C++ goto statement


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A goto statement provides an unconditional jump from the goto to a labeled statement in the same function.

NOTE: Use of goto statement is highly discouraged because it makes difficult to trace the control flow of a program, making the program hard to understand and hard to modify. Any program that uses a goto can be rewritten so that it doesn't need the goto.

Syntax

The syntax of a goto statement in C++ is:

goto label;
..
.
label: statement;

Where label is an identifier that identifies a labeled statement. A labeled statement is any statement that is preceded by an identifier followed by a colon (:).

Flow Diagram

C++ goto statement

Example

#include <iostream>
using namespace std;
 
int main () {
   // Local variable declaration:
   int a = 10;

   // do loop execution
   LOOP:do {
      if( a == 15) {
         // skip the iteration.
         a = a + 1;
         goto LOOP;
      }
		
      cout << "value of a: " << a << endl;
      a = a + 1;
   }while( a < 20 );
 
   return 0;
}

When the above code is compiled and executed, it produces the following result:

value of a: 10
value of a: 11
value of a: 12
value of a: 13
value of a: 14
value of a: 16
value of a: 17
value of a: 18
value of a: 19

One good use for the goto is to exit from a deeply nested routine. For example, consider the following code fragment:

for(...) {
   for(...) {
      while(...) {
         if(...) goto stop;
         .
         .
         .
      }
   }
}
stop:
cout << "Error in program.\n";

Eliminating the goto would force a number of additional tests to be performed. A simple break statement would not work here, because it would only cause the program to exit from the innermost loop.


cpp_loop_types.htm

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