LANG.FUNCS.IRV : Ignored Return Value

Summary

The value returned by some function has not been used.

Properties

WARNING_FILTER += discard class="Ignored Return Value"

Example

#include <stdio.h>

int lang_funcs_irv(FILE *f){
  feof(f);               /* 'Ignored Return Value' warning issued here
                          * - factory settings include
                          *   RETURN_CHECKER_BUILT_IN_CHECKED_PURE_FUNCS += ^feof$
                          */
  /* ... remainder of function (for example, operations on f) */
  return 0;
}

Enforced and Excluded Checks

For all procedures, CodeSonar uses a statistical analysis to determine whether the return value can be ignored. The sensitivity of this analysis is controlled by the RETURN_CHECKER_RATIO and RETURN_CHECKER_CONFIDENCE parameters.

• To enforce return value use for a specific procedure or set of procedures (overruling the statistical analysis if necessary), use one of the following, as appropriate.
  • RETURN_CHECKER_CHECKED_FUNCS for functions with side effects whose return values must be checked on all paths.
  • RETURN_CHECKER_CHECKED_PURE_FUNCS for side-effect-free functions whose return values must be checked on at least one path.
  • RETURN_CHECKER_CHECKED_PURE_SOME_PATHS_FUNCS for side-effect-free functions whose return values must be checked on all paths.
• To exclude a specific procedure or set of procedures from the return value use check (overruling the statistical analysis if necessary), use the RETURN_CHECKER_IGNORED_FUNCS configuration file parameter. RETURN_CHECKER_IGNORED_FUNCS takes precedence over the parameters that enforce checking.

  If you want to suppress warnings for some function fname() that is specified in factory settings for RETURN_CHECKER_BUILT_IN_CHECKED_FUNCS or RETURN_CHECKER_BUILT_IN_CHECKED_PURE_FUNCS while still preserving those factory settings in your configuration file, add the following rule to your configuration file.

  RETURN_CHECKER_IGNORED_FUNCS+= ^fname$
  

The general template configuration file contains factory settings enforcing checks for many functions with important return values, and permitting return values to be ignored for several more. For full lists, see the "Factory Settings" in the documentation for each parameter.

• RETURN_CHECKER_BUILT_IN_CHECKED_FUNCS
• RETURN_CHECKER_BUILT_IN_CHECKED_PURE_FUNCS
• RETURN_CHECKER_IGNORED_FUNCS

Effects on warning instance scores

For warnings issued due to ignoring the return value of a function specified by one of the parameters that enforce checking, the warning instance score will depend in part on which parameter was used. All else being equal, the ordering is:

• RETURN_CHECKER_CHECKED_FUNCS (highest score)
• RETURN_CHECKER_CHECKED_PURE_FUNCS, RETURN_CHECKER_CHECKED_PURE_SOME_PATHS_FUNCS (if checked on no paths)
• RETURN_CHECKER_CHECKED_PURE_SOME_PATHS_FUNCS (if checked on some but not all paths)
• RETURN_CHECKER_BUILT_IN_CHECKED_FUNCS
• RETURN_CHECKER_BUILT_IN_CHECKED_PURE_FUNCS
• not specified with any of these parameters: statistical inference only (lowest score)

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.

• ASSUME_FUNCPTR_PARAMETERS_MAYBE_FREED
• ASSUME_FUNCPTR_PARAMETERS_MAYBE_INITIALIZED
• ASSUME_FUNCPTR_PARAMETERS_MAYBE_MODIFIED
• ASSUME_OTHER_PARAMETERS_MAYBE_FREED
• ASSUME_OTHER_PARAMETERS_MAYBE_INITIALIZED
• ASSUME_OTHER_PARAMETERS_MAYBE_MODIFIED
• ASSUME_UNDEFINED_PARAMETERS_MAYBE_FREED
• ASSUME_UNDEFINED_PARAMETERS_MAYBE_INITIALIZED
• ASSUME_UNDEFINED_PARAMETERS_MAYBE_MODIFIED
• ASSUME_VARARG_PARAMETERS_MAYBE_FREED
• ASSUME_VARARG_PARAMETERS_MAYBE_INITIALIZED
• ASSUME_VARARG_PARAMETERS_MAYBE_MODIFIED
• CALL_SITE_EXPANSIONS
• CALL_SITE_EXPANSION_BOUND
• CPU_SPEED_ADJUSTMENT
• DIV_BY_ZERO_CRASHES
• DIV_OVERFLOW_CRASHES
• DP_REFINEMENT_APPROXIMATE
• DP_REFINEMENT_APPROXIMATE_DISMISS
• DP_REFINEMENT_APPROXIMATE_DISMISS_TIMEOUT
• DP_REFINEMENT_APPROXIMATE_TIMEOUT
• DP_REFINEMENT_EXACT
• DP_REFINEMENT_EXACT_DISMISS
• DP_REFINEMENT_EXACT_DISMISS_TIMEOUT
• DP_REFINEMENT_EXACT_TIMEOUT
• EXPLORE_MORE_LOOP_PATHS
• EXPLORE_SELF_ASSIGNMENT
• FLOAT_IS_ADVERSARIAL
• FUNCTION_MAP
• FUNCTION_POINTER_RESOLUTION
• IGNORE_CPP_CODE
• IMPLICIT_INITIALIZER_ELT_LIMIT
• INFER_CONST
• LOOP_COUNTER_DISTRUST
• MAX_ALLOCATION_SIZE
• MAX_CLOBBERED_FIELDS
• MAX_COPIED_FIELDS
• MAX_EXPRESSION_COMPLEXITY
• MAX_MODIFIED_VALUES
• MAX_PERCENT_F_CHARACTERS
• MAX_PERCENT_LF_CHARACTERS
• MAX_POINTER_ANALYSIS_PASSES
• MAX_SUMMARIES_PER_PROCEDURE
• NULL_POINTER_DEREF_CRASHES
• NULL_SENTINEL_CHAR_SIZE
• PARAMETER_EVALUATION_ORDER
• REACHABILITY_ROOTS
• REPORT_SIMILAR_WARNINGS
• RETURN_CHECKER_BUILT_IN_CHECKED_FUNCS
• RETURN_CHECKER_BUILT_IN_CHECKED_PURE_FUNCS
• RETURN_CHECKER_CHECKED_FUNCS
• RETURN_CHECKER_CHECKED_PURE_FUNCS
• RETURN_CHECKER_CHECKED_PURE_SOME_PATHS_FUNCS
• RETURN_CHECKER_CONFIDENCE
• RETURN_CHECKER_DISCARD_CONFIDENCE
• RETURN_CHECKER_IGNORED_FUNCS
• RETURN_CHECKER_RATIO
• ROLLBACK_SUMMARIES_ON_ABORT
• SEARCH_BOUND
• SEARCH_BOUND_NOISE_THRESHOLD
• SYSTEM_INCLUDE_PATHS
• TIME_LIMIT_INTRA_EXPLORE
• UNINITIALIZED_GLOBALS
• VOLATILE_TREATMENT
• WARNING_FILTER