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• C++ trouble with pointers to objects

  - by Zibd

  I have a class with a vector of pointers to objects. I've introduced some elements on this vector, and on my main file I've managed to print them and add others with no problems. Now I'm trying to remove an element from that vector and check to see if it's not NULL but it is not working. I'm filling it with on class Test: Other *a = new Other(1,1); Other *b = new Other(2,2); Other *c = new Other(3,3); v->push_back(a); v->push_back(b); v->push_back(c); And on my main file I have: Test t; (...) Other *pointer = t.vect->at(0); delete t.vect->at(0); t.vect->erase(t.vect->begin()); if (pointer == NULL) { cout << "Nothing here.."; } // Never enters here..

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• useer degined Copy ctor, and copy-ctors further down the chain - compiler bug ? programers brainbug

  - by J.Colmsee

  Hi. i have a little problem, and I am not sure if it's a compiler bug, or stupidity on my side. I have this struct : struct BulletFXData { int time_next_fx_counter; int next_fx_steps; Particle particles[2];//this is the interesting one ParticleManager::ParticleId particle_id[2]; }; The member "Particle particles[2]" has a self-made kind of smart-ptr in it (resource-counted texture-class). this smart-pointer has a default constructor, that initializes to the ptr to 0 (but that is not important) I also have another struct, containing the BulletFXData struct : struct BulletFX { BulletFXData data; BulletFXRenderFunPtr render_fun_ptr; BulletFXUpdateFunPtr update_fun_ptr; BulletFXExplosionFunPtr explode_fun_ptr; BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr; BulletFX( BulletFXData data, BulletFXRenderFunPtr render_fun_ptr, BulletFXUpdateFunPtr update_fun_ptr, BulletFXExplosionFunPtr explode_fun_ptr, BulletFXLifetimeOverFunPtr lifetime_over_fun_ptr) :data(data), render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } /* //USER DEFINED copy-ctor. if it's defined things go crazy BulletFX(const BulletFX& rhs) :data(data),//this line of code seems to do a plain memory-copy without calling the right ctors render_fun_ptr(render_fun_ptr), update_fun_ptr(update_fun_ptr), explode_fun_ptr(explode_fun_ptr), lifetime_over_fun_ptr(lifetime_over_fun_ptr) { } */ }; If i use the user-defined copy-ctor my smart-pointer class goes crazy, and it seems that calling the CopyCtor / assignment operator aren't called as they should. So - does this all make sense ? it seems as if my own copy-ctor of struct BulletFX should do exactly what the compiler-generated would, but it seems to forget to call the right constructors down the chain. compiler bug ? me being stupid ? Sorry about the big code, some small example could have illustrated too. but often you guys ask for the real code, so well - here it is :D

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• GetIpAddrTable() leaks memory. How to resolve that?

  - by Stabledog

  On my Windows 7 box, this simple program causes the memory use of the application to creep up continuously, with no upper bound. I've stripped out everything non-essential, and it seems clear that the culprit is the Microsoft Iphlpapi function "GetIpAddrTable()". On each call, it leaks some memory. In a loop (e.g. checking for changes to the network interface list), it is unsustainable. There seems to be no async notification API which could do this job, so now I'm faced with possibly having to isolate this logic into a separate process and recycle the process periodically -- an ugly solution. Any ideas? // IphlpLeak.cpp - demonstrates that GetIpAddrTable leaks memory internally: run this and watch // the memory use of the app climb up continuously with no upper bound. #include <stdio.h> #include <windows.h> #include <assert.h> #include <Iphlpapi.h> #pragma comment(lib,"Iphlpapi.lib") void testLeak() { static unsigned char buf[16384]; DWORD dwSize(sizeof(buf)); if (GetIpAddrTable((PMIB_IPADDRTABLE)buf, &dwSize, false) == ERROR_INSUFFICIENT_BUFFER) { assert(0); // we never hit this branch. return; } } int main(int argc, char* argv[]) { for ( int i = 0; true; i++ ) { testLeak(); printf("i=%d\n",i); Sleep(1000); } return 0; }

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• Prog error: for replacing spaces with "%20"

  - by assasinC

  below is the prog i am compiling for replacing spaces with "%20" but when I run it output window shows blank and a message "arrays5.exe has occurred a prob" #include <iostream> #include<cstring> using namespace std; void method(char str[], int len) //replaces spaces with "%20" { int spaces, newlen,i; for (i=0;i<len;i++) if(str[i]==' ') spaces++; newlen=len+spaces*2; str[newlen]=0; for (i=len-1;i>=0;i--) { if(str[i]==' ') { str[newlen-1]='0'; str[newlen-2]='2'; str[newlen-3]='%'; newlen=newlen-3; } else { str[newlen-1]=str[i]; newlen=newlen-1; } } } int main() { char str[20]="sa h "; method(str,5); cout <<str<<endl; return 0; } Please help me finding the error.Thanks

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• C++ 64bit issue

  - by Bobby

  I have the following code: tmp_data = simulated_data[index_data]; unsigned char *dem_content_buff; dem_content_buff = new unsigned char [dem_content_buff_size]; int tmp_data; unsigned long long tmp_64_data; if (!(strcmp(dems[i].GetValType(), "s32"))) { dem_content_buff[BytFldPos] = tmp_data; dem_content_buff[BytFldPos + 1] = tmp_data >> 8; dem_content_buff[BytFldPos + 2] = tmp_data >> 16; dem_content_buff[BytFldPos + 3] = tmp_data >> 24; } if (!(strcmp(dems[i].GetValType(), "f64"))) { dem_content_buff[BytFldPos] = tmp_data; dem_content_buff[BytFldPos + 1] = tmp_data >> 8; dem_content_buff[BytFldPos + 2] = tmp_data >> 16; dem_content_buff[BytFldPos + 3] = tmp_data >> 24; dem_content_buff[BytFldPos + 4] = tmp_data >> 32; dem_content_buff[BytFldPos + 5] = tmp_data >> 40; dem_content_buff[BytFldPos + 6] = tmp_data >> 48; dem_content_buff[BytFldPos + 7] = tmp_data >> 56; } I am getting some weird memory errors in other places of the application when the second if statement is true and executed. When I comment out the 2nd if statement, the problem works fine. So I suspect the way I am performing bitwise operations for 64bit data is incorrect. Can anyone see anything in this code that needs to be corrected?

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• Evaluate an expression tree

  - by Phronima

  Hi, This project that I'm working on requires that an expression tree be constructed from a string of single digit operands and operators both represented as type char. I did the implmentation and the program up to that point works fine. I'm able to print out the inorder, preorder and postorder traversals in the correct way. The last part calls for evaulating the expression tree. The parameters are an expression tree "t" and its root "root". The expression tree is ((3+2)+(6+2)) which is equal to 13. Instead I get 11 as the answer. Clearly I'm missing something here and I've done everything short of bashing my head against the desk. I would greatly appreciate it if someone can point me in the right direction. (Note that at this point I'm only testing addition and will add in the other operators when I get this method working.) public int evalExpression( LinkedBinaryTree t, BTNode root ) { if( t.isInternal( root ) ) { int x = 0, y = 0, value = 0; char operator = root.element(); if( root.getLeft() != null ) x = evalExpression(t, t.left( root ) ); if( root.getRight() != null ) y = evalExpression(t, t.right( root ) ); if( operator == '+' ) { value = value + Character.getNumericValue(x) + Character.getNumericValue(y); } return value; } else { return root.element(); } }

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• overloading "<<" with a struct (no class) cout style

  - by monkeyking

  I have a struct that I'd like to output using either 'std::cout' or some other output stream. Is this possible without using classes? Thanks #include <iostream> #include <fstream> template <typename T> struct point{ T x; T y; }; template <typename T> std::ostream& dump(std::ostream &o,point<T> p) const{ o<<"x: " << p.x <<"\ty: " << p.y <<std::endl; } template<typename T> std::ostream& operator << (std::ostream &o,const point<T> &a){ return dump(o,a); } int main(){ point<double> p; p.x=0.1; p.y=0.3; dump(std::cout,p); std::cout << p ;//how? return 0; } I tried different syntax' but I cant seem to make it work.

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• VC9 C1083 Cannot open include file: 'boost...' after trying to abstract an include dependency

  - by ronivek

  Hey, So I've been working on a project for the past number of weeks and it uses a number of Boost libraries. In particular I'm using the boost::dynamic_bitset library quite extensively. I've had zero issues up until now; but tonight I discovered a dependency between some includes which I had to resolve; and I tried to do so by providing an abstract callback class. Effectively I now have the following: First include... class OtherClassCallback { public: virtual int someOtherMethod() const = 0; }; class SomeClass { public: void someMethod(OtherClassCallback *oc) { ... oc->someOtherMethod(); ... } }; Second include... #include "SomeClass.h" class SomeOtherClass : public OtherClassCallback { public: int someOtherMethod() const { return this->someInt; } }; Here is the issue; ever since I implemented this class I'm now getting the following error: fatal error C1083: Cannot open include file: 'boost/dynamic_bitset/dynamic_bitset.hpp': No such file or directory Now I'm getting no other compiler errors; and it's a pretty substantial project. My include paths and so on are perfect; my files are fully accessible and removing the changes fixes the issue. Does anyone have any idea what might be going on? I'm compiling to native Windows executables in VS9. I should confess that I'm very inexperienced with C++ in general so go easy on me if it's something horribly straightforward; I can't figure it out.

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• C++ design question, container of instances and pointers

  - by Tom

  Hi all, Im wondering something. I have class Polygon, which composes a vector of Line (another class here) class Polygon { std::vector<Line> lines; public: const_iterator begin() const; const_iterator end() const; } On the other hand, I have a function, that calculates a vector of pointers to lines, and based on those lines, should return a pointer to a Polygon. Polygon* foo(Polygon& p){ std::vector<Line> lines = bar (p.begin(),p.end()); return new Polygon(lines); } Here's the question: I can always add a Polygon (vector Is there a better way that dereferencing each element of the vector and assigning it to the existing vector container? //for line in vector<Line*> v //vcopy is an instance of vector<Line> vcopy.push_back(*(v.at(i)) I think not, but I dont really like that approach. Hopefully, I will be able to convince the author of the class to change it, but I cant base my coding right now to that fact (and i'm scared of a performance hit). Thanks in advance.

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• C++ design question, container of instances and pointers

  - by Tom

  Hi all, Im wondering something. I have class Polygon, which composes a vector of Line (another class here) class Polygon { std::vector<Line> lines; public: const_iterator begin() const; const_iterator end() const; } On the other hand, I have a function, that calculates a vector of pointers to lines, and based on those lines, should return a pointer to a Polygon. Polygon* foo(Polygon& p){ std::vector<Line> lines = bar (p.begin(),p.end()); return new Polygon(lines); } Here's the question: I can always add a Polygon (vector Is there a better way that dereferencing each element of the vector and assigning it to the existing vector container? //for line in vector<Line*> v //vcopy is an instance of vector<Line> vcopy.push_back(*(v.at(i)) I think not, but I dont really like that approach. Hopefully, I will be able to convince the author of the class to change it, but I cant base my coding right now to that fact (and i'm scared of a performance hit). Thanks in advance.

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• C++ design question, container of instances and pointers

  - by Tom

  Hi all, Im wondering something. I have class Polygon, which composes a vector of Line (another class here) class Polygon { std::vector<Line> lines; public: const_iterator begin() const; const_iterator end() const; } On the other hand, I have a function, that calculates a vector of pointers to lines, and based on those lines, should return a pointer to a Polygon. Polygon* foo(Polygon& p){ std::vector<Line> lines = bar (p.begin(),p.end()); return new Polygon(lines); } Here's the question: I can always add a Polygon (vector Is there a better way that dereferencing each element of the vector and assigning it to the existing vector container? //for line in vector<Line*> v //vcopy is an instance of vector<Line> vcopy.push_back(*(v.at(i)) I think not, but I dont really like that approach. Hopefully, I will be able to convince the author of the class to change it, but I cant base my coding right now to that fact (and i'm scared of a performance hit). Thanks in advance.

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• SFINAE + sizeof = detect if expression compiles

  - by FredOverflow

  I just found out how to check if operator<< is provided for a type. template<class T> T& lvalue_of_type(); template<class T> T rvalue_of_type(); template<class T> struct is_printable { template<class U> static char test(char(*)[sizeof( lvalue_of_type<std::ostream>() << rvalue_of_type<U>() )]); template<class U> static long test(...); enum { value = 1 == sizeof test<T>(0) }; typedef boost::integral_constant<bool, value> type; }; Is this trick well-known, or have I just won the metaprogramming Nobel prize? ;) EDIT: I made the code simpler to understand and easier to adapt with two global function template declarations lvalue_of_type and rvalue_of_type.

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• c++ specialized overload?

  - by acidzombie24

  -edit- i am trying to close the question. i solved the problem with boost::is_base_and_derived In my class i want to do two things. 1) Copy int, floats and other normal values 2) Copy structs that supply a special copy function (template T copyAs(); } the struct MUST NOT return int's unless i explicitly say ints. I do not want the programmer mistaking the mistake by doing int a = thatClass; -edit- someone mention classes dont return anything, i mean using the operator Type() overload. How do i create my copy operator in such a way i can copy both 1) ints, floats etc and the the struct restricted in the way i mention in 2). i tried doing template <class T2> T operator = (const T2& v); which would cover my ints, floats etc. But how would it differentiate from structs? so i wrote T operator = (const SomeGenericBase& v); The idea was the GenericBase would be unsed instead then i can do v.Whatever. But that backfires bc the functions i want wouldnt exist, unless i use virtual, but virtual templates dont exist. Also i would hate to use virtual I think the solution is to get rid of ints and have it convert to something that can do .as(). So i wrote something up but now i have the same problem, how does that differentiate ints and structs that have the .as() function template?

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• How do I cover unintuitive code blocks?

  - by naivedeveloper

  For some reason, I'm having a hard time trying to cover the block of code below. This code is an excerpt from the UNIX uniq command. I'm trying to write test cases to cover all blocks, but can't seem to reach this block: if (nfiles == 2) { // Generic error routine } In context: int main (int argc, char **argv) { int optc = 0; bool posixly_correct = (getenv ("POSIXLY_CORRECT") != NULL); int nfiles = 0; char const *file[2]; file[0] = file[1] = "-"; program_name = argv[0]; skip_chars = 0; skip_fields = 0; check_chars = SIZE_MAX; for (;;) { /* Parse an operand with leading "+" as a file after "--" was seen; or if pedantic and a file was seen; or if not obsolete. */ if (optc == -1 || (posixly_correct && nfiles != 0) || ((optc = getopt_long (argc, argv, "-0123456789Dcdf:is:uw:", longopts, NULL)) == -1)) { if (optind == argc) break; if (nfiles == 2) { // Handle errors } file[nfiles++] = argv[optind++]; } else switch (optc) { case 1: { unsigned long int size; if (optarg[0] == '+' && posix2_version () < 200112 && xstrtoul (optarg, NULL, 10, &size, "") == LONGINT_OK && size <= SIZE_MAX) skip_chars = size; else if (nfiles == 2) { // Handle error } else file[nfiles++] = optarg; } break; } } } Any help would be greatly appreciated. Thanks.

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• Handling Apache Thrift list/map Return Types in C++

  - by initzero

  First off, I'll say I'm not the most competent C++ programmer, but I'm learning, and enjoying the power of Thrift. I've implemented a Thrift Service with some basic functions that return void, i32, and list. I'm using a Python client controlled by a Django web app to make RPC calls and it works pretty well. The generated code is pretty straight forward, except for list returns: namespace cpp Remote enum N_PROTO { N_TCP, N_UDP, N_ANY } service Rcon { i32 ping() i32 KillFlows() i32 RestartDispatch() i32 PrintActiveFlows() i32 PrintActiveListeners(1:i32 proto) list<string> ListAllFlows() } The generated signatures from Rcon.h: int32_t ping(); int32_t KillFlows(); int32_t RestartDispatch(); int32_t PrintActiveFlows(); int32_t PrintActiveListeners(const int32_t proto); int64_t ListenerBytesReceived(const int32_t id); void ListAllFlows(std::vector<std::string> & _return); As you see, the ListAllFlows() function generated takes a reference to a vector of strings. I guess I expect it to return a vector of strings as laid out in the .thrift description. I'm wondering if I am meant to provide the function a vector of strings to modify and then Thrift will handle returning it to my client despite the function returning void. I can find absolutely no resources or example usages of Thrift list< types in C++. Any guidance would be appreciated.

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• how to Clean up(destructor) a dynamic Array of pointers??

  - by Ahmed Sharara

  Is that Destructor is enough or do I have to iterate to delete the new nodes?? #include "stdafx.h" #include<iostream> using namespace std; struct node{ int row; int col; int value; node* next_in_row; node* next_in_col; }; class MultiLinkedListSparseArray { private: char *logfile; node** rowPtr; node** colPtr; // used in constructor node* find_node(node* out); node* ins_node(node* ins,int col); node* in_node(node* ins,node* z); node* get(node* in,int row,int col); bool exist(node* so,int row,int col); //add anything you need public: MultiLinkedListSparseArray(int rows, int cols); ~MultiLinkedListSparseArray(); void setCell(int row, int col, int value); int getCell(int row, int col); void display(); void log(char *s); void dump(); }; MultiLinkedListSparseArray::MultiLinkedListSparseArray(int rows,int cols){ rowPtr=new node* [rows+1]; colPtr=new node* [cols+1]; for(int n=0;n<=rows;n++) rowPtr[n]=NULL; for(int i=0;i<=cols;i++) colPtr[i]=NULL; } MultiLinkedListSparseArray::~MultiLinkedListSparseArray(){ // is that destructor enough?? cout<<"array is deleted"<<endl; delete [] rowPtr; delete [] colPtr; }

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• C++ Template problem adding two data types

  - by Sara

  I have a template class with an overloaded + operator. This is working fine when I am adding two ints or two doubles. How do I get it to add and int and a double and return the double? template <class T> class TemplateTest { private: T x; public: TemplateTest<T> operator+(const TemplateTest<T>& t1)const { return TemplateTest<T>(x + t1.x); } } in my main function i have void main() { TemplateTest intTt1 = TemplateTest<int>(2); TemplateTest intTt2 = TemplateTest<int>(4); TemplateTest doubleTt1 = TemplateTest<double>(2.1d); TemplateTest doubleTt2 = TemplateTest<double>(2.5d); std::cout << intTt1 + intTt2 << /n; std::cout << doubleTt1 + doubleTt2 << /n; } I want to be able to also do this std::cout << doubleTt1 + intTt2 << /n;

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• problem with converting simple code from Winform to silverlight app.

  - by Sara

  Hi. I have this code for window form application and I have been attempting to convert it to a Silverlight application but it does not work!. There is a Textbox and I attached KeyDown event handler to it. when the user press the arrow key ( left or right) while the focus on the textbox, it will write . or -. When it is window form i used e.KeyCode and Keys.Right and its works great but when it is silverlight I used e.Key and key.Right and the program doesn't work good because the arrows do the 2 functions moving and write ./-. How I can work this out in Silverlight? (My English not good) The code ( window form): private void textBox1_KeyDown(object sender, KeyEventArgs e) { if (sender is TextBox) { TextBox textBox = (TextBox)sender; if (e.KeyCode == Keys.Left || e.KeyCode == Keys.Right) { e.Handled = true; char insert; if (e.KeyCode == Keys.Left) { insert = '.'; } else { insert = '-'; } int i = textBox.SelectionStart; textBox.Text = textBox.Text.Insert(i, insert.ToString()); textBox.Select(i + 1, 0); } } } (and Silverlight): private void textBox1_KeyDown(object sender, KeyEventArgs e) { if (sender is TextBox) { TextBox textBox = (TextBox)sender; if (e.Key == Key.Left || e.Key == Key.Right) { e.Handled = true; char insert; if (e.Key == Key.Left) { insert = '.'; } else { insert = '-'; } int i = textBox.SelectionStart; textBox.Text = textBox.Text.Insert(i, insert.ToString()); textBox.Select(i + 1, 0); } } } I don't understand, is there huge different effect between using Keycode/Keys and Key/Key or because something else?

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• How to convert "0" and "1" to false and true

  - by Chris

  I have a method which is connecting to a database via Odbc. The stored procedure which I'm calling has a return value which from the database side is a 'Char'. Right now I'm grabbing that return value as a string and using it in a simple if statement. I really don't like the idea of comparing a string like this when only two values can come back from the database, 0 and 1. OdbcCommand fetchCommand = new OdbcCommand(storedProc, conn); fetchCommand.CommandType = CommandType.StoredProcedure; fetchCommand.Parameters.AddWithValue("@column ", myCustomParameter); fetchCommand.Parameters.Add("@myReturnValue", OdbcType.Char, 1). Direction = ParameterDirection.Output; fetchCommand.ExecuteNonQuery(); string returnValue = fetchCommand.Parameters["@myReturnValue"].Value.ToString(); if (returnValue == "1") { return true; } What would be the proper way to handle this situation. I've tried 'Convert.ToBoolean()' which seemed like the obvious answer but I ran into the 'String was not recognized as a valid Boolean. ' exception being thrown. Am I missing something here, or is there another way to make '1' and '0' act like true and false? Thanks!

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• Howcome some C++ functions with unspecified linkage build with C linkage?

  - by christoffer

  This is something that makes me fairly perplexed. I have a C++ file that implements a set of functions, and a header file that defines prototypes for them. When building with Visual Studio or MingW-gcc, I get linking errors on two of the functions, and adding an 'extern "C"' qualifier resolved the error. How is this possible? Header file, "some_header.h": // Definition of struct DEMO_GLOBAL_DATA omitted DWORD WINAPI ThreadFunction(LPVOID lpData); void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen); void CheckValid(DEMO_GLOBAL_DATA *pData); int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName); void HandleEnd(DEMO_GLOBAL_DATA *pData); C++ file, "some_implementation.cpp" #include "some_header.h" DWORD WINAPI ThreadFunction(LPVOID lpData) { /* omitted */ } void WriteLogString(void *pUserData, const char *pString, unsigned long nStringLen) { /* omitted */ } void CheckValid(DEMO_GLOBAL_DATA *pData) { /* omitted */ } int HandleStart(DEMO_GLOBAL_DATA * pDAta, TCHAR * pLogFileName) { /* omitted */ } void HandleEnd(DEMO_GLOBAL_DATA *pData) { /* omitted */ } The implementations compile without warnings, but when linking with the UI code that calls these, I get a normal error LNK2001: unresolved external symbol "int __cdecl HandleStart(struct _DEMO_GLOBAL_DATA *, wchar_t *) error LNK2001: unresolved external symbol "void __cdecl CheckValid(struct _DEMO_MAIN_GLOBAL_DATA * What really confuses me, now, is that only these two functions (HandleStart and CheckValid) seems to be built with C linkage. Explicitly adding "extern 'C'" declarations for only these two resolved the linking error, and the application builds and runs. Adding "extern 'C'" on some other function, such as HandleEnd, introduces a new linking error, so that one is obviously compiled correctly. The implementation file is never modified in any of this, only the prototypes.

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• typedef struct, circular dependency, forward definitions

  - by BlueChip

  The problem I have is a circular dependency issue in C header files ...Having looked around I suspect the solution will have something to do with Forward Definitions, but although there are many similar problems listed, none seem to offer the information I require to resolve this one... I have the following 5 source files: // fwd1.h #ifndef __FWD1_H #define __FWD1_H #include "fwd2.h" typedef struct Fwd1 { Fwd2 *f; } Fwd1; void fwd1 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD1_H . // fwd1.c #include "fwd1.h" #include "fwd2.h" void fwd1 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwd2.h #ifndef __FWD2_H #define __FWD2_H #include "fwd1.h" typedef struct Fwd2 { Fwd1 *f; } Fwd2; void fwd2 (Fwd1 *f1, Fwd2 *f2) ; #endif // __FWD2_H . // fwd2.c #include "fwd1.h" #include "fwd2.h" void fwd2 (Fwd1 *f1, Fwd2 *f2) { return; } . // fwdMain.c #include "fwd1.h" #include "fwd2.h" int main (int argc, char** argv, char** env) { Fwd1 *f1 = (Fwd1*)0; Fwd2 *f2 = (Fwd2*)0; fwd1(f1, f2); fwd2(f1, f2); return 0; } Which I am compiling with the command: gcc fwdMain.c fwd1.c fwd2.c -o fwd -Wall I have tried several ideas to resolve the compile errors, but have only managed to replace the errors with other errors ...How do I resolve the circular dependency issue with the least changes to my code? ...Ideally, as a matter of coding style, I would like to avoid putting the word "struct" all over my code.

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• std::stringstream GCC Abnormal Behavior

  - by FlorianZ

  I have a very interesting problem with compiling a short little program on a Mac (GCC 4.2). The function below would only stream chars or strings into the stringstream, but not anything else (int, double, float, etc.) In fact, the fail flag is set if I attempt to convert for example an int into a string. However, removing the preprocessor flag: _GLIBCXX_DEBUG=1, which is set by default in XCode for the debug mode, will yield the desired results / correct behavior. Here is the simple function I am talking about. value is template variable of type T. Tested for int, double, float (not working), char and strings (working). template < typename T > const std::string Attribute<T>::getValueAsString() const { std::ostringstream stringValue; stringValue << value; return stringValue.str(); } Any ideas what I am doing wrong, why this doesn't work, or what the preprocessor flag does to make this not work anymore? Thanks!

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• Short file names versus long file names in Windows

  - by normski

  I have some code which gets the short name from a file path, using GetShortNameW(), and then later retrieves the long name view GetLongNameA(). The original file is of the form "C:/ProgramData/My Folder/File.ext" However, following conversion to short, then back to long, the filename becomes "C:/Program Files/My Folder/Filename.ext". The short name is of the form "C:/PROGRA~2/MY_FOL~1/FIL~1.EXT" The short name is being incorrectly resolved. The code compiles using VS 2005 on Windows 7 (I cannot upgrade the project to VS2008) Does anybody have any idea why this might be happening? DWORD pathLengthNeeded = ::GetShortPathNameW(aRef->GetFilePath().c_str(), NULL, 0); if(pathLengthNeeded != 0) { WCHAR* shortPath = new WCHAR[pathLengthNeeded]; DWORD newPathNameLength = ::GetShortPathNameW(aRef->GetFilePath().c_str(), shortPath, pathLengthNeeded); if(newPathNameLength != 0) { UI_STRING unicodePath(shortPath); std::string asciiPath = StringFromUserString(unicodePath); pathLengthNeeded = ::GetLongPathNameA(asciiPath.c_str(),NULL, 0); if(pathLengthNeeded != 0) {// convert it back to a long path if possible. For goodness sake can't we use Unicode throughout?F char* longPath = new char[pathLengthNeeded]; DWORD newPathNameLength = ::GetLongPathNameA(asciiPath.c_str(), longPath, pathLengthNeeded); if(newPathNameLength != 0) { std::string longPathString(longPath, newPathNameLength); asciiPath = longPathString; } delete [] longPath; } SetFullPathName(asciiPath); } delete [] shortPath; }

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• Is there a way to find out whether a class is a direct base of another class?

  - by user176168

  Hi I'm wondering whether there is a way to find out whether a class is a direct base of another class i.e. in boost type trait terms a is_direct_base_of function. As far as I can see boost doesn't see to support this kind of functionality which leads me to think that its impossible with the current C++ standard. The reason I want it is to do some validation checking on two macro's that are used for a reflection system to specify that one class is derived from another e.g. header.h: #define BASE A #define DERIVED B class A {}; class B : public A { #include <rtti.h> }; rtti.h: // I want to check that the two macro's are correct with a compile time assert Rtti<BASE, DERIVED> m_rtti; Although the macro's seem unnecessary in this simple example in my real world scenario rtti.h is a lot more complex. One possible avenue would be to compare the size of the this pointer with the size of a this pointer cast to the base type and some how trying to figure out whether its the size of the base class itself away or something (yeah your right I don't know how that would work either! lol)

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• C++: Copy contructor: Use Getters or access member vars directly?

  - by cbrulak

  Have a simple container class: public Container { public: Container() {} Container(const Container& cont) //option 1 { SetMyString(cont.GetMyString()); } //OR Container(const Container& cont) //option 2 { m_str1 = cont.m_str1; } public string GetMyString() { return m_str1;} public void SetMyString(string str) { m_str1 = str;} private: string m_str1; } So, would you recommend this method or accessing the member variables directly? In the example, all code is inline, but in our real code there is no inline code. Update (29 Sept 09): Some of these answers are well written however they seem to get missing the point of this question: this is simple contrived example to discuss using getters/setters vs variables initializer lists or private validator functions are not really part of this question. I'm wondering if either design will make the code easier to maintain and expand. Some ppl are focusing on the string in this example however it is just an example, imagine it is a different object instead. I'm not concerned about performance. we're not programming on the PDP-11

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