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Opening and closing braces for if, for, or while statements should always be used, even if said the statement's body contains only a single statement.

If an if, while, or for statement is used in a macro, then the macro definition should not be concluded conclude with a semicolon. (See guideline PRE11-C. Do not conclude macro definitions with a semicolon.)

Braces help improve the uniformity and readability of code.

More importantly, when inserting an additional statement in into a body containing only a single statement, it is easy to forget to add braces when because the indentation tends to give a gives strong (but misleading) guide guidance to the structure.

Braces also help ensure that macros with multiple statements are properly expanded. Such a macro should be wrapped in a do-while loop. (See guideline PRE10-C. Wrap multi-statement macros in a do-while loop.) However, when the do-while loop is not present, braces can still ensure that the macro expands as intended.

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Due to the indentation of the code, it is difficult to tell that the code will not function as intended by the programmer, potentially leading to a possible security breach.

Compliant Solution

Opening In the compliant solution, opening and closing braces are used even when the body is a single statement.

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Noncompliant Code Example

When you have This noncompliant code example has an if statement nested in another if statement , always put without braces around if and else bodies.This noncompliant

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int privileges;

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

According to the indentation, The indentation could lead the programmer may be led to believe that a user is given administrator privileges only when his the user's login is valid. However, in reality, the else statement actually attaches to the inner if statement:

int privileges;

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

This is a security loophole—users loophole: users with invalid logins can still obtain administrator privileges.

Compliant Solution

Adding In the compliant solution, adding braces removes the ambiguity and ensures that privileges are correctly assigned.

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\[[ISO/IEC 9899-:1999|AA. Bibliography#ISO/IEC 9899-1999]\] Section 6.8.4, "Selection statements"
\[[MISRA 2004|AA. Bibliography#MISRA 04]\] Rule 14.8
\[[GNU 2010|AA. Bibliography#GNU 10]\] [Coding Standards, Section 5.3, "Clean Use of C Constructs"|http://www.gnu.org/prep/standards/standards.html#Syntactic-Conventions]\] Section 5.3, "Clean Use of C Constructs"

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EXP18-C. Do not perform assignments in selection statements      03. Expressions (EXP)      EXP20-C. Perform explicit tests to determine success, true-false, and equality