LANG.STRUCT.LOOP.UB : Potential Unbounded Loop

Summary

A loop does not have a fixed bound. (For more information, see the notes below.)

Properties

WARNING_FILTER += allow class="Potential Unbounded Loop"

Example

#include <stdlib.h>

void lang_struct_loop_ub (void){
    int i = 0;
    while (rand()) { /* 'Potential Unbounded Loop' warning issued here */
      if (i++ == 10) {break;}
    }
}

Notes

CodeSonar will issue an Unbounded Loop warning if it cannot identify a loop counter whose value is updated and tested in a way that guarantees that the loop will executed a bounded number of times. This means that the following must all hold.

• The loop counter is a variable.
• The loop condition compares the loop counter against a constant value, using <, <=,>, or >=.
• The loop updates the value of the loop counter in a direction consistent with the comparison in the loop condition. If the loop condition compares the loop counter against an upper bound, the loop body should increment the counter; if the condition tests it against a lower bound, the loop body should decrement it.
• In for loops, the loop counter is only updated in the update (third) expression in the for header - not in the loop body.

Variables whose value is tested in the loop condition with one of {<, <=,>, >=} are called candidate loop counters. If there are one or more candidate loop counters but none of them satisfies all the required conditions, CodeSonar will report each candidate considered along with the reason that it is not suitable for demonstrating boundedness.

Use the NON_TERMINATING_LOOP_MARK configuration file parameter to specify loops that should not trigger a Potential Unbounded Loop warning. For example, this can be useful if you use constructs like for(;;){...} and while(1){...} and wish to continue to do so, or if you wish to be able to add special code comments to identify loops to exclude from this check.

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
• CPU_SPEED_ADJUSTMENT
• DIV_BY_ZERO_CRASHES
• DIV_OVERFLOW_CRASHES
• 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
• NON_TERMINATING_LOOP_MARK
• NULL_POINTER_DEREF_CRASHES
• NULL_SENTINEL_CHAR_SIZE
• PARAMETER_EVALUATION_ORDER
• REACHABILITY_ROOTS
• REPORT_SIMILAR_WARNINGS
• ROLLBACK_SUMMARIES_ON_ABORT
• SEARCH_BOUND
• SEARCH_BOUND_NOISE_THRESHOLD
• SYSTEM_INCLUDE_PATHS
• TIME_LIMIT_INTRA_EXPLORE
• UNINITIALIZED_GLOBALS
• VOLATILE_TREATMENT
• WARNING_FILTER