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  • Does C# compile code inside an if(false) block?

    - by aximili
    I am just wondering if these code blocks gets compiled into .dll I don't think this one gets compiled at all #if SOMETHING_UNDEFINED // some code - this is ignored by the compiler #endif Now what about these? 1. if(false) { // some code - is this compiled? } 2. const bool F = false; if(F) { // some code - is this compiled? } 3. bool F = false; if(F) { // some code - is this compiled? }

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  • How to log C++ exception if running outside debugger, otherwise rethrow

    - by Stefan Monov
    I wanna do something like this: int main() { try { runApp(); } catch(std::exception const& ex) { if(runningInDebugger()) throw; // let the IDE show me what went wrong else displayMsgBox("Something went wrong! " + ex.what()); } } Needs to work at least in VS2008 but the more debuggers it supports, the better. I want it to check for a debugger at runtime. I don't want to do "#ifdef NDEBUG", because I prefer not to do release builds at all (can't be bothered). So what should I use as a "runningInDebugger()" check?

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  • Template class implicit copy constructor issues

    - by Nate
    Stepping through my program in gdb, line 108 returns right back to the calling function, and doesn't call the copy constructor in class A, like (I thought) it should: template <class S> class A{ //etc... A( const A & old ){ //do stuff... } //etc... }; template <class T> class B{ //etc... A<T> ReturnsAnA(){ A<T> result; // do some stuff with result return result; //line 108 } //etc... }; Any hints? I've banged my head against the wall about this for 4 hours now, and can't seem to come up with what's happening here.

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  • Operator() as a subscript (C++)

    - by Ivan Gromov
    I use operator() as a subscript operator this way: double CVector::operator() (int i) const { if (i >= 0 && i < this->size) return this->data[i]; else return 0; } double& CVector::operator() (int i) { return (this->data[i]); } It works when I get values, but I get an error when I try to write assign a value using a(i) = 1; UPD: Error text: Unhandled exception at 0x651cf54a (msvcr100d.dll) in CG.exe: 0xC0000005: Access violation reading location 0xccccccc0.

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  • Limit scope of #define

    - by Ujjwal Singh
    What is the correct strategy to limit the scope of #define and avoid unwarrented token collisions. In the following configuration: Main.c # include "Utility_1.h" # include "Utility_2.h" VOID Utility() // Was written without knowing of: Utility_1 & Utility_2 { const UINT ZERO = 0; } VOID Main() { ... } // Collision; for Line:5 Compiler does not indicate what replaced Utility_1.h # define ZERO "Zero" # define ONE "One" BOOL Utility_1(); Utility_2.h # define ZERO '0' # define ONE '1' BOOL Utility_2(); Utility_2.c # include "Utility_2.h" BOOL Utility_2() { // Using: ZERO & ONE } //Collision: Character Literal replaced with String {Edit} Note: This is supposed to be a generic quesition so do not limit yourself to enum or other defined types. i.e. What to do when: I MUST USE #define Please comment on my proposed solution below.. _

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  • Transferring data from 2d Dynamic array in C to CUDA and back

    - by Soumya
    I have a dynamically declared 2D array in my C program, the contents of which I want to transfer to a CUDA kernel for further processing. Once processed, I want to populate the dynamically declared 2D array in my C code with the CUDA processed data. I am able to do this with static 2D C arrays but not with dynamically declared C arrays. Any inputs would be welcome! I mean the dynamic array of dynamic arrays. The test code that I have written is as below. #include "cuda_runtime.h" #include "device_launch_parameters.h" #include <stdio.h> #include <conio.h> #include <math.h> #include <stdlib.h> const int nItt = 10; const int nP = 5; __device__ int d_nItt = 10; __device__ int d_nP = 5; __global__ void arr_chk(float *d_x_k, float *d_w_k, int row_num) { int index = (blockIdx.x * blockDim.x) + threadIdx.x; int index1 = (row_num * d_nP) + index; if ( (index1 >= row_num * d_nP) && (index1 < ((row_num +1)*d_nP))) //Modifying only one row data pertaining to one particular iteration { d_x_k[index1] = row_num * d_nP; d_w_k[index1] = index; } } float **mat_create2(int r, int c) { float **dynamicArray; dynamicArray = (float **) malloc (sizeof (float)*r); for(int i=0; i<r; i++) { dynamicArray[i] = (float *) malloc (sizeof (float)*c); for(int j= 0; j<c;j++) { dynamicArray[i][j] = 0; } } return dynamicArray; } /* Freeing memory - here only number of rows are passed*/ void cleanup2d(float **mat_arr, int x) { int i; for(i=0; i<x; i++) { free(mat_arr[i]); } free(mat_arr); } int main() { //float w_k[nItt][nP]; //Static array declaration - works! //float x_k[nItt][nP]; // if I uncomment this dynamic declaration and comment the static one, it does not work..... float **w_k = mat_create2(nItt,nP); float **x_k = mat_create2(nItt,nP); float *d_w_k, *d_x_k; // Device variables for w_k and x_k int nblocks, blocksize, nthreads; for(int i=0;i<nItt;i++) { for(int j=0;j<nP;j++) { x_k[i][j] = (nP*i); w_k[i][j] = j; } } for(int i=0;i<nItt;i++) { for(int j=0;j<nP;j++) { printf("x_k[%d][%d] = %f\t",i,j,x_k[i][j]); printf("w_k[%d][%d] = %f\n",i,j,w_k[i][j]); } } int size1 = nItt * nP * sizeof(float); printf("\nThe array size in memory bytes is: %d\n",size1); cudaMalloc( (void**)&d_x_k, size1 ); cudaMalloc( (void**)&d_w_k, size1 ); if((nP*nItt)<32) { blocksize = nP*nItt; nblocks = 1; } else { blocksize = 32; // Defines the number of threads running per block. Taken equal to warp size nthreads = blocksize; nblocks = ceil(float(nP*nItt) / nthreads); // Calculated total number of blocks thus required } for(int i = 0; i< nItt; i++) { cudaMemcpy( d_x_k, x_k, size1,cudaMemcpyHostToDevice ); //copy of x_k to device cudaMemcpy( d_w_k, w_k, size1,cudaMemcpyHostToDevice ); //copy of w_k to device arr_chk<<<nblocks, blocksize>>>(d_x_k,d_w_k,i); cudaMemcpy( x_k, d_x_k, size1, cudaMemcpyDeviceToHost ); cudaMemcpy( w_k, d_w_k, size1, cudaMemcpyDeviceToHost ); } printf("\nVerification after return from gpu\n"); for(int i = 0; i<nItt; i++) { for(int j=0;j<nP;j++) { printf("x_k[%d][%d] = %f\t",i,j,x_k[i][j]); printf("w_k[%d][%d] = %f\n",i,j,w_k[i][j]); } } cudaFree( d_x_k ); cudaFree( d_w_k ); cleanup2d(x_k,nItt); cleanup2d(w_k,nItt); getch(); return 0;

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  • Access violation reading location 0x00184000.

    - by numerical25
    having troubles with the following line HR(md3dDevice->CreateBuffer(&vbd, &vinitData, &mVB)); it appears the CreateBuffer method is having troubles reading &mVB. mVB is defined in box.h and looks like this ID3D10Buffer* mVB; Below is the code it its entirety. this is all files that mVB is in. //Box.cpp #include "Box.h" #include "Vertex.h" #include <vector> Box::Box() : mNumVertices(0), mNumFaces(0), md3dDevice(0), mVB(0), mIB(0) { } Box::~Box() { ReleaseCOM(mVB); ReleaseCOM(mIB); } float Box::getHeight(float x, float z)const { return 0.3f*(z*sinf(0.1f*x) + x*cosf(0.1f*z)); } void Box::init(ID3D10Device* device, float m, float n, float dx) { md3dDevice = device; mNumVertices = m*n; mNumFaces = 12; float halfWidth = (n-1)*dx*0.5f; float halfDepth = (m-1)*dx*0.5f; std::vector<Vertex> vertices(mNumVertices); for(DWORD i = 0; i < m; ++i) { float z = halfDepth - (i * dx); for(DWORD j = 0; j < n; ++j) { float x = -halfWidth + (j* dx); float y = getHeight(x,z); vertices[i*n+j].pos = D3DXVECTOR3(x, y, z); if(y < -10.0f) vertices[i*n+j].color = BEACH_SAND; else if( y < 5.0f) vertices[i*n+j].color = LIGHT_YELLOW_GREEN; else if (y < 12.0f) vertices[i*n+j].color = DARK_YELLOW_GREEN; else if (y < 20.0f) vertices[i*n+j].color = DARKBROWN; else vertices[i*n+j].color = WHITE; } } D3D10_BUFFER_DESC vbd; vbd.Usage = D3D10_USAGE_IMMUTABLE; vbd.ByteWidth = sizeof(Vertex) * mNumVertices; vbd.BindFlags = D3D10_BIND_VERTEX_BUFFER; vbd.CPUAccessFlags = 0; vbd.MiscFlags = 0; D3D10_SUBRESOURCE_DATA vinitData; vinitData.pSysMem = &vertices; HR(md3dDevice->CreateBuffer(&vbd, &vinitData, &mVB)); //create the index buffer std::vector<DWORD> indices(mNumFaces*3); // 3 indices per face int k = 0; for(DWORD i = 0; i < m-1; ++i) { for(DWORD j = 0; j < n-1; ++j) { indices[k] = i*n+j; indices[k+1] = i*n+j+1; indices[k+2] = (i*1)*n+j; indices[k+3] = (i*1)*n+j; indices[k+4] = i*n+j+1; indices[k+5] = (i*1)*n+j+1; k+= 6; } } D3D10_BUFFER_DESC ibd; ibd.Usage = D3D10_USAGE_IMMUTABLE; ibd.ByteWidth = sizeof(DWORD) * mNumFaces*3; ibd.BindFlags = D3D10_BIND_INDEX_BUFFER; ibd.CPUAccessFlags = 0; ibd.MiscFlags = 0; D3D10_SUBRESOURCE_DATA iinitData; iinitData.pSysMem = &indices; HR(md3dDevice->CreateBuffer(&ibd, &iinitData, &mIB)); } void Box::Draw() { UINT stride = sizeof(Vertex); UINT offset = 0; md3dDevice->IASetVertexBuffers(0, 1, &mVB, &stride, &offset); md3dDevice->IASetIndexBuffer(mIB, DXGI_FORMAT_R32_UINT, 0); md3dDevice->DrawIndexed(mNumFaces*3, 0 , 0); } //Box.h #ifndef _BOX_H #define _BOX_H #include "d3dUtil.h" Box.h class Box { public: Box(); ~Box(); void init(ID3D10Device* device, float m, float n, float dx); void Draw(); float getHeight(float x, float z)const; private: DWORD mNumVertices; DWORD mNumFaces; ID3D10Device* md3dDevice; ID3D10Buffer* mVB; ID3D10Buffer* mIB; }; #endif Thanks again for the help

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  • STL member variable initalization issue with windows API

    - by Django
    I am creating a windows app that uses a vector of stings as a member variable. For some reason, I can compile but when it tries to get at any of the vectors members is crashes. the error is 0xC0000005: Access violation reading location 0xcdcdcdd9. in the member function of the vector class. this is the size() function where it breaks. size_type capacity() const { // return current length of allocated storage return (this->_Myend - this->_Myfirst); } I am using visual studios 2010. thank you Django

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  • Does a static object within a function introduce a potential race condition?

    - by Jeremy Friesner
    I'm curious about the following code: class MyClass { public: MyClass() : _myArray(new int[1024]) {} ~MyClass() {delete [] _myArray;} private: int * _myArray; }; // This function may be called by different threads in an unsynchronized manner void MyFunction() { static const MyClass _myClassObject; [...] } Is there a possible race condition in the above code? Specifically, is the compiler likely to generate code equivalent to the following, "behind the scenes"? void MyFunction() { static bool _myClassObjectInitialized = false; if (_myClassObjectInitialized == false) { _myClassObjectInitialized = true; _myClassObject.MyClass(); // call constructor to set up object } [...] } ... in which case, if two threads were to call MyFunction() nearly-simultaneously, then _myArray might get allocated twice, causing a memory leak? Or is this handled correctly somehow?

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  • Lazy evaluation with ostream C++ operators

    - by SavinG
    I am looking for a portable way to implement lazy evaluation in C++ for logging class. Let's say that I have a simple logging function like void syslog(int priority, const char *format, ...); then in syslog() function we can do: if (priority < current_priority) return; so we never actually call the formatting function (sprintf). On the other hand, if we use logging stream like log << LOG_NOTICE << "test " << 123; all the formating is always executed, which may take a lot of time. Is there any possibility to actually use all the goodies of ostream (like custom << operator for classes, type safety, elegant syntax...) in a way that the formating is executed AFTER the logging level is checked ?

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  • How return a std::string from C's "getcwd" function

    - by rubenvb
    Sorry to keep hammering on this, but I'm trying to learn :). Is this any good? And yes, I care about memory leaks. I can't find a decent way of preallocating the char*, because there simply seems to be no cross-platform way. const string getcwd() { char* a_cwd = getcwd(NULL,0); string s_cwd(a_cwd); free(a_cwd); return s_cwd; } UPDATE2: without Boost or Qt, the most common stuff can get long-winded (see accepted answer)

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  • Accessing Password Protected Network Drives in Windows in C#?

    - by tkeE2036
    Hi Everyone, So in C# I am trying to access a file on a network, for example at "//applications/myapp/test.txt", as follows: const string fileLocation = @"//applications/myapp/test.txt"; using (StreamReader fin = new StreamReader(FileLocation)) { while(!fin.EndOfStream()){ //Do some cool stuff with file } } However I get the following error: System.IO.IOException : Logon failure: unknown user name or bad password. I figure its because I need to supply some network credentials but I'm not sure how to get those to work in this situation. Does anyone know the best way (or any way) to gain access to these files that are on a a password protected location? Thanks in advance!!

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  • strange results with /fp:fast

    - by martinus
    We have some code that looks like this: inline int calc_something(double x) { if (x > 0.0) { // do something return 1; } else { // do something else return 0; } } Unfortunately, when using the flag /fp:fast, we get calc_something(0)==1 so we are clearly taking the wrong code path. This only happens when we use the method at multiple points in our code with different parameters, so I think there is some fishy optimization going on here from the compiler (Microsoft Visual Studio 2008, SP1). Also, the above problem goes away when we change the interface to inline int calc_something(const double& x) { But I have no idea why this fixes the strange behaviour. Can anyone explane this behaviour? If I cannot understand what's going on we will have to remove the /fp:fastswitch, but this would make our application quite a bit slower.

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  • How to change FPU context in signal handler (C++/Linux)

    - by Henry Fané
    I wrote a signal handler to catch FPE errors. I need to continue execution even if this happens. I receive a ucontext_t as parameter, I can change the bad operand from 0 to another value but the FPU context is still bad and I run into an infinite loop ? Does someone already manupulate the ucontext_t structure on Linux ? I finally found a way to handle these situations by clearing the status flag of ucontext_t like this: ... const long int cFPUStatusFlag = 0x3F; aContext->uc_mcontext.fpregs->sw &= ~cFPUStatusFlag; ... 0x3F is negated to put 0 in the 6 bits of the status register of the FPU (x87). Doing this implies to check for FPE exceptions after calculation.

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  • How can I require an attribute on a class definition?

    - by spoulson
    Is there a way to enforce a compile requirement for certain attributes on a class or interface implementation? For example, let's say my application uses a series of static classes that contain const int resource values. I'd like to decorate the class in a Description attribute to describe its contents. In concept, I'd like to apply this attribute requirement to an interface, then each static class would implement it with its required Description. I could write a run-time check or a unit test to check compliance. But really a compile-time check would be best. Is there such a thing?

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  • Creating ostream manipulators for a specific class

    - by petersohn
    I have a class that is derived from ostream: class my_ostream: public std::ostream { // ... } I want to make a manipulator (for example do_something), that works specifically to this class, like this: my_ostream s; s << "some text" << do_something << "some more text"; I did the following: std::ostream &do_something(std::ostream &os) { my_ostream *s = dynamic_cast<my_ostream*>(&os); if (s != NULL) { // do something } return os; } This works, but is rather ugly. I tried the following: my_ostream &do_something(my_ostream &s) { // do something return s; } This doesn't work. I also tried another approach: class my_ostream: public std::ostream { // ... my_ostream &operator<<(const do_something & x) { // do something return *this; } } This still doesn't work.

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  • Check if a SQL table exists.

    - by Carra
    What's the best way to check if a table exists in a Sql database in a database independant way? I came up with: bool exists; const string sqlStatement = @"SELECT COUNT(*) FROM my_table"; try { using (OdbcCommand cmd = new OdbcCommand(sqlStatement, myOdbcConnection)) { cmd.ExecuteScalar(); exists = true; } } catch (Exception ex) { exists = false; } Is there a better way to do this? This method will not work when the connection to the database fails. I've found ways for Sybase, SQL server, Oracle but nothing that works for all databases.

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  • Linq to SQL Strange SQL Translation

    - by Master Morality
    I have a simple query that is generating some odd SQL translations, which is blowing up my code when the object is saturated. from x in DataContext.MyEntities select new { IsTypeCDA = x.EntityType == "CDA" //x.EntityType is a string and EntityType.CDA is a const string... } I would expect this query should translate to: SELECT (CASE WHEN [t0].[EntityType] = @p1 THEN 1 ELSE 0 END) as [IsTypeCDA] ... Instead I get this : SELECT (CASE WHEN @p1 = [t0].[EntityType] THEN 1 WHEN NOT (@p1 = [t0].[EntityType]) THEN 0 ELSE NULL END) AS [IsTypeCDA] ... Since I'm saturating a POCO where IsTypeCDA is a bool, it blows up stating I can't assign null to bool. Any thoughts? Edit: fixed the property names so they make sense...

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  • CryptGenRandom to generate asp.net session id

    - by DoDo
    Hi! does anyone have working example of CryptGenrRandom class to generate session id (need to use in my iis module). HCRYPTPROV hCryptProv; BYTE pbData[16]; if(CryptAcquireContext( &hCryptProv, NULL, NULL, PROV_RSA_FULL, CRYPT_VERIFYCONTEXT)) { if(CryptGenRandom(hCryptProv, 8, pbData)) { std::string s(( const char *) pbData); printf(s.c_str()); } else { MyHandleError("Error during CryptGenRandom."); } } else { MyHandleError("Error during CryptAcquireContext!\n"); } i tried this code but, its not working quite well (i get it from msdn) and this example don't work for me ( http://www.codeproject.com/KB/security/plaintextsessionkey.aspx ) so if anyone know how to generate sessionid using this class plz let me know tnx anyway!

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  • Floating point precision nuances.

    - by user247077
    Hi, I found this code in NVIDIA's cuda SDK samples. void computeGold( float* reference, float* idata, const unsigned int len) { reference[0] = 0; double total_sum = 0; unsigned int i; for( i = 1; i < len; ++i) { total_sum += idata[i-1]; reference[i] = idata[i-1] + reference[i-1]; } // Here it should be okay to use != because we have integer values // in a range where float can be exactly represented if (total_sum != reference[i-1]) printf("Warning: exceeding single-precision accuracy. Scan will be inaccurate.\n"); } (C) Nvidia Corp Can somebody please tell me a case where the warning would be printed, and most importantly, why. Thank you very much.

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  • Need to create a string token dynamically base on which method is calling it

    - by sa
    This is a minimal code. I have the string Str which is used by various methods. I want to in getId method be able to do 2 things Assign class="PDP" to it and Give it a value3 So the final string looks like <tr class='PDP' id='{2}'> <td {0}</td><td>{1}</td></tr> But please note that I will need different values for class in different methods so some Str will have PDP, another will have PTM etc. Is there a clean way to achieve this . private const string Str = "<tr><td >{0}</td><td>{1}</td></tr>"; public static string getId() { string field=string.Format(str, value1,value2, found=true? value3:""); }

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  • How to get this to compile?

    - by ShaChris23
    I have this code which compiles and works as expected: class Right {}; class Left { public: Left& operator = (Right const&) { //... Do something ... return *this; } }; int main() { Right right; Left left; // Assign individual object -- this works left = right; } But now, this one surprises me, I thought the template would work itself out since I already provided the = operator() to the Left class. int main() { ... std::list<Right> rightLst; std::list<Left> leftLst; // Assign a list of objects -- this doesn't compile leftLst = rightLst; } What can I do so that I could convert the rightLst to leftLst conversion in a single line?

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  • How to resolve error "Run-Time Check Failure #3"?

    - by karikari
    I am working on MS Visual Studio. I keep on getting this error: "Run-Time Check Failure #3 - The variable 'test' is being used without being initialized." I don't have any idea how to solve this. Here is the code that I'm currently tries to modify: STDMETHODIMP CButtonDemoBHO::Exec(const GUID*, DWORD nCmdID, DWORD d, VARIANTARG*, VARIANTARG* pvaOut) { CRebarHandler *test; switch (nCmdID){ case BUTTON_PRESSED: MessageBox(m_hWnd, L"You have pressed the button", L"Button Pressed", MB_OK); test->findButton(m_hWnd); test->setmenu(); break; case MENU_ITEM_SELECT: MessageBox(m_hWnd, L"You have simulated a button press with the menu ", L"Menu Pressed", MB_OK); break; } return S_OK; }

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  • How do I use "this" in a member function?

    - by Peter Stewart
    I've written a member function of class Node to read a tree of Nodes in postfix order. It will be called by the Node instance which is the root node of the tree. So: N.postfix(); these appear to be illeagal: *this->left.postfix(); *this->right.postfix(); What is the proper way to do this? class Node { public: const char *cargo; int depth; Node *left; Node *right void Node::postfix() { if (this==__nullptr) { return; } else { *this->left.postfix(); *this->right.postfix(); out<<*this->cargo<<"\n"; return; } };

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