MISRA.SWITCH.NOT_WELL_FORMED

Switch statement is not well-formed.

MISRA-C++ Rule 6-4-3 (required): A switch statement shall be a well-formed switch statement.

A well-formed switch statement conforms to the following syntax rules, which are additional to the C++ standard syntax rules. All syntax rules not defined below are as defined in ISO/IEC 14882:2003 [1].

switch-statement:

switch ( condition ) { case-label-clause-list default-label-clauseopt }

case-label-clause-list:

case-label case-clauseopt

case-label-clause-list case-label case-clauseopt

case-label:

case constant-expression :

case-clause:

case-block-seqopt break ;

case-block-seqopt throw assignment-expressionopt ;

{ statement-seqopt break ; }

{ statement-seqopt throw assignment-expressionopt ; }

default-label-clause:

default-label default-clause

default-label:

default :

default-clause:

case-clause

case-block:

expression_statement

compound_statement

selection_statement

iteration_statement

try_block

case-block-seq:

case-block

case-block-seq case-block

The following statements, which are permitted by C++, are explicitly not included within the MISRA C++ switch syntax rules. Note, however, that they are permitted within the compound statements forming the body of a switch-clause.

labelled_statement

jump_statement

declaration_statement

The following terms are also used within the text of the rules:

switch-label Either a case-label or default-label. case-clause The code between any two switch-labels. default-clause The code between the default-label and the end of the switch statement. switch-clause Either a case-clause or a default-clause.

Rationale

The syntax for the switch statement in C++ is weak, allowing complex, unstructured behaviour. The previous text describes the syntax for switch statements as defined by MISRA C++. This, and the associated rules, imposes a simple and consistent structure on to the switch statement.

Example

switch ( x )
{
case 0:
   ...
   break;  // break is required here
case 1:    // empty clause, break not required
case 2:
   break;  // break is required here
default:   // default clause is required
   break;  // break is required here, in case a future
           // modification turns this into a case clause
}