What is unreachable code in c plus plus?

Answer 1

Unreachable code is code that can never execute. It usually happens when you have a logic error in your code, such as when an if condition always evaluates true (or false). For example:

int foo(int& x)

{

if( &x == NULL ) // always evaluates false...

{

// Unreachable code:

std::err<<"int foo(int&) : argument int& is a NULL reference"<<std::endl;

return(-1);

}

return(0);

}

In the above example, the entire if() statement is redundant because the argument, x, is a reference. In C++, references can never be NULL, so the if statement can never evaluate true. Furthermore, in this particular example, the entire function can be said to be redundant (but not unreachable), simply because it serves no purpose. It will always return zero.