Curly Braces in C++ Best Practices

In C/C++, omitting the curly braces assumes that only the first statement is the block and this leads to quite a few issues during debugging, as code is pretty tough to read and comprehend. Curly braces help us prevent errors and confusion, which also helps with the flow of the program.

Proper Use of Curly Braces

In C++, we can omit the curly braces after if-else statements, or after any loop. If we do not use curly braces, then only one statement after the if-else or loop will be considered under that block.

Syntax

The following is the syntax: ?

if(condition) {
   Line 1
   Line 2
}
if(condition)
Line 1
Line 2

Example

In the following example, we check if the variable 'number' > 5. If the condition is true, it prints two specific messages. Regardless of the condition, it also prints another message outside the 'if' block.

#include <iostream>
using namespace std;
int main() {
   int number = 10;
   if (number > 5) {
      cout << "Number is greater than 5." << endl; // Part of the if block
      cout << "This will only execute if the condition is true." << endl;
   }
   cout << "This statement is outside the if block." << endl;
   return 0;
}

Output

Following is the output to the above program ?

Number is greater than 5.
This will only execute if the condition is true.
This statement is outside the if block.

Omitting Curly Braces - Leads to Confusion

In the first case, the Line1 and Line2 both are in the if block. But in the second condition, the Line1 is in if block but Line2 is not in if block. So we can omit curly braces only there is a single statement under if-else or loop.

Sometimes for debugging purpose we just make a line commented. Using this we check the effect of output without that statement. In that time the if-else or loops without braces makes some troubles.

if(condition) {
   Line 1
}
Line2
if(condition)
Line 1
Line 2

Example

Here, we are checking if number = 10 and that number 10 is greater than 5. If true, it prints "Number is greater than 5." There are no curly braces, the next statement executes the condition's result.

#include <iostream>
using namespace std;
int main() {
   int number = 10;
   if (number > 5)
      cout << "Number is greater than 5." << endl; // Only this line is part of the if block
   cout << "This statement is always executed." << endl; // Not part of the if block
   return 0;
}

Output

Following is the output to the above program ?

Number is greater than 5.
This statement is always executed.

Debugging Issue Without Curly Braces

Here, in the both cases, the Line1 is in the if block but Line2 is not in the if block. So if the condition fails, or it satisfies the Line2 will be executed always. Now if the situation is like below for some debugging purpose, then it may generate some problems.

if(condition)
//Line 1
Line 2

Example

In this example, we check if the number 10 is greater than 5 and print a message about how missing curly braces can lead to ambiguity.  

#include <iostream>
using namespace std;
int main() {
   int number = 10;
   if (number > 5)
      // cout << "Debugging: Condition is true." << endl; // Temporarily commented out
      cout << "This line creates ambiguity when curly braces are missing." << endl;
   return 0;
}

Output

Following is the output to the above program ?

This line creates ambiguity when curly braces are missing.