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

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Braces also help ensure that macros with multiple statements are properly expanded. Such a macro should be wrapped in a do-while loop. (See PRE10-C. Wrap multistatement 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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int login;

if (invalid_login())
  login = 0;
else
  printf("Login is valid\n");  /* debuggingDebugging line added here */
  login = 1;                   /* thisThis line always gets executed, regardless of a valid login! */

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