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  • googletest and EXPECT_THROW weirdness

    - by thumper
    I have a class that has no default constructor, but the construct may throw. I was wanting to have a test like: EXPECT_THROW(MyClass(param), std::runtime_error); But the compiler, g++, complains that there is no default constructor for Myclass. However the following: EXPECT_THROW(MyClass foo(param), std::runtime_error); Works, and the test passes as expected. Why though won't googletest accept the temporary object?

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  • A mysterious compilation error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>'

    - by Stephane Rolland
    I wanted to protect the access to a log file that I use for multithreaded logging with boostlog library. I tried this stream class class ThreadSafeStream { public: template <typename TInput> const ThreadSafeStream& operator<< (const TInput &tInput) const { // some thread safe file access return *this; } }; using it this way (text_sink is a boostlog object): //... m_spSink.reset(new text_sink); text_sink::locked_backend_ptr pBackend = m_spSink->locked_backend(); const boost::shared_ptr< ThreadSafeStream >& spFileStream = boost::make_shared<ThreadSafeStream>(); pBackend->add_stream(spFileStream); // this causes the compilation error and I get this mysterious error: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' the whole compile error: Log.cpp(79): error C2664: 'boost::log2_mt_nt5::sinks::basic_text_ostream_backend<CharT>::add_stream' : cannot convert parameter 1 from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T> &' 1> with 1> [ 1> CharT=char 1> ] 1> and 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> Reason: cannot convert from 'const boost::shared_ptr<T>' to 'const boost::shared_ptr<T>' 1> with 1> [ 1> T=ThreadSafeStream 1> ] 1> and 1> [ 1> T=std::basic_ostream<char,std::char_traits<char>> 1> ] 1> No user-defined-conversion operator available that can perform this conversion, or the operator cannot be called I suspect that I am not well defining the operator<<()... but I don't find what is wrong.

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  • Floating point vs integer calculations on modern hardware

    - by maxpenguin
    I am doing some performance critical work in C++, and we are currently using integer calculations for problems that are inherently floating point because "its faster". This causes a whole lot of annoying problems and adds a lot of annoying code. Now, I remember reading about how floating point calculations were so slow approximately circa the 386 days, where I believe (IIRC) that there was an optional co-proccessor. But surely nowadays with exponentially more complex and powerful CPUs it makes no difference in "speed" if doing floating point or integer calculation? Especially since the actual calculation time is tiny compared to something like causing a pipeline stall or fetching something from main memory? I know the correct answer is to benchmark on the target hardware, what would be a good way to test this? I wrote two tiny C++ programs and compared their run time with "time" on Linux, but the actual run time is too variable (doesn't help I am running on a virtual server). Short of spending my entire day running hundreds of benchmarks, making graphs etc. is there something I can do to get a reasonable test of the relative speed? Any ideas or thoughts? Am I completely wrong? The programs I used as follows, they are not identical by any means: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { int accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += rand( ) % 365; } std::cout << accum << std::endl; return 0; } Program 2: #include <iostream> #include <cmath> #include <cstdlib> #include <time.h> int main( int argc, char** argv ) { float accum = 0; srand( time( NULL ) ); for( unsigned int i = 0; i < 100000000; ++i ) { accum += (float)( rand( ) % 365 ); } std::cout << accum << std::endl; return 0; } Thanks in advance!

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  • POD global object initialization

    - by paercebal
    I've got bitten today by a bug. The following source can be copy/pasted (and then compiled) into a main.cpp file #include <iostream> // The point of SomeGlobalObject is for its // constructor to be launched before the main // ... struct SomeGlobalObject { SomeGlobalObject() ; } ; // ... // Which explains the global object SomeGlobalObject oSomeGlobalObject ; // A POD... I was hoping it would be constructed at // compile time when using an argument list struct MyPod { short m_short ; const char * const m_string ; } ; // declaration/Initialization of a MyPod array MyPod myArrayOfPod[] = { { 1, "Hello" }, { 2, "World" }, { 3, " !" } } ; // declaration/Initialization of an array of array of void * void * myArrayOfVoid[][2] = { { (void *)1, "Hello" }, { (void *)2, "World" }, { (void *)3, " !" } } ; // constructor of the global object... Launched BEFORE main SomeGlobalObject::SomeGlobalObject() { std::cout << "myArrayOfPod[0].m_short : " << myArrayOfPod[0].m_short << std::endl ; std::cout << "myArrayOfVoid[0][0] : " << myArrayOfVoid[0][0] << std::endl ; } // main... What else ? int main(int argc, char* argv[]) { return 0 ; } MyPod being a POD, I believed there would be no constructors. Only initialization at compile time. Thus, the global object SomeGlobalObject would have no problem to use the global array of PODs upon its construction. The problem is that in real life, nothing is so simple. On Visual C++ 2008 (I did not test on other compilers), upon execution myArrayOfPodis not initialized, even ifmyArrayOfVoid` is initialized. So my questions is: Are C++ compilers not supposed to initialize global PODs (including POD structures) at compilation time ? Note that I know global variable are evil, and I know that one can't be sure of the order of creation of global variables declared in different compilation units. The problem here is really the POD C-like initialization which seems to call a constructor (the default, compiler-generated one?). And to make everyone happy: This is on debug. On release, the global array of PODs is correctly initialized.

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  • GDI+ crashes when loading PNG from IStream

    - by konforce
    I wrote something to load PNG files from a custom C++ IStream via GDI+. It worked great until I ran it on Vista machines. Crashes every time. When compiled on VS 2008, I found that inserting code into the IStream::AddRef method, such as a cout, made the problem go away. When compiling with VS 2010, it still crashes regardless of that. I stripped the program down to its basics. I copied a FileStream straight from Microsoft's documentation. It can load PNGs when using Bitmap::FromFile. It can load JPEGs, GIFs, and BMPs via FromFile or FromStream. So in short: on Vista, PNG files loaded via Bitmap::FromStream crash. #pragma comment(lib, "gdiplus.lib") #include <iostream> #include <objidl.h> #include <gdiplus.h> class FileStream : public IStream { public: FileStream(HANDLE hFile) { _refcount = 1; _hFile = hFile; } ~FileStream() { if (_hFile != INVALID_HANDLE_VALUE) { ::CloseHandle(_hFile); } } public: HRESULT static OpenFile(LPCWSTR pName, IStream ** ppStream, bool fWrite) { HANDLE hFile = ::CreateFileW(pName, fWrite ? GENERIC_WRITE : GENERIC_READ, FILE_SHARE_READ, NULL, fWrite ? CREATE_ALWAYS : OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL); if (hFile == INVALID_HANDLE_VALUE) return HRESULT_FROM_WIN32(GetLastError()); *ppStream = new FileStream(hFile); if(*ppStream == NULL) CloseHandle(hFile); return S_OK; } virtual HRESULT STDMETHODCALLTYPE QueryInterface(REFIID iid, void ** ppvObject) { if (iid == __uuidof(IUnknown) || iid == __uuidof(IStream) || iid == __uuidof(ISequentialStream)) { *ppvObject = static_cast<IStream*>(this); AddRef(); return S_OK; } else return E_NOINTERFACE; } virtual ULONG STDMETHODCALLTYPE AddRef(void) { return (ULONG)InterlockedIncrement(&_refcount); } virtual ULONG STDMETHODCALLTYPE Release(void) { ULONG res = (ULONG) InterlockedDecrement(&_refcount); if (res == 0) delete this; return res; } // ISequentialStream Interface public: virtual HRESULT STDMETHODCALLTYPE Read(void* pv, ULONG cb, ULONG* pcbRead) { ULONG local_pcbRead; BOOL rc = ReadFile(_hFile, pv, cb, &local_pcbRead, NULL); if (pcbRead) *pcbRead = local_pcbRead; return (rc) ? S_OK : HRESULT_FROM_WIN32(GetLastError()); } virtual HRESULT STDMETHODCALLTYPE Write(void const* pv, ULONG cb, ULONG* pcbWritten) { BOOL rc = WriteFile(_hFile, pv, cb, pcbWritten, NULL); return rc ? S_OK : HRESULT_FROM_WIN32(GetLastError()); } // IStream Interface public: virtual HRESULT STDMETHODCALLTYPE SetSize(ULARGE_INTEGER) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE CopyTo(IStream*, ULARGE_INTEGER, ULARGE_INTEGER*, ULARGE_INTEGER*) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Commit(DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Revert(void) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE LockRegion(ULARGE_INTEGER, ULARGE_INTEGER, DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE UnlockRegion(ULARGE_INTEGER, ULARGE_INTEGER, DWORD) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Clone(IStream **) { return E_NOTIMPL; } virtual HRESULT STDMETHODCALLTYPE Seek(LARGE_INTEGER liDistanceToMove, DWORD dwOrigin, ULARGE_INTEGER* lpNewFilePointer) { DWORD dwMoveMethod; switch(dwOrigin) { case STREAM_SEEK_SET: dwMoveMethod = FILE_BEGIN; break; case STREAM_SEEK_CUR: dwMoveMethod = FILE_CURRENT; break; case STREAM_SEEK_END: dwMoveMethod = FILE_END; break; default: return STG_E_INVALIDFUNCTION; break; } if (SetFilePointerEx(_hFile, liDistanceToMove, (PLARGE_INTEGER) lpNewFilePointer, dwMoveMethod) == 0) return HRESULT_FROM_WIN32(GetLastError()); return S_OK; } virtual HRESULT STDMETHODCALLTYPE Stat(STATSTG* pStatstg, DWORD grfStatFlag) { if (GetFileSizeEx(_hFile, (PLARGE_INTEGER) &pStatstg->cbSize) == 0) return HRESULT_FROM_WIN32(GetLastError()); return S_OK; } private: volatile HANDLE _hFile; volatile LONG _refcount; }; #define USE_STREAM int main() { Gdiplus::GdiplusStartupInput gdiplusStartupInput; ULONG_PTR gdiplusToken; Gdiplus::GdiplusStartup(&gdiplusToken, &gdiplusStartupInput, NULL); Gdiplus::Bitmap *bmp; #ifndef USE_STREAM bmp = Gdiplus::Bitmap::FromFile(L"test.png", false); if (!bmp) { std::cerr << " Unable to open image file." << std::endl; return 1; } #else IStream *s; if (FileStream::OpenFile(L"test.png", &s, false) != S_OK) { std::cerr << "Unable to open image file." << std::endl; return 1; } bmp = Gdiplus::Bitmap::FromStream(s, false); #endif std::cout << "Image is " << bmp->GetWidth() << " by " << bmp->GetHeight() << std::endl; Gdiplus::GdiplusShutdown(gdiplusToken); #ifdef USE_STREAM s->Release(); #endif return 0; } Tracing and debugging, shows that it does make some calls to the IStream class. It crashes inside of lastResult = DllExports::GdipCreateBitmapFromStream(stream, &bitmap); from GdiPlusBitmap.h, which is a static inline wrapper over the flat API. Other than the reference counting, the only IStream methods it calls is stat (for file size), read, and seek. Call stack looks like: ntdll.dll!_DbgBreakPoint@0() + 0x1 bytes ntdll.dll!_RtlpBreakPointHeap@4() + 0x28 bytes ntdll.dll!_RtlpValidateHeapEntry@12() + 0x70a3c bytes ntdll.dll!_RtlDebugFreeHeap@12() + 0x9a bytes ntdll.dll!@RtlpFreeHeap@16() + 0x13cdd bytes ntdll.dll!_RtlFreeHeap@12() + 0x2e49 bytes kernel32.dll!_HeapFree@12() + 0x14 bytes ole32.dll!CRetailMalloc_Free() + 0x1c bytes ole32.dll!_CoTaskMemFree@4() + 0x13 bytes GdiPlus.dll!GpPngDecoder::GetImageInfo() + 0x68 bytes GdiPlus.dll!GpDecodedImage::InternalGetImageInfo() + 0x3c bytes GdiPlus.dll!GpDecodedImage::GetImageInfo() + 0x18 bytes GdiPlus.dll!CopyOnWriteBitmap::CopyOnWriteBitmap() + 0x49 bytes GdiPlus.dll!CopyOnWriteBitmap::Create() + 0x1d bytes GdiPlus.dll!GpBitmap::GpBitmap() + 0x2c bytes I was unable to find anybody else with the same problem, so I assume there's something wrong with my implementation...

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  • convert string to argv in c++

    - by aaronstacy
    I have an std::string containing a command to be executed with execv, what is the best "C++" way to convert it to the "char *argv[]" that is required by the second parameter of execv()? To clarify: std::string cmd = "mycommand arg1 arg2"; char *cmd_argv[]; StrToArgv(cmd, cmd_argv); // how do I write this function? execv(cmd_argv[0], cmd_argv);

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  • How do I retrieve program output in Python?

    - by Geoff
    I'm not a Perl user, but from this question deduced that it's exceedingly easy to retrieve the standard output of a program executed through a Perl script using something akin to: $version = `java -version`; How would I go about getting the same end result in Python? Does the above line retrieve standard error (equivalent to C++ std::cerr) and standard log (std::clog) output as well? If not, how can I retrieve those output streams as well? Thanks, Geoff

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  • Error at lapack cgesv when matrix is not singular

    - by Jan Malec
    This is my first post. I usually ask classmates for help, but they have a lot of work now and I'm too desperate to figure this out on my own :). I am working on a project for school and I have come to a point where I need to solve a system of linear equations with complex numbers. I have decided to call lapack routine "cgesv" from c++. I use the c++ complex library to work with complex numbers. Problem is, when I call the routine, I get error code "2". From lapack documentation: INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, U(i,i) is exactly zero. The factorization has been completed, but the factor U is exactly singular, so the solution could not be computed. Therefore, the element U(2, 2) should be zero, but it is not. This is how I declare the function: void cgesv_( int* N, int* NRHS, std::complex* A, int* lda, int* ipiv, std::complex* B, int* ldb, int* INFO ); This is how I use it: int *IPIV = new int[NA]; int INFO, NRHS = 1; std::complex<double> *aMatrix = new std::complex<double>[NA*NA]; for(int i=0; i<NA; i++){ for(int j=0; j<NA; j++){ aMatrix[j*NA+i] = A[i][j]; } } cgesv_( &NA, &NRHS, aMatrix, &NA, IPIV, B, &NB, &INFO ); And this is how the matrix looks like: (1,-160.85) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-40.213) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-0.000613592) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-40.213) (0,0.000306796) (0,-0) (0,-0) (0,-0) (0,0.000306796) (1,-160.85) I had to split the matrix colums, otherwise it did not format correctly. My first suspicion was that complex is not parsed correctly, but I have used lapack functions with complex numbers before this way. Any ideas?

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  • Function-Local Static Const variable Initialization semantics.

    - by Hassan Syed
    The questions are in bold, for those that cannot be bothered reading a question in depth. This is a followup to this question. It is to do with the initialization semantics of static variables in functions. Static variables should be initialized once, and their internal state might be altered later - as I (currently) do in the linked question. However, the code in question does not require the feature to change the state of the variable later. Let me clarrify my position, since I don't require the string object's internal state to change. The code is for a trait class for meta programming, and as such would would benifit from a const char * const ptr -- thus Ideally a local cost static const variable is needed. My educated guess is that in this case the string in question will be optimally placed in memory by the link-loader, and that the code is more secure and maps to the intended semantics. This leads to the semantics of such a variable "The C++ Programming language Third Edition -- Stroustrup" does not have anything (that I could find) to say about this matter. All that is said is that the variable is initialized once when the flow of control of the thread first reaches the code. This leads me to ponder if the following code would be sensible, and if not what are the intended semantics ?. #include <iostream> const char * const GetString(const char * x_in) { static const char * const x = x_in; return x; } int main() { const char * const temp = GetString("yahoo"); std::cout << temp << std::endl; const char * const temp2 = GetString("yahoo2"); std::cout << temp2 << std::endl; } The following compiles on GCC and prints "yahoo" twice. Which is what I want -- However it might not be standards compliant (which is why I post this question). It might be more elegant to have two functions, "SetString" and "String" where the latter forwards to the first. If it is standards compliant does someone know of a templates implementation in boost (or elsewhere) ?

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  • overloading friend operator<< for template class

    - by starcorn
    Hello, I have read couple of the question regarding my problem on stackoverflow now, and none of it seems to solve my problem. Or I maybe have done it wrong... The overloaded << if I make it into an inline function. But how do I make it work in my case? warning: friend declaration std::ostream& operator<<(std::ostream&, const D<classT>&)' declares a non-template function warning: (if this is not what you intended, make sure the function template has already been declared and add <> after the function name here) -Wno-non-template-friend disables this warning /tmp/cc6VTWdv.o:uppgift4.cc:(.text+0x180): undefined reference to operator<<(std::basic_ostream<char, std::char_traits<char> >&, D<int> const&)' collect2: ld returned 1 exit status template <class T> T my_max(T a, T b) { if(a > b) return a; else return b; } template <class classT> class D { public: D(classT in) : d(in) {}; bool operator>(const D& rhs) const; classT operator=(const D<classT>& rhs); friend ostream& operator<< (ostream & os, const D<classT>& rhs); private: classT d; }; int main() { int i1 = 1; int i2 = 2; D<int> d1(i1); D<int> d2(i2); cout << my_max(d1,d2) << endl; return 0; } template <class classT> ostream& operator<<(ostream &os, const D<classT>& rhs) { os << rhs.d; return os; }

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  • Using time facets on universal_time

    - by scooterman
    Hi all, on boost, to create a time facet to format an specified time we use the folowing: boost::local_time::local_time_facet* facet = new boost::local_time::local_time_facet("%Y%m%d %H:%M:%S.%f"); std::stringstream date_stream; date_stream.imbue(std::locale(date_stream.getloc(), facet)); date_stream << boost::local_time::local_microsec_clock::local_time(boost::local_time::time_zone_ptr()); How do I do the same thing, but using an universal clock: boost::posix_time::microsec_clock::universal_time() Thanks

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  • What free tools or strategies can help debug a multi-threading corruption bug?

    - by WilliamKF
    I have a client server application with multi-threading. The server side is failing with a std::list getting corrupted resulting in a SEGV. I suspect that there is some kind of cross thread timing issue going on where the two threads are updating the std::list at the same time and causing it to be corrupted. Please suggest free tools to track this down or strategies that might be helpful.

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  • What is the best way to store incremental downloaded data?

    - by afriza
    Inspired by Chromium's sha1 class, I am thinking to store incrementally downloaded data using std::string // pseudo-code char buff[BUFF_SIZE]; std::string data; do { size = ReadInternetFileTo(buff,BUFF_SIZE); data.append(buff,size); } while (not_finished); Any foreseeable problems with this method or better way to do it?

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  • Any tips on reducing wxWidgets application code size?

    - by Billy ONeal
    I have written a minimal wxWidgets application: stdafx.h #define wxNO_REGEX_LIB #define wxNO_XML_LIB #define wxNO_NET_LIB #define wxNO_EXPAT_LIB #define wxNO_JPEG_LIB #define wxNO_PNG_LIB #define wxNO_TIFF_LIB #define wxNO_ZLIB_LIB #define wxNO_ADV_LIB #define wxNO_HTML_LIB #define wxNO_GL_LIB #define wxNO_QA_LIB #define wxNO_XRC_LIB #define wxNO_AUI_LIB #define wxNO_PROPGRID_LIB #define wxNO_RIBBON_LIB #define wxNO_RICHTEXT_LIB #define wxNO_MEDIA_LIB #define wxNO_STC_LIB #include <wx/wxprec.h> Minimal.cpp #include "stdafx.h" #include <memory> #include <wx/wx.h> class Minimal : public wxApp { public: virtual bool OnInit(); }; IMPLEMENT_APP(Minimal) DECLARE_APP(Minimal) class MinimalFrame : public wxFrame { DECLARE_EVENT_TABLE() public: MinimalFrame(const wxString& title); void OnQuit(wxCommandEvent& e); void OnAbout(wxCommandEvent& e); }; BEGIN_EVENT_TABLE(MinimalFrame, wxFrame) EVT_MENU(wxID_ABOUT, MinimalFrame::OnAbout) EVT_MENU(wxID_EXIT, MinimalFrame::OnQuit) END_EVENT_TABLE() MinimalFrame::MinimalFrame(const wxString& title) : wxFrame(0, wxID_ANY, title) { std::auto_ptr<wxMenu> fileMenu(new wxMenu); fileMenu->Append(wxID_EXIT, L"E&xit\tAlt-X", L"Terminate the Minimal Example."); std::auto_ptr<wxMenu> helpMenu(new wxMenu); helpMenu->Append(wxID_ABOUT, L"&About\tF1", L"Show the about dialog box."); std::auto_ptr<wxMenuBar> bar(new wxMenuBar); bar->Append(fileMenu.get(), L"&File"); fileMenu.release(); bar->Append(helpMenu.get(), L"&Help"); helpMenu.release(); SetMenuBar(bar.get()); bar.release(); CreateStatusBar(2); SetStatusText(L"Welcome to wxWidgets!"); } void MinimalFrame::OnAbout(wxCommandEvent& e) { wxMessageBox(L"Some text about me!", L"About", wxOK, this); } void MinimalFrame::OnQuit(wxCommandEvent& e) { Close(); } bool Minimal::OnInit() { std::auto_ptr<MinimalFrame> mainFrame( new MinimalFrame(L"Minimal wxWidgets Application")); mainFrame->Show(); mainFrame.release(); return true; } This minimal program weighs in at 2.4MB! (Executable compression drops this to half a MB or so but that's still HUGE!) (I must statically link because this application needs to be single-binary-xcopy-deployed, so both the C runtime and wxWidgets itself are set for static linking) Any tips on cutting this down? (I'm using Microsoft Visual Studio 2010)

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  • C++ forward declaration problem

    - by Thomas
    Hi, I have a header file that has some forward declarations but when I include the header file in the implementation file it gets included after the includes for the previous forward declarations and this results in an error like this. error: using typedef-name ‘std::ifstream’ after ‘class’ /usr/include/c++/4.2.1/iosfwd:145: error: ‘std::ifstream’ has a previous declaration. Whats the norm for working around this? Thanks in advance.

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  • C++ Virtual Constructor, without clone()

    - by Julien L.
    I want to perform "deep copies" of an STL container of pointers to polymorphic classes. I know about the Prototype design pattern, implemented by means of the Virtual Ctor Idiom, as explained in the C++ FAQ Lite, Item 20.8. It is simple and straightforward: struct ABC // Abstract Base Class { virtual ~ABC() {} virtual ABC * clone() = 0; }; struct D1 : public ABC { virtual D1 * clone() { return new D1( *this ); } // Covariant Return Type }; A deep copy is then: for( i = 0; i < oldVector.size(); ++i ) newVector.push_back( oldVector[i]->clone() ); Drawbacks As Andrei Alexandrescu states it: The clone() implementation must follow the same pattern in all derived classes; in spite of its repetitive structure, there is no reasonable way to automate defining the clone() member function (beyond macros, that is). Moreover, clients of ABC can possibly do something bad. (I mean, nothing prevents clients to do something bad, so, it will happen.) Better design? My question is: is there another way to make an abstract base class clonable without requiring derived classes to write clone-related code? (Helper class? Templates?) Following is my context. Hopefully, it will help understanding my question. I am designing a class hierarchy to perform operations on a class Image: struct ImgOp { virtual ~ImgOp() {} bool run( Image & ) = 0; }; Image operations are user-defined: clients of the class hierarchy will implement their own classes derived from ImgOp: struct CheckImageSize : public ImgOp { std::size_t w, h; bool run( Image &i ) { return w==i.width() && h==i.height(); } }; struct CheckImageResolution; struct RotateImage; ... Multiple operations can be performed sequentially on an image: bool do_operations( std::vector< ImgOp* > v, Image &i ) { std::for_each( v.begin(), v.end(), /* bind2nd(mem_fun(&ImgOp::run), i ...) don't remember syntax */ ); } int main( ... ) { std::vector< ImgOp* > v; v.push_back( new CheckImageSize ); v.push_back( new CheckImageResolution ); v.push_back( new RotateImage ); Image i; do_operations( v, i ); } If there are multiple images, the set can be split and shared over several threads. To ensure "thread-safety", each thread must have its own copy of all operation objects contained in v -- v becomes a prototype to be deep copied in each thread.

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  • assign member based on string value

    - by Aperion
    I need start off with code because I am not sure what terminology to use. Lets say I have the following code: class Node { public: void Parse(rapidxml::xml_node<> *node) { for (rapidxml::xml_attribute<> *attr = node->first_attribute(); attr; attr = attr->next_attribute()) { std::stringstream converter; converter << attr->value(); if( !strcmp(attr->name(), "x") ) converter >> x; else if( !strcmp(attr->name(),"y") ) converter >> y; else if( !strcmp(attr->name(), "z") ) converter >> z; } } private: float x; float y; float z; }; What I can't stand is the repetition of if( !strcmp(attr-name(), "x") ) converter x; I feel that this is error prone and monotonous, but I cannot think of another way to map a string value to a member assignment. What are some other approaches one can take to avoid code such as this? The only other possible alternative I could think of was to use a hashmap, but that runs into problems with callbacks This is the best I could up with but it's not as flexible as I'd like: class Node { Node() : x(0.0f), y(0.0f), z(0.0f) { assignmentMap["x"] = &x; assignmentMap["y"] = &y; assignmentMap["z"] = &z; } public: void Parse(rapidxml::xml_node<> *node) { for (rapidxml::xml_attribute<> *attr = node->first_attribute(); attr; attr = attr->next_attribute()) { if( !attr->name() ) continue; std::stringstream converter; converter << attr->value(); converter >> *assignmentMap[attr->name()]; } } private: float x; float y; float z; std::map<std::string, float*> assignmentMap; };

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  • C++ Deck and Card Class Error with bad alloc

    - by user3702164
    Just started learn to code in school. Our assignment requires us to create a card game with card,deck and hand class. I am having troubles with it now and i keep getting exception: std::bad_alloc at memory location. Here are my codes right now CardType h: #ifndef cardType_h #define cardType_h #include <string> using namespace std; class cardType{ public: void print(); int getValue() const; string getSymbol() const; string getSpecial() const; string getSuit() const; int checkSpecial(int gscore) const; cardType(); cardType(string suit,int value); private: int value; string special; string symbol; string suit; }; #endif CardType cpp: #include "cardType.h" #include <iostream> #include <string> using namespace std; void cardType::print() { cout << getSymbol() << " of " << getSuit() << ", having the value of " << getValue() << "."<< endl <<"This card's special is " << getSpecial() << endl; } int cardType::getValue() const { return value; } string cardType::getSymbol() const { return symbol; } string cardType::getSpecial() const { return special; } string cardType::getSuit() const { return suit; } cardType::cardType(){ value=0; symbol="?"; special='?'; suit='?'; } cardType::cardType(string s, int v){ suit = s; value = v; switch(v){ case 1: // Ace cards have a value of 1 and have no special type symbol="Ace"; special="None"; break; case 2: // 2 cards have a value of 2 and have no special type symbol="2"; special="None"; break; case 3: symbol="3"; // 3 cards have a value of 3 and have no special type special="None"; break; case 4: symbol="4"; // 4 cards have a value of 0 and have a special type "Reverse" which reverses the flow of the game special="Reverse"; value=0; break; case 5: symbol="5"; // 5 cards have a value of 5 and have no special type special="None"; break; case 6: symbol="6"; // 6 cards have a value of 6 and have no special type special="None"; break; case 7: symbol="7"; // 7 cards have a value of 7 and have no special type special="None"; break; case 8: symbol="8"; // 8 cards have a value of 8 and have no special type special="None"; break; case 9: symbol="9"; // 9 cards have a value of 0 and have a special type "Pass" which does not add any value to the game and lets the player skip his turn. special="Pass"; value=0; break; case 10: symbol="10"; // 10 cards have a value of 10 and have a special type "subtract" which instead of adding the 10 value to the total game it is subtracted instead. special="Subtract"; value=10; break; case 11: // Jack cards have a value of 10 and have no special type symbol="Jack"; special="None"; value=10; break; case 12: // Queens cards have a value of 10 and have no special type symbol="Queen"; special="None"; value=10; break; case 13: symbol="King"; // King cards have a value of 0 and have a special type "NinetyNine" which changes the total game score to 99 reguardless what number it was previously special="NinetyNine"; value=0; break; } } int cardType::checkSpecial(int gscore) const{ if(special=="Pass"){ return gscore; } if(special=="Reverse"){ return gscore; } if(special=="Subtract"){ return gscore - value; } if(special=="NinetyNine"){ return 99; } else{ return gscore + value; } } DeckType h: #ifndef deckType_h #define deckType_h #include "cardType.h" #include <string> using namespace std; class deckType { public: void shuffle(); cardType dealCard(); deckType(); private: cardType *deck; int current; }; #endif DeckType cpp: #include <iostream> #include "deckType.h" using namespace std; deckType::deckType() { int index = 0; int current=0; deck = new cardType[52]; string suit[] = {"Hearts","Diamonds","Clubs","Spades"}; int value[] = {1,2,3,4,5,6,7,8,9,10,11,12,13}; for ( int i = 0; i <= 3; i++ ) { for ( int j = 1; j <= 13; j++ ) { deck[index] = cardType(suit[i],value[j]); index++; } } } cardType deckType::dealCard() { return deck[current]; current++; } Main cpp : #include "deckType.h" #include <iostream> using namespace std; int main() { deckType gamedeck; cout << "1" <<endl; cardType currentCard; cout << "2" <<endl; currentCard = gamedeck.dealCard(); cout << "3" <<endl; return 0; } I keep getting bad_alloc at the currentCard = gamedeck.dealCard(); I really do not know what i have done wrong.

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  • GCC problem with raw double type comparisons

    - by Monomer
    I have the following bit of code, however when compiling it with GCC 4.4 with various optimization flags I get some unexpected results when its run. #include <iostream> int main() { const unsigned int cnt = 10; double lst[cnt] = { 0.0 }; const double v[4] = { 131.313, 737.373, 979.797, 731.137 }; for(unsigned int i = 0; i < cnt; ++i) { lst[i] = v[i % 4] * i; } for(unsigned int i = 0; i < cnt; ++i) { double d = v[i % 4] * i; if(lst[i] != d) { std::cout << "error @ : " << i << std::endl; return 1; } } return 0; } when compiled with: "g++ -pedantic -Wall -Werror -O1 -o test test.cpp" I get the following output: "error @ : 3" when compiled with: "g++ -pedantic -Wall -Werror -O2 -o test test.cpp" I get the following output: "error @ : 3" when compiled with: "g++ -pedantic -Wall -Werror -O3 -o test test.cpp" I get no errors when compiled with: "g++ -pedantic -Wall -Werror -o test test.cpp" I get no errors I do not believe this to be an issue related to rounding, or epsilon difference in the comparison. I've tried this with Intel v10 and MSVC 9.0 and they all seem to work as expected. I believe this should be nothing more than a bitwise compare. If I replace the if-statement with the following: if (static_cast<long long int>(lst[i]) != static_cast<long long int>(d)), and add "-Wno-long-long" I get no errors in any of the optimization modes when run. If I add std::cout << d << std::endl; before the "return 1", I get no errors in any of the optimization modes when run. Is this a bug in my code, or is there something wrong with GCC and the way it handles the double type?

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  • Translating C++'s sprintf format string to C#'s string.Format

    - by thebackup
    I found the following C++ code (comments added myself): // frame_name is a char array // prefix is std::string // k is a for loop counter // frames is a std::vector string sprintf(frameName, "%s_%0*s.bmp", prefix.c_str(), k, frames[k].c_str()); I then try to translate it to C# // prefix is string // k is a for loop counter // frames is List<string> string frameName = string.Format("{0}_(what goes in here?).bmp", prefix, k, frames[k]); Basically, what would be the C# equivalent of the C++ format string "%s_%0*s.bmp"?

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