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  • C++ Memory allocation question involving vectors

    - by TheFuzz
    vector< int > vect; int *int_ptr = new int(10); vect.push_back( *int_ptr ); I under stand that every "new" needs to be followed by a "delete" at some point but does the clear() method clean this memory? What about this method of doing the same thing: vector< int > vect; int int_var = 10; vect.push_back( int_var ); From what I understand, clear() calls the variables destructors, but both vect.push_back() methods in this example push an object on the vector, not a pointer. so does the first example using an int pointer need something other than clear() to clean up memory?

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  • Objective-C: how to splt a string constant across multiple lines

    - by Ilya
    Hi, I have a pretty long sqlite query: const char *sql_query = "SELECT statuses.word_id FROM lang1_words, statuses WHERE statuses.word_id = lang1_words.word_id ORDER BY lang1_words.word ASC"; How can I break it in a number of lines to make it easier to read? If I do the following: const char *sql_query = "SELECT word_id FROM table1, table2 WHERE table2.word_id = table1.word_id ORDER BY table1.word ASC"; I am getting a error. Is there a way to write queries in multiple lines? Thank you.

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  • c++ fread changing fgetpos strangely

    - by Steve
    If I run: FILE* pFile = fopen("c:\\08.bin", "r"); fpos_t pos; char buf[5000]; int ret = fread(&buf, 1, 9, pFile); fgetpos(pFile, &pos); I get ret = 9 and pos = 9. However if I run FILE* pFile = fopen("c:\\08.bin", "r"); fpos_t pos; char buf[5000]; int ret = fread(&buf, 1, 10, pFile); fgetpos(pFile, &pos); ret = 10 as expected, but pos = 11! How can this be?

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  • g++ no matching function call error

    - by gufftan
    I've got a compiler error but I can't figure out why. the .hpp: #ifndef _CGERADE_HPP #define _CGERADE_HPP #include "CVektor.hpp" #include <string> class CGerade { protected: CVektor o, rv; public: CGerade(CVektor n_o, CVektor n_rv); CVektor getPoint(float t); string toString(); }; the .cpp: #include "CGerade.hpp" CGerade::CGerade(CVektor n_o, CVektor n_rv) { o = n_o; rv = n_rv.getUnitVector(); } the error message: CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&) CGerade.cpp:10: error: no matching function for call to ‘CVektor::CVektor()’ CVektor.hpp:28: note: candidates are: CVektor::CVektor(float, float, float) CVektor.hpp:26: note: CVektor::CVektor(bool, float, float, float) CVektor.hpp:16: note: CVektor::CVektor(const CVektor&)

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  • PHP , What is the difference between fopen r+ and r ! does it matter if i used r+ when not intending

    - by Naughty.Coder
    when I use fopen function , why don't I use r+ always , even when I'm not going to write any thing ... is there a reason for separating writing/reading process from only reading .. like , the file is locked for reading when I use r+ , because i might write new data into it or something ... another question : in php manual a+ : Open for reading and writing; place the file pointer at the end of the file. If the file does not exist, attempt to create it. What is supposed to be read if you are at the end of the file ..(pointer at the end) !!? where to learn more about the filesystem thing .... it's confusing

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  • c++: truth assignment warning with arguments?

    - by John
    I use the following to work with arguments in my programs, but it seems to just hand me a warning (just a warning): "warning: suggest parentheses around assignment used as truth value" The beginning of the code is as follows: enum{OPT_DISP_H = 0x2, OPT_DISP_W = 0x1}; int main(int argc, char *argv[]) { int opt = 0x00; char c; while((++argv)[0] && argv[0][0]=='-'){ while(c =* ++argv[0]) switch(c){ case 'h': opt |= OPT_DISP_H; break; //etc.. The while(c =* ++argv[0]) part being where the warning persists. The code works fine, but what does this warning mean opposed to what is used? I think the code is c = *++argv[0], using the pointer. So why does the single = work and what is really recommended to be used?

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  • Using sizeof with a dynamically allocated array

    - by robUK
    Hello, gcc 4.4.1 c89 I have the following code snippet: #include <stdlib.h> #include <stdio.h> char *buffer = malloc(10240); /* Check for memory error */ if(!buffer) { fprintf(stderr, "Memory error\n"); return 1; } printf("sizeof(buffer) [ %d ]\n", sizeof(buffer)); However, the sizeof(buffer) always prints 4. I know that a char* is only 4 bytes. However, I have allocated the memory for 10kb. So shouldn't the size be 10240? I am wondering am I thinking right here? Many thanks for any suggestions,

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  • Perl : How to print all cp1252 characters on by one ?

    - by Vinay
    Hi,i am not able to write a script to print all the latin -1 characters one by one.Can anybody help me in solving the problem? I am using the below code but it is not giving me expected result. foreach $char(0..255) { $hexval = sprintf("%x",$char); $charval = sprintf("%c",%hexval); print "$charval"; } output should be like :- 0065 - e 0066 - f ... ... 007F - character at the step For all the codepoints after 007F,it is not giving me expected results. Please help me out with this

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  • Class basic operators

    - by swan
    Hi, Is it necessary to have a copy constructor, destructor and operator= in a class that have only static data member, no pointer class myClass{ int dm; public: myClass(){ dm = 1; } ~myClass(){ } // Is this line usefull ? myClass(const myClass& myObj){ // and that operator? this->dm = myObj.dm; } myClass& operator=(const myClass& myObj){ // and that one? if(this != &myObj){ this->dm = myObj.dm; } return *this; } }; I read that the compiler build one for us, so it is better to not have one (when we add a data member we have to update the operators)

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  • Copy unmanaged data into managed array

    - by JeffRSon
    I need to copy native (i.e. unmanaged) data (byte*) to managed byte array with C++/CLI (array). I tried Marshal::Copy (data is pointed to by const void* data and is dataSize bytes) array<byte>^ _Data=gcnew array<byte>(dataSize); System::Runtime::InteropServices::Marshal::Copy((byte*)data, _Data, 0, dataSize); This gives error C2665: none of the 16 overloads can convert all parameters. Then I tried System::Runtime::InteropServices::Marshal::Copy(new IntPtr(data), _Data, 0, dataSize); which produces error C2664: parameter 1 cannot be converted from "const void*" to "__w64 int". So how can it be done and is Marshal::Copy indeed the "best" (simplest/fastest) way to do so?

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  • How is push()ing and pop()ping defined?

    - by Helper Method
    I know how the push() and pop() methods in a typical implementation of a Queue/Linked List work but what I do want to know is what you actually define as a push or a pop? When can you name a method push()/pop()? What makes the insert()/add() method in a typical Tree implementation not a push()? My understanding is that push()ing means putting something to a position some special pointer is pointing to, and pop()ping an element means putting some object away some pointer is pointing to, but it doesn't seem to be clearly defined. Or does the naming matter at all?

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  • Sort an array via x86 Assembly (embedded in C++)?? Possible??

    - by Mark V.
    I am playing around with x86 assembly for the first time and I can't figure out how to sort an array (via insertion sort).. I understand the algorithm, but assembly is confusing me as I primarily use Java & C++. Heres all I have so far int ascending_sort( char arrayOfLetters[], int arraySize ) { char temp; __asm{ push eax push ebx push ecx push edx push esi push edi //// ??? pop edi pop esi pop edx pop ecx pop ebx pop eax } } Basically nothing :( Any ideas?? Thanks in advance.

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  • How to access constant defined in child class?

    - by kavoir.com
    I saw this example from php.net: <?php class MyClass { const MY_CONST = "yonder"; public function __construct() { $c = get_class( $this ); echo $c::MY_CONST; } } class ChildClass extends MyClass { const MY_CONST = "bar"; } $x = new ChildClass(); // prints 'bar' $y = new MyClass(); // prints 'yonder' ?> But $c::MY_CONST is only recognized in version 5.3.0 or later. The class I'm writing may be distributed a lot. Basically, I have defined a constant in ChildClass and one of the functions in MyClass (father class) needs to use the constant. Any idea?

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  • Singly-Linked Lists insert_back and isIncreasing

    - by rezivor
    I just finished writing a program that I can add, remove or print objects to a list, but I am having difficulty implementing two more functions that is insert_back, which inserts a value to the end of a list. Also,I have to modify the representation of a List and alter whatever methods are necessary to make insert_back run in constant time: O(1). This new operation should have the signature: void List::insert_back( const Object& data ); Also, isIncreasing, For example, for a list containing head-() (11) (8) (15) (3), isIncreasing() should return false. However, it would return true when working on a list containing head- () (7) (9) (15). This new operation should have the signature: bool List::isIncreasing() const; Thank you

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  • zeroing out memory

    - by robUK
    Hello, gcc 4.4.4 c89 I am just wondering what most c programmers do when they want to zero out memory. For example I have a buffer of 1024 bytes. Sometimes I do this: char buffer[1024] = {0}; Which will zero all bytes. However, should I declare like this and use memset? char buffer[1024]; . . memset(buffer, 0, sizeof(buffer); Is there any real reason you have to zero the memory? What is the worst that can happen by not doing it? Many thanks for any suggestions,

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  • syntax error : missing ';' before identifier

    - by numerical25
    I am new to c++, trying to debug the following line of code class cGameError { string m_errorText; public: cGameError( char *errorText ) { DP1("***\n*** [ERROR] cGameError thrown! text: [%s]\n***\n", errorText ); m_errorText = string( errorText ); } const char *GetText() { return m_errorText.c_str(); } }; enum eResult { resAllGood = 0, // function passed with flying colors resFalse = 1, // function worked and returns 'false' resFailed = –1, // function failed miserably resNotImpl = –2, // function has not been implemented resForceDWord = 0x7FFFFFFF }; This header file is included in the program as followed #include "string.h" #include "stdafx.h" #include "Chapter 01 MyVersion.h" #include "cGameError.h"

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  • Sending while receiving in C

    - by Spidfire
    I've made a piece of code in what's on my server, the problem is that it doesn't send while im receiving. so if i send something to client 1 to client 2, client2 only receives if he sends something himself.. how can i solve this ? /* Thread*/ while (! stop_received) { nr_bytes_recv = recv(s, buffer, BUFFSIZE, 0); if(strncmp(buffer, "SEND", 4) == 0) { char *message = "Text asads \n"; rv = send(users[0].s, message, strlen(message), 0); rv = send(users[1].s, message, strlen(message), 0); if (rv < 0) { perror("Error sending"); exit(EXIT_FAILURE); } }else{ char *message = "Unknown command \n"; rv = send(s, message, strlen(message), 0); if (rv < 0) { perror("Error sending"); exit(EXIT_FAILURE); } } }

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  • explain this macro

    - by deostroll
    #define __T(x) L ## x Found in code from one of the MFC source header file. It is mostly used for converting strings to ........ (I don't know what). If I am correct it converts strings to LPCTSTR...don't know what that type is either... I can't seem to convert char* into LPCTSTR. While MFC file handling, the following code will always return error while trying to open the file... char* filepath = "C:\\Program Files\\Microsoft Office\\Office12\\BITMAPS\\STYLES\\GLOBE.WMF"; if( !file.Open((LPCTSTR)filepath , CFile::modeRead, &fexp) ) { fexp.ReportError(); return 1; } But instead if I wrote it this way, it doesn't give error: if( !file.Open( _T("C:\\Program Files\\Microsoft Office\\Office12\\BITMAPS\\STYLES\\GLOBE.WMF") , CFile::modeRead, &fexp) ) { fexp.ReportError(); return 1; } I am looking at passing a variable as the first argument to the CFile::Open() method.

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  • C++: Throwing shared_ptr of derived and catching shared_ptr of base?

    - by hasvn
    Ok, I've been told this problem: Why can you throw a pointer to a derived class and catch a pointer to its base... but you can't do that with shared_ptrs? Example, this works: class Base {}; class Derived : public Base {}; int main() { try { throw new Derived() ; } catch( const Base2 * b ) { printf("Received a base" ) ; } return 0 ; } But this doesn't int main() { try { throw std::tr1::shared_ptr<Derived>( new Derived() ) ; } catch( const std::tr1::shared_ptr<Base> & b ) { printf("Received a base" ) ; } return 0 ; } Any ideas?

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  • Referencing invalid memory locations with C++ Iterators

    - by themoondothshine
    I am a big fan of GCC, but recently I noticed a vague anomaly. Using __gnu_cxx::__normal_iterator (ie, the most common iterator type used in libstdc++, the C++ STL) it is possible to refer to an arbitrary memory location and even change its value without causing an exception! Is this expected behavior? If so, isn't a security loophole? Here's an example: #include <iostream> using namespace std; int main() { basic_string<char> str("Hello world!"); basic_string<char>::iterator iter = str.end(); iter += str.capacity() + 99999; *iter = 'x'; cout << "Value: " << *iter << endl; }

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  • hash table with chaining method program freezing

    - by Justin Carrey
    I am implementing hash table in C using linked list chaining method. The program compiles but when inserting a string in hash table, the program freezes and gets stuck. The program is below: struct llist{ char *s; struct llist *next; }; struct llist *a[100]; void hinsert(char *str){ int strint, hashinp; strint = 0; hashinp = 0; while(*str){ strint = strint+(*str); } hashinp = (strint%100); if(a[hashinp] == NULL){ struct llist *node; node = (struct llist *)malloc(sizeof(struct llist)); node->s = str; node->next = NULL; a[hashinp] = node; } else{ struct llist *node, *ptr; node = (struct llist *)malloc(sizeof(struct llist)); node->s = str; node->next = NULL; ptr = a[hashinp]; while(ptr->next != NULL){ ptr = ptr->next; } ptr->next = node; } } void hsearch(char *strsrch){ int strint1, hashinp1; strint1 = 0; hashinp1 = 0; while(*strsrch){ strint1 = strint1+(*strsrch); } hashinp1 = (strint1%100); struct llist *ptr1; ptr1 = a[hashinp1]; while(ptr1 != NULL){ if(ptr1->s == strsrch){ cout << "Element Found\n"; break; } else{ ptr1 = ptr1->next; } } if(ptr1 == NULL){ cout << "Element Not Found\n"; } } hinsert() is to insert elements into hash and hsearch is to search an element in the hash. Hash function is written inside hinsert() itself. In the main(), what i am initializing all the elements in a[] to be NULL like this: for(int i = 0;i < 100; i++){ a[i] = NULL; } Help is very much appreciated. Thanks !

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  • Second query to SQLite (on iPhone) errors.

    - by Luke
    Hi all, On the iPhone, I am developing a class for a cart that connects directly to a database. To view the cart, all items can be pulled from the database, however, it seems that removing them doesn't work. It is surprising to me because the error occurs during connection to the database, except not the second time I connect even after the DB has been closed. #import "CartDB.h" #import "CartItem.h" @implementation CartDB @synthesize database, databasePath; - (NSMutableArray *) getAllItems { NSMutableArray *items = [[NSMutableArray alloc] init]; if([self openDatabase]) { const char *sqlStatement = "SELECT * FROM items;"; sqlite3_stmt *compiledStatement; if(sqlite3_prepare_v2(cartDatabase, sqlStatement, -1, &compiledStatement, NULL) == SQLITE_OK) { while(sqlite3_step(compiledStatement) == SQLITE_ROW) { int rowId = sqlite3_column_int(compiledStatement, 0); int productId = sqlite3_column_int(compiledStatement, 1); NSString *features = [NSString stringWithUTF8String:(char *)sqlite3_column_text(compiledStatement, 2)]; int quantity = sqlite3_column_int(compiledStatement, 3); CartItem *cartItem = [[CartItem alloc] initWithRowId:rowId productId:productId features:features quantity:quantity]; [items addObject:cartItem]; [cartItem release]; } } sqlite3_finalize(compiledStatement); } [self closeDatabase]; return items; } - (BOOL) removeCartItem:(CartItem *)item { sqlite3_stmt *deleteStatement; [self openDatabase]; const char *sql = "DELETE FROM items WHERE id = ?"; if(sqlite3_prepare_v2(cartDatabase, sql, -1, &deleteStatement, NULL) != SQLITE_OK) { return NO; } sqlite3_bind_int(deleteStatement, 1, item.rowId); if(SQLITE_DONE != sqlite3_step(deleteStatement)) { sqlite3_reset(deleteStatement); [self closeDatabase]; return NO; } else { sqlite3_reset(deleteStatement); [self closeDatabase]; return YES; } } - (BOOL) openDatabase { if(sqlite3_open([databasePath UTF8String], &cartDatabase) == SQLITE_OK) { return YES; } else { return NO; } } - (void) closeDatabase { sqlite3_close(cartDatabase); } The error occurs on the line where the connection is opened in openDatabase. Any ideas? Need to flush something? Something gets autoreleased? I really can't figure it out. --Edit-- The error that I receive is GDB: Program received signal "EXC_BAD_ACCESS". --Edit-- I ended up just connecting in the init and closing in the free methods, which might not be the proper way, but that's another question altogether so it's effectively persistent instead of connecting multiple times. Still would be nice to know what was up with this for future reference.

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  • Problem with Initializing Consts

    - by UdiM
    This code, when compiled in xlC 8.0 (on AIX 6.1), produces the wrong result. It should print 12345, but instead prints 804399880. Removing the const in front of result makes the code work correctly. Where is the bug? #include <stdio.h> #include <stdlib.h> #include <string> long int foo(std::string input) { return strtol(input.c_str(), NULL, 0); } void bar() { const long int result = foo("12345"); printf("%u\n", result); } int main() { bar(); return 0; } Compilation command: /usr/vacpp/bin/xlC example.cpp -g

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  • How do I compare vectors in C++?

    - by Sam Phelps
    I am trying to compare two vector objects, and return a single vector containing all the chars which appear in both vectors. How would I go about this without writing some horribly complex manual method which compares every char in the first vector to every char in the second vector and using an if to add it to a third vector (which would be returned) if they match. Maybe my lack of real experience with vectors is making me imagine this will be harder than it really is, but I suspect there is some simplier way which I have been unable to find through searching.

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  • C++: Vector3 type "wall" ?

    - by anon
    Say I have: class Vector3 { float x, y, z; ... bunch of cuntions .. static operator+(const Vector3&, const Vector3); }; Now, suppose I want to have classes: Position, Velocity, that are exactly like Vector3 (basically, I want typedef Vector3 Position; typedef Vector3 Velocity; Except, given: Position position; Vector3 vector3; Velocity velocity; I want to make sure the following can't happen: position + vector3; vector3 + velocity; velocity + position; What is the best way to achieve this?

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