Appendix A Summary of guidelines Rule 1.1 Required The program shall contain no violations of the standard C syntax and constraints, and shall not exceed the implementation’s translation limits Rule 1.2 Advisory Language extensions should not be used Rule 1.3 Required There shall be no occurrence of undefined or critical unspecified behaviour Rule 2.1 Required A project shall not contain unreachable code Rule 2.2 Required There shall be no dead code Rule 2.3 Advisory A project should not contain unused type declarations Rule 2.4 Advisory A project should not contain unused tag declarations Rule 2.5 Advisory A project should not contain unused macro declarations Rule 2.6 Advisory A function should not contain unused label declarations Rule 2.7 Advisory There should be no unused parameters in functions Rule 3.1 Required The character sequences /* and // shall not be used within a comment Rule 3.2 Required Line-splicing shall not be used in // comments Rule 4.1 Required Octal and hexadecimal escape sequences shall be terminated Rule 4.2 Advisory Trigraphs should not be used Dir 4.3 Required Assembly language shall be encapsulated and isolated Dir 4.4 Advisory Sections of code should not be “commented out” Dir 4.5 Advisory Identifiers in the same name space with overlapping visibility should be typographically unambiguous Dir 4.6 Advisory typedefs that indicate size and signedness should be used in place of the basic numerical types Dir 4.7 Required If a function returns error information, then that error information shall be tested Dir 4.8 Advisory If a pointer to a structure or union is never dereferenced within a translation unit, then the implementation of the object should be hidden Dir 4.9 Advisory A function should be used in preference to a function-like macro where they are interchangeable Dir 4.10 Required Precautions shall be taken in order to prevent the contents of a header file being included more than once Dir 4.11 Required The validity of values passed to library functions shall be checked Dir 4.12 Required Dynamic memory allocation shall not be used Dir 4.13 Advisory Functions which are designed to provide operations on a resource should be called in an appropriate sequence Rule 5.1 Required External identifiers shall be distinct Rule 5.2 Required Identifiers declared in the same scope and name space shall be distinct Rule 5.3 Required An identifier declared in an inner scope shall not hide an identifier declared in an outer scope Rule 5.4 Required Macro identifiers shall be distinct Rule 5.5 Required Identifiers shall be distinct from macro names Rule 5.6 Required A typedef name shall be a unique identifier Rule 5.7 Required A tag name shall be a unique identifier Rule 5.8 Required Identifiers that define objects or functions with external linkage shall be unique Rule 5.9 Advisory Identifiers that define objects or functions with internal linkage should be unique Rule 6.1 Required Bit-fields shall only be declared with an appropriate type Rule 6.2 Required Single-bit named bit fields shall not be of a signed type Rule 7.1 Required Octal constants shall not be used Rule 7.2 Required A “u” or “U” suffix shall be applied to all integer constants that are represented in an unsigned type Rule 7.3 Required The lowercase character “l” shall not be used in a literal suffix Rule 7.4 Required A string literal shall not be assigned to an object unless the object’s type is “pointer to const-qualified char” Rule 8.1 Required Types shall be explicitly specified Rule 8.2 Required Function types shall be in prototype form with named parameters Rule 8.3 Required All declarations of an object or function shall use the same names and type qualifiers Rule 8.4 Required A compatible declaration shall be visible when an object or function with external linkage is defined Rule 8.5 Required An external object or function shall be declared once in one and only one file Rule 8.6 Required An identifier with external linkage shall have exactly one external definition Rule 8.7 Advisory Functions and objects should not be defined with external linkage if they are referenced in only one translation unit Rule 8.8 Required The static storage class specifier shall be used in all declarations of objects and functions that have internal linkage Rule 8.9 Advisory An object should be defined at block scope if its identifier only appears in a single function Rule 8.10 Required An inline function shall be declared with the static storage class Rule 8.11 Advisory When an array with external linkage is declared, its size should be explicitly specified Rule 8.13 Advisory A pointer should point to a const-qualified type whenever possible Rule 8.14 Required The restrict type qualifier shall not be used Rule 9.1 Mandatory The value of an object with automatic storage duration shall not be read before it has been set Rule 9.2 Required The initializer for an aggregate or union shall be enclosed in braces Rule 9.3 Required Arrays shall not be partially initialized Rule 9.4 Required An element of an object shall not be initialized more than once Rule 9.5 Required Where designated initializers are used to initialize an array object the size of the array shall be specified explicitly Rule 10.1 Required Operands shall not be of an inappropriate essential type Rule 10.2 Required Expressions of essentially character type shall not be used inappropriately in addition and subtraction operations Rule 10.3 Required The value of an expression shall not be assigned to an object with a narrower essential type or of a different essential type category Rule 10.4 Required Both operands of an operator in which the usual arithmetic conversions are performed shall have the same essential type category Rule 10.5 Advisory The value of an expression should not be cast to an inappropriate essential type Rule 10.6 Required The value of a composite expression shall not be assigned to an object with wider essential type Rule 10.7 Required If a composite expression is used as one operand of an operator in which the usual arithmetic conversions are performed then the other operand shall not have wider essential type Rule 10.8 Required The value of a composite expression shall not be cast to a different essential type category or a wider essential type Rule 11.1 Required Conversions shall not be performed between a pointer to a function and any other type Rule 11.2 Required Conversions shall not be performed between a pointer to an incomplete type and any other type Rule 11.3 Required A cast shall not be performed between a pointer to object type and a pointer to a different object type Rule 11.4 Advisory A conversion should not be performed between a pointer to object and an integer type Rule 11.5 Advisory A conversion should not be performed from pointer to void into pointer to object Rule 11.6 Required A cast shall not be performed between pointer to void and an arithmetic type Rule 11.7 Required A cast shall not be performed between pointer to object and a noninteger arithmetic type Rule 11.8 Required A cast shall not remove any const or volatile qualification from the type pointed to by a pointer Rule 11.9 Required The macro NULL shall be the only permitted form of integer null pointer constant Rule 12.1 Advisory The precedence of operators within expressions should be made explicit Rule 12.2 Required The right hand operand of a shift operator shall lie in the range zero to one less than the width in bits of the essential type of the left hand operand Rule 12.3 Advisory The comma operator should not be used Rule 12.4 Advisory Evaluation of constant expressions should not lead to unsigned integer wrap-around Rule 13.1 Required Initializer lists shall not contain persistent side effects Rule 13.2 Required The value of an expression and its persistent side effects shall be the same under all permitted evaluation orders Rule 13.3 Advisory A full expression containing an increment (++) or decrement (--) operator should have no other potential side effects other than that caused by the increment or decrement operator Rule 13.4 Advisory The result of an assignment operator should not be used Rule 13.5 Required The right hand operand of a logical && or || operator shall not contain persistent side effects Rule 13.6 Mandatory The operand of the sizeof operator shall not contain any expression which has potential side effects Rule 14.1 Required A loop counter shall not have essentially floating type Rule 14.2 Required A for loop shall be well-formed Rule 14.3 Required Controlling expressions shall not be invariant Rule 14.4 Required The controlling expression of an if statement and the controlling expression of an iteration-statement shall have essentially Boolean type Rule 15.1 Advisory The goto statement should not be used Rule 15.2 Required The goto statement shall jump to a label declared later in the same function Rule 15.3 Required Any label referenced by a goto statement shall be declared in the same block, or in any block enclosing the goto statement Rule 15.4 Advisory There should be no more than one break or goto statement used to terminate any iteration statement Rule 15.5 Advisory A function should have a single point of exit at the end Rule 15.6 Required The body of an iteration-statement or a selection-statement shall be a compound-statement Rule 15.7 Required All if … else if constructs shall be terminated with an else statement Rule 16.1 Required All switch statements shall be well-formed Rule 16.2 Required A switch label shall only be used when the most closely-enclosing compound statement is the body of a switch statement Rule 16.3 Required An unconditional break statement shall terminate every switch-clause Rule 16.4 Required Every switch statement shall have a default label Rule 16.5 Required A default label shall appear as either the first or the last switch label of a switch statement Rule 16.6 Required Every switch statement shall have at least two switch-clauses Rule 16.7 Required A switch-expression shall not have essentially Boolean type Rule 17.1 Required The features of shall not be used Rule 17.2 Required Functions shall not call themselves, either directly or indirectly Rule 17.3 Mandatory A function shall not be declared implicitly Rule 17.4 Mandatory All exit paths from a function with non-void return type shall have an explicit return statement with an expression Rule 17.5 Advisory The function argument corresponding to a parameter declared to have an array type shall have an appropriate number of elements Rule 17.6 Mandatory The declaration of an array parameter shall not contain the static keyword between the [ ] Rule 17.7 Required The value returned by a function having non-void return type shall be used Rule 17.8 Advisory A function parameter should not be modified Rule 18.1 Required A pointer resulting from arithmetic on a pointer operand shall address an element of the same array as that pointer operand Rule 18.2 Required Subtraction between pointers shall only be applied to pointers that address elements of the same array Rule 18.3 Required The relational operators >, >=, < and <= shall not be applied to objects of pointer type except where they point into the same object Rule 18.4 Advisory The +, -, += and -= operators should not be applied to an expression of pointer type Rule 18.5 Advisory Declarations should contain no more than two levels of pointer nesting Rule 18.6 Required The address of an object with automatic storage shall not be copied to another object that persists after the first object has ceased to exist Rule 18.7 Required Flexible array members shall not be declared Rule 18.8 Required Variable-length array types shall not be used Rule 19.1 Mandatory An object shall not be assigned or copied to an overlapping object Rule 19.2 Advisory The union keyword should not be used Rule 20.1 Advisory #include directives should only be preceded by preprocessor directives or comments Rule 20.2 Required The ', " or \ characters and the /* or // character sequences shall not occur in a header file name Rule 20.3 Required The #include directive shall be followed by either a or "filename" sequence Rule 20.4 Required A macro shall not be defined with the same name as a keyword Rule 20.5 Advisory #undef should not be used Rule 20.7 Required Expressions resulting from the expansion of macro parameters shall be enclosed in parentheses Rule 20.8 Required The controlling expression of a #if or #elif preprocessing directive shall evaluate to 0 or 1 Rule 20.9 Required All identifiers used in the controlling expression of #if or #elif preprocessing directives shall be #define’d before evaluation Rule 20.10 Advisory The # and ## preprocessor operators should not be used Rule 20.11 Required A macro parameter immediately following a # operator shall not immediately be followed by a ## operator Rule 20.12 Required A macro parameter used as an operand to the # or ## operators, which is itself subject to further macro replacement, shall only be used as an operand to these operators Rule 20.13 Required A line whose first token is # shall be a valid preprocessing directive Rule 20.14 Required All #else, #elif and #endif preprocessor directives shall reside in the same file as the #if, #ifdef or #ifndef directive to which they are related Rule 21.1 Required #define and #undef shall not be used on a reserved identifier or reserved macro name Rule 21.2 Required A reserved identifier or macro name shall not be declared Rule 21.3 Required The memory allocation and deallocation functions of shall not be used Rule 21.4 Required The standard header file shall not be used Rule 21.5 Required The standard header file shall not be used Rule 21.6 Required The Standard Library input/output functions shall not be used Rule 21.7 Required The atof, atoi, atol and atoll functions of shall not be used Rule 21.8 Required The library functions abort, exit, getenv and system of shall not be used Rule 21.9 Required The library functions bsearch and qsort of shall not be used Rule 21.10 Required The Standard Library time and date functions shall not be used Rule 21.11 Required The standard header file shall not be used Rule 21.12 Advisory The exception handling features of should not be used Rule 22.1 Required All resources obtained dynamically by means of Standard Library functions shall be explicitly released Rule 22.2 Mandatory A block of memory shall only be freed if it was allocated by means of a Standard Library function Rule 22.3 Required The same file shall not be open for read and write access at the same time on different streams Rule 22.4 Mandatory There shall be no attempt to write to a stream which has been opened as read-only Rule 22.5 Mandatory A pointer to a FILE object shall not be dereferenced Rule 22.6 Mandatory The value of a pointer to a FILE shall not be used after the associated stream has been closed