Programming Articles - Page 3199 of 3366

C++ has header and .ccp files for separating the interface from the implementation. The header files declare "what" a class (or whatever is being implemented) will do, ie the API of the class, kind of like an interface in Java. The cpp file on the other hand defines "how" it will perform those features, ie, the implementation of these declared functionality.This reduces dependencies. The code that uses the header doesn't need to know all the details of the implementation and any other classes/headers needed only for that. It just needs to focus on things it is trying to implement. This ... Read More

In C++, calling a virtual function inside a constructor or destructor is dangerous and should generally be avoided. Following are the reasons to avoid calling: When a constructor (or destructor) is running, the object is not fully built (or fully destroyed). At that time, the virtual function table (vtable) points to the version of the class currently being constructed or destructed, not the most derived version. What Happens When You Call a Virtual Function in a Constructor? If you call the virtual function inside a constructor: ... Read More

A segmentation fault occurs when your program attempts to access an area of memory that it is not allowed to access. In other words, when your program tries to access memory that is beyond the limits that the operating system allocated for your program.Seg faults are mostly caused by pointers that are −Used to being properly initialized.Used after the memory they point to has been reallocated or freed.Used in an indexed array where the index is outside of the array bounds.

A process dumps core when it is terminated by the operating system due to a fault in the program. The most typical reason this occurs is that the program accessed an invalid pointer value like NULL or some value out of its memory area. As part of that process, the operating system tries to write our information to a file to allow us to analyze what happened.This core can be used as follows to diagnose and debug our program −The core is dumped to the /proc/sys/kernel directory by default. To debug a core, the program must be compiled with the ... Read More

The explicit keyword in C++ is used to mark constructors to not implicitly convert types. For example, if you have a class Foo −class Foo { public:     Foo(int n); // allocates n bytes to the Foo object     Foo(const char *p); // initialize object with char *p };Now if you tryFoo mystring = 'x';The char 'x' is implicitly converted to int and then will call the Foo(int) constructor. But this is not what was intended. So to prevent such conditions and make the code less error-prone, define the constructor as explicit −Example class Foo {    public:   ... Read More

You can use the itoa function from C to convert an int to string.  example#include int main() {    int a = 10;    char *intStr = itoa(a);    string str = string(intStr);    cout

Standard C++ doesn't provide a way to do this. You could use the system command to initialize the ls command as follows −Example#include int main () {    char command[50] = "ls -l";    system(command);    return 0; }OutputThis will give the output −-rwxrwxrwx 1 root root  9728 Feb 25 20:51 a.out -rwxrwxrwx 1 root root   131 Feb 25 20:44 hello.cpp -rwxrwxrwx 1 root root   243 Sep  7 13:09 hello.py -rwxrwxrwx 1 root root 33198 Jan  7 11:42 hello.o drwxrwxrwx 0 root root   512 Oct  1 21:40 hydeout -rwxrwxrwx 1 root root    42 Oct 21 11:29 ... Read More

Undefined behavior is a way to give freedom to implementors (e.g. of compilers or of OSes) and to computers to do whatever they "want", in other words, to not care about consequences.The cases in which segmentation fault occurs are transient in nature. They won't always result in a segmentation fault but can also run correctly(or at least appear to). For example, consider the following code fragment −#include int main() {     int arr[2];     arr[0] = 0;     arr[1] = 1;     arr[2] = 2; // Undefined behaviour     arr[3] = 3; // Undefined behaviour ... Read More

You can sort a vector of custom objects using the C++ STL function std::sort. The sort function has an overloaded form that takes as arguments first, last, comparator. The first and last are iterators to first and last elements of the container. The comparator is a predicate function that can be used to tell how to sort the container. example#include #include #include using namespace std; struct MyStruct {    int key;    string data;    MyStruct(int key, string data) {       this -> key = key;       this -> data = data;    } }; int ... Read More

You can use the popen and pclose functions to pipe to and from processes. The popen() function opens a process by creating a pipe, forking, and invoking the shell. We can use a buffer to read the contents of stdout keep appending it to a result string and return this string when the processes exit. Example Here is the following example showing an execution of a command and getting the output of the command within C++ using POSIX. #include #include #include #include using namespace std; string exec(const string& command) {  char buffer[128];  string result ... Read More