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Use opening and closing braces for if, for, and while statements even when the body contains only a single statement. Braces improve the uniformity and readability of code.

More important, it is easy to forget to add braces when inserting additional statements into a body containing only a single statement, because the conventional indentation gives strong (but misleading) guidance to the structure.

Noncompliant Code Example

This noncompliant code example authenticates a user with an if statement that lacks braces:

int login;

if (invalid_login())
  login = 0;
else
  login = 1;

This program behaves as expected. However, a maintainer might subsequently add a debug statement or other logic but forget to add opening and closing braces:

int login;

if (invalid_login())
  login = 0;
else
  // Debug line added below
  System.out.println("Login is valid\n");
  // The next line is always executed 
  login = 1; 

The code's indentation disguises the functionality of the program, potentially leading to a security breach.

Compliant Solution

This compliant solution uses opening and closing braces even though the body of the if and else bodies of the if statement are single statements:

int login;

if (invalid_login()) {
  login = 0;
} else {
  login = 1;
}

Noncompliant Code Example

This noncompliant code example nests an if statement within another if statement, without braces around the if and else bodies:

int privileges;

if (invalid_login())
  if (allow_guests())
    privileges = GUEST;
else
  privileges = ADMINISTRATOR;

The indentation might lead the programmer to believe users are granted administrator privileges only when their login is valid. However, the else statement actually binds to the inner if statement:

int privileges;

if (invalid_login())
  if (allow_guests())
    privileges = GUEST;
  else
    privileges = ADMINISTRATOR;

Consequently, this defect allows unauthorized users to obtain administrator privileges.

Compliant Solution

This compliant solution uses braces to remove the ambiguity, consequently ensuring that privileges are correctly assigned:

int privileges;

if (invalid_login()) {
  if (allow_guests()) {
    privileges = GUEST;
  } 
} else {
  privileges = ADMINISTRATOR;
}

Applicability

Failure to enclose the bodies of if, for, or while statements in braces makes code error prone and increases maintenance costs.

Automated Detection

ToolVersionCheckerDescription
SonarQube Java Plugin
Unable to render {include} The included page could not be found.

S2681
S00121

 

 

Bibliography

 


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