slower than log(). I suspect that a common answer would be that this is compiler and architecture dependent, so I’ll say that I use gcc 4.2 from Apple on darwin 10.3.0. Still, I hope to get an answer with a general remark on the speed of these two operators and/or an idea on how to measure the difference myself, as there might be more going on here, e.g. executing the constructors that do the type conversion etc. Cheers!

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