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  • Embedding Python and adding C functions to the interpreter

    - by monoceres
    I'm currently writing an applications that embedds the python interpreter. The idea is to have the program call user specified scripts on certain events in the program. I managed this part but now I want the scripts to be able to call functions in my program. Here's my code so far: #include "python.h" static PyObject* myTest(PyObject* self,PyObject *args) { return Py_BuildValue("s","123456789"); } static PyMethodDef myMethods[] = {{"myTest",myTest},{NULL,NULL}}; int main() { Py_Initialize(); Py_InitModule("PROGRAM",myMethods); PyRun_SimpleString("print PROGRAM.myTest()"); Py_Finalize(); } Thanks!

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  • Passing a template func. as a func. ptr to an overloaded func. - is there a way to compile this code

    - by LoudNPossiblyRight
    Just a general c++ curiosity: This code below shouldn't compile because it's impossible to know which to instantiate: temp(const int&) or temp(const string&) when calling func(temp) - this part i know. What i would like to know is if there is anything i can do to the line marked PASSINGLINE to get the compiler to deduce that i want FPTR1 called and not FPTR2 ? #include<iostream> using std::cout; using std::endl; /*FPTR1*/ void func(void(*fptr)(const int&)){ fptr(1001001);} /*FPTR2*/ void func(void(*fptr)(const string&)){ fptr("1001001"); } template <typename T> void temp(const T &t){ cout << t << endl; } int main(){ /*PASSINGLINE*/ func(temp); return 0; } Thank you.

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  • Dangling pointer

    - by viswanathan
    How can the below code result in a dangling pointer. { char *cPointer = malloc ( some constant number ); /* some code */ free ( cPointer ); cPointer = NULL; /* some code */ }

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  • Callback function and function pointer trouble in C++ for a BST

    - by Brendon C.
    I have to create a binary search tree which is templated and can deal with any data types, including abstract data types like objects. Since it is unknown what types of data an object might have and which data is going to be compared, the client side must create a comparison function and also a print function (because also not sure which data has to be printed). I have edited some C code which I was directed to and tried to template, but I cannot figure out how to configure the client display function. I suspect variable 'tree_node' of class BinarySearchTree has to be passed in, but I am not sure how to do this. For this program I'm creating an integer binary search tree and reading data from a file. Any help on the code or the problem would be greatly appreciated :) Main.cpp #include "BinarySearchTreeTemplated.h" #include <iostream> #include <fstream> #include <string> using namespace std; /*Comparison function*/ int cmp_fn(void *data1, void *data2) { if (*((int*)data1) > *((int*)data2)) return 1; else if (*((int*)data1) < *((int*)data2)) return -1; else return 0; } static void displayNode() //<--------NEED HELP HERE { if (node) cout << " " << *((int)node->data) } int main() { ifstream infile("rinput.txt"); BinarySearchTree<int> tree; while (true) { int tmp1; infile >> tmp1; if (infile.eof()) break; tree.insertRoot(tmp1); } return 0; } BinarySearchTree.h (a bit too big to format here) http://pastebin.com/4kSVrPhm

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  • How to determine the end of an integer array when manipulating with integer pointer?

    - by AKN
    Here is the code: int myInt[] ={ 1, 2, 3, 4, 5 }; int *myIntPtr = &myInt[0]; while( *myIntPtr != NULL ) { cout<<*myIntPtr<<endl; myIntPtr++; } Output: 12345....<junks>.......... For Character array: (Since we have a NULL character at the end, no problem while iterating) char myChar[] ={ 'A', 'B', 'C', 'D', 'E', '\0' }; char *myCharPtr = &myChar[0]; while( *myCharPtr != NULL ) { cout<<*myCharPtr<<endl; myCharPtr++; } Output: ABCDE My question is since we say to add NULL character as end of the strings, we rule out such issues! If in case, it is rule to add 0 to the end of integer array, we could have avoided this problem. What say?

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  • Double indirection and structures passed into a function

    - by ZPS
    I am curious why this code works: typedef struct test_struct { int id; } test_struct; void test_func(test_struct ** my_struct) { test_struct my_test_struct; my_test_struct.id=267; *my_struct = &my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); } This works, but pointing to the memory address of a functions local variable is a big no-no, right? But if i used a structure pointer and malloc, that would be the correct way, right? void test_func(test_struct ** my_struct) { test_struct *my_test_struct; my_test_struct = malloc(sizeof(test_struct)); my_test_struct->id=267; *my_struct = my_test_struct; } int main () { test_struct * main_struct; test_func(&main_struct); printf("%d\n",main_struct->id); }

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  • Objective C LValue required as unary '&' operand

    - by Bob
    Hello! In my code, I get this error when I try to get a pointer to my class property. (I wrote a small *.OBJ file translator in Python, discarding the normals) CODE: //line: line of text const char *str = [line UTF8String]; Point3D *p1, *p2, *p3; p1 = [Point3D makeX:0 Y:0 Z:0]; p2 = [Point3D makeX:0 Y:0 Z:0]; p3 = [Point3D makeX:0 Y:0 Z:0]; sscanf(str, "t %f,%f,%f %f,%f,%f %f,%f,%f",(&[p1 x]),&([p1 y]),&([p1 z]),&([p2 x]),&([p2 y]),&([p2 z]),&([p3 x]),&([p3 y]),&([p3 z])); Triangle3D *tri = [Triangle3D make:p1 p2:p2 p3:p3];

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  • C++: Reference and Pointer question (example regarding OpenGL)

    - by Jay
    I would like to load textures, and then have them be used by multiple objects. Would this work? class Sprite { GLuint* mTextures; // do I need this to also be a reference? Sprite( GLuint* textures ) // do I need this to also be a reference? { mTextures = textures; } void Draw( textureNumber ) { glBindTexture( GL_TEXTURE_2D, mTextures[ textureNumber ] ); // drawing code } }; // normally these variables would be inputed, but I did this for simplicity. const int NUMBER_OF_TEXTURES = 40; const int WHICH_TEXTURE = 10; void main() { std::vector<GLuint> the_textures; the_textures.resize( NUMBER_OF_TEXTURES ); glGenTextures( NUMBER_OF_TEXTURES, &the_textures[0] ); // texture loading code Sprite the_sprite( &the_textures[0] ); the_sprite.Draw( WHICH_TEXTURE ); } And is there a different way I should do this, even if it would work? Thanks.

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  • Setting the first two bytes of a block of memory

    - by idealistikz
    Suppose I have a block of memory as such: void *block = malloc(sizeof(void *) + size); How do I set the first two bytes of the block as NULL or have it point somewhere? I do not want to simply assign 'block' to NULL or to another pointer because I want to access the rest of the memory I malloc'ed.

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  • c++/cli pass (managed) delegate to unmanaged code

    - by Ron Klein
    How do I pass a function pointer from managed C++ (C++/CLI) to an unmanaged method? I read a few articles, like this one from MSDN, but it describes two different assemblies, while I want only one. Here is my code: 1) Header (MyInterop.ManagedCppLib.h): #pragma once using namespace System; namespace MyInterop { namespace ManagedCppLib { public ref class MyManagedClass { public: void DoSomething(); }; }} 2) CPP Code (MyInterop.ManagedCppLib.cpp) #include "stdafx.h" #include "MyInterop.ManagedCppLib.h" #pragma unmanaged void UnmanagedMethod(int a, int b, void (*sum)(const int)) { int result = a + b; sum(result); } #pragma managed void MyInterop::ManagedCppLib::MyManagedClass::DoSomething() { System::Console::WriteLine("hello from managed C++"); UnmanagedMethod(3, 7, /* ANY IDEA??? */); } I tried creating my managed delegate and then I tried to use Marshal::GetFunctionPointerForDelegate method, but I couldn't compile.

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  • Why would I get a bus error or segmentation fault when calling free() normally?

    - by chucknelson
    I have a very simple test program, running on Solaris 5.8: #include <stdio.h> #include <stdlib.h> int main(void) { char *paths; paths = getenv("PATH"); printf("Paths: %s\n", paths); free(paths); // this causes a bus error return 0; } If I don't call free() at the end, it displays the message fine and exits. If I include the free() call, it crashes with a bus error. I've had other calls to free(), in other programs, cause segmentation faults as well. Even if I allocate the memory for *paths myself, free() will cause a bus error. Is there some reason trying to free up the memory is causing a crash?

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  • Avoid incompatible pointer warning when dealing with double-indirection

    - by fnawothnig
    Assuming this program: #include <stdio.h> #include <string.h> static void ring_pool_alloc(void **p, size_t n) { static unsigned char pool[256], i = 0; *p = &pool[i]; i += n; } int main(void) { char *str; ring_pool_alloc(&str, 7); strcpy(str, "foobar"); printf("%s\n", str); return 0; } ... is it possible to somehow avoid the GCC warning test.c:12: warning: passing argument 1 of ‘ring_pool_alloc’ from incompatible pointer type test.c:4: note: expected ‘void **’ but argument is of type ‘char **’ ... without casting to (void**) (or simply disabling the compatibility checks)? Because I would very much like to keep compatibility warnings regarding indirection-level...

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  • pointer to a structure in a nested structure

    - by dpka6
    I have a 6 levels of nested structures. I am having problem with last three levels. The program compiles fine but when I run it crashes with Segmentation fault. There is some problem in assignment is what I feel. Kindly point out the error. typedef struct { char addr[6]; int32_t rs; uint16_t ch; uint8_t ap; } C; typedef struct { C *ap_info; } B; typedef struct { union { B wi; } u; } A; function1(char addr , int32_t rs, uint16_t ch, uint8_t ap){ A la; la.u.wi.ap_info->addr[6] = addr; la.u.wi.ap_info->rs = rs; la.u.wi.ap_info->ch = ch; la.u.wi.ap_info->ap = ap; }

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  • C++ arrays as parameters, subscript vs. pointer

    - by awshepard
    Alright, I'm guessing this is an easy question, so I'll take the knocks, but I'm not finding what I need on google or SO. I'd like to create an array in one place, and populate it inside a different function. I define a function: void someFunction(double results[]) { for (int i = 0; i<100; ++i) { for (int n = 0; n<16; ++n) //note this iteration limit { results[n] += i * n; } } } That's an approximation to what my code is doing, but regardless, shouldn't be running into any overflow or out of bounds issues or anything. I generate an array: double result[16]; for(int i = 0; i<16; i++) { result[i] = -1; } then I want to pass it to someFunction someFunction(result); When I set breakpoints and step through the code, upon entering someFunction, results is set to the same address as result, and the value there is -1.000000 as expected. However, when I start iterating through the loop, results[n] doesn't seem to resolve to *(results+n) or *(results+n*sizeof(double)), it just seems to resolve to *(results). What I end up with is that instead of populating my result array, I just get one value. What am I doing wrong?

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  • When should an array name be treated as a pointer and when does it just represent the array itself? [duplicate]

    - by user1087373
    This question already has an answer here: When is an array name or a function name 'converted' into a pointer ? (in C) 4 answers I just made a test program after reading the book and the result turned out confusing: #include <stdio.h> int main(void) { char text[] = "hello!"; printf("sizeof(text):%d sizeof(text+2):%d sizeof(text[0]):%d \n",(int)sizeof(text), sizeof(text+2), sizeof(text[0])); printf("text:%p sizeof(text):%d &text:%p sizeof(&text):%d \n",text, sizeof(text), &text, sizeof(&text)); printf("text+1:%p &text+1:%p \n", text+1, &text+1); return 0; } The result: sizeof(text):7 sizeof(text+2):4 sizeof(text[0]):1 text:0xbfc8769d sizeof(text):7 &text:0xbfc8769d sizeof(&text):4 text+1:0xbfc8769e &text+1:0xbfc876a4 What makes me feel confused are: why the value of 'sizeof(text)' is 7 whereas 'sizeof(text+2)' is 4 what's the difference between 'text' and '&text'?

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  • Passing array to function with pointer loses array size information!

    - by Narek
    If I write int main() { int a[100] = {1,2,3,4,}; cout<<sizeof(a)/sizeof(a[0])<<endl; return 0; } I get 400! If I write void func(int *a); int main() { int a[100] = {1,2,3,4,}; func(a); return 0; } void func(int *a) { cout<<sizeof(a)/sizeof(a[0])<<endl; } Then I get 400! So why passing array to function with pointer loses array size information?

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  • Why does this C++ code result in a segmentation fault?

    - by user69514
    I keep getting a segmentation fault when the readAuthor() method is called. Does anybody know why this happens? I am supposed to use dynamic arrays, I know this would be so easy if I was using static array. #include <iostream> #include <string> #include <cstring> #include <cstdlib> using namespace std; /** declare arrays **/ int* isbnArr = new int[25]; char* authorArr = new char[25]; char* publisherArr = new char[25]; char* titleArr = new char[25]; int* editionArr = new int[25]; int* yearArr = new int[25]; int* pagesArr = new int[25]; float* retailPriceArr = new float[25]; float* discountedPriceArr = new float[25]; int* stockArr = new int[25]; /** function prototypes **/ int readIsbn(); char* readAuthor(); char* readPublisher(); char* readTitle(); int readEdition(); int readYear(); int readPages(); float readMsrp(); float readDiscountedPrice(); int readStockAmount(); void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory); int main() { bool stop = false; //flag when to stop loop int ind = 0; //index for current book while( !stop ){ cout << "Add book: press A: "; cout << "another thing here "; char choice; cin >> choice; if( choice == 'a' || choice == 'A' ){ readonebook(&isbnArr[ind], &authorArr[ind], &titleArr[ind], &publisherArr[ind], &editionArr[ind], &yearArr[ind], &pagesArr[ind], &retailPriceArr[ind], &discountedPriceArr[ind], &stockArr[ind]); test(&authorArr[ind]); ind++; } } return 0; } /** define functions **/ int readIsbn(){ int isbn; cout << "ISBN: "; cin >> isbn; return isbn; } char* readAuthor(){ char* author; cout << "Author: "; cin >> author; return author; } char* readPublisher(){ char* publisher = NULL; cout << "Publisher: "; cin >> publisher; return publisher; } char* readTitle(){ char* title = NULL; cout << "Title: "; cin >> title; return title; } int readEdition(){ int edition; cout << "Edition: "; cin >> edition; return edition; } int readYear(){ int year; cout << "Year: "; cin >> year; return year; } int readPages(){ int pages; cout << "Pages: "; cin >> pages; return pages; } float readMsrp(){ float price; cout << "Retail Price: "; cin >> price; return price; } float readDiscountedPrice(){ float price; cout << "Discounted Price: "; cin >> price; return price; } int readStockAmount(){ int amount; cout << "Stock Amount: "; cin >> amount; return amount; } void readonebook(int* isbn, char* author, char* title, char* publisher, int* edition, int* year, int* pages, float* msrp, float* discounted, int* inventory){ *isbn = readIsbn(); author = readAuthor(); title = readTitle(); publisher = readPublisher(); *edition = readEdition(); *year = readYear(); *pages = readPages(); *msrp = readMsrp(); *discounted = readDiscountedPrice(); *inventory = readStockAmount(); }

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  • Dynamic allocated array is not freed

    - by Stefano
    I'm using the code above to dynamically allocate an array, do some work inside the function, return an element of the array and free the memory outside of the function. But when I try to deallocate the array it doesn't free the memory and I have a memory leak. The debugger pointed to the myArray variable shows me the error CXX0030. Why? struct MYSTRUCT { char *myvariable1; int myvariable2; char *myvariable2; .... }; void MyClass::MyFunction1() { MYSTRUCT *myArray= NULL; MYSTRUCT *myElement = this->MyFunction2(myArray); ... delete [] myArray; } MYSTRUCT* MyClass::MyFunction2(MYSTRUCT *array) { array = (MYSTRUCT*)operator new(bytesLength); ... return array[X]; }

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  • C++ compilation error when passing a function into remove_if

    - by garsh0p
    So here's a snippet of my code. void RoutingProtocolImpl::removeAllInfinity() { dv.erase(std::remove_if(dv.begin(), dv.end(), hasInfCost), dv.end()); } bool RoutingProtocolImpl::hasInfCost(RoutingProtocolImpl::dv_entry *entry) { if (entry-link_cost == INFINITY_COST) { free(entry); return true; } else { return false; } } I'm getting the following error when compiling: RoutingProtocolImpl.cc:368: error: argument of type bool (RoutingProtocolImpl::)(RoutingProtocolImpl::dv_entry*)' does not matchbool (RoutingProtocolImpl::*)(RoutingProtocolImpl::dv_entry*)' Sorry, I'm kind of a C++ newb.

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