Programming Articles - Page 2641 of 3363

Here we will see the Hygienic Macros in C. We know the usage of macros in C. But sometimes, it does not return the desired results because of accidental capture of identifiers.If we see the following code, we can see that it is not working properly.Example#include #define INCREMENT(i) do { int a = 0; ++i; } while(0) main(void) {    int a = 10, b = 20;    //Call the macros two times for a and b    INCREMENT(a);    INCREMENT(b);    printf("a = %d, b = %d", a, b); }After preprocessing the code will be like this −Example#include #define ... Read More

Here we will see some incompatibilities between C and C++. Some C codes that can be compiled using C compiler, but does not compile in C++ compiler. And also returns error.We can define function using a syntax, that optionally specify the argument types after the argument list.Example#include void my_function(x, y)int x;int y; { // Not valid in C++    printf("x = %d, y = %d", x, y); } int main() {    my_function(10, 20); }Outputx = 10, y = 20OutputError in C++ :- x and y was not declared in this scopeIn C, or some older version of C++, the ... Read More

Here we will see the effect of fork() and exec() system call in C. The fork is used to create a new process by duplicating the calling process. The new process is the child process. See the following property.The child process has its own unique process id.The parent process id of the child process is same as the process id of the calling process.The child process does not inherit the parent’s memory lock and semaphores.The fork() returns the PID of the child process. If the value is non-zero, then it is parent process’s id, and if this is 0, then ... Read More

Here we will see what will be the effect of pthread_self() in C. The pthread_self() function is used to get the ID of the current thread. This function can uniquely identify the existing threads. But if there are multiple threads, and one thread is completed, then that id can be reused. So for all running threads, the ids are unique.Example#include #include #include void* func(void* p) {    printf("From the function, the thread id = %d", pthread_self()); //get current thread id       pthread_exit(NULL);    return NULL; } main() {    pthread_t thread; // declare thread   ... Read More

The pthread_equal() function is used to check whether two threads are equal or not. This returns 0 or non-zero value. For equal threads, it will return non-zero, otherwise it returns 0. The syntax of this function is like below −int pthread_equal (pthread_t th1, pthread_t th2);Now let us see the pthread_equal() in action. In the first case, we will check the self-thread to check the result.Example#include #include #include #include #include pthread_t sample_thread; void* my_thread_function(void* p) {    if (pthread_equal(sample_thread, pthread_self())) { //pthread_self will return current thread id       printf("Threads are equal");    } else ... Read More

The threa_cancel() is used to cancel one particular thread by the thread id. This function sends one cancellation request to the thread for termination. The syntax of the pthread_cancel() is like below −int pthread_cancel(pthread_t th);Now, let us see how to cancel threads using this function.Example#include #include #include #include int count = 0; pthread_t sample_thread; void* thread_one_func(void* p) {    while (1) {       printf("This is thread 1");       sleep(1); // wait for 1 seconds       count++;       if (count == 5) {          //if the ... Read More

Here we will see the effect of nextafter() and nextforward() functions in C or C++. These functions are present in the math.h or cmath library.if the functions are like nextafter(a, b) and nextforward(a, b). These functions are used to find the next representable value after a in the direction of b. The nextforward() has more precise second parameter b.Example#include #include main () {    //The nextafter function()    printf ("Smallest representable number after 0 towards 1 : %e", nextafter(0.0, 1.0));    printf ("Largest representable number before -1 towards 0 :%e", nextafter(0.0, -1.0));    printf ("Largest +ve representable number ... Read More

Here we will see some interesting facts about C programming. These are like below.Sometimes the case labels of some switch statement can be placed inside if-else statement.Example#include main() {    int x = 2, y = 2;    switch(x) {       case 1:          ;          if (y==5) {             case 2:                printf("Hello World");          }          else case 3: {             //case 3 block       ... Read More

In C++, there is no direct way to check the environment architecture. There are two Macros for Windows systems, that can be used to check the architecture. These macros are _WIN64, and _WIN32. When the system is 64-bit, then the _WIN64 will be 1, otherwise the _WIN32 will be 1. So using macro checking, we can identify the architectureExample#include using namespace std; int main() {    #ifdef _WIN64       cout

A const member variable in a C++ class is a data member whose value must be initialized during object construction and cannot be modified. Initializing Const Member Variable in C++ Class The const member variable must be initialized. To initialize a const member variable, you can use a member initializer list using a constructor, . The member initializer list is the special way to initialize the values to class variables while creating an object before the constructor block runs. Note: If the member is static and of an integer type, you can directly initialized with the class definition. ... Read More