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ISO/IEC TS 17961 [chrsgnext]

Passing arguments to character handling functions that are not representable as unsigned char

Description

Rule Definition

Passing arguments to character handling functions that are not representable as unsigned char.1

Polyspace Implementation

This checker checks for Invalid use of standard library integer routine.

Examples

expand all

Issue

Invalid use of standard library integer routine occurs when you use invalid arguments with an integer function from the standard library. This defect picks up:

  • Character Conversion

    toupper, tolower

  • Character Checks

    isalnum, isalpha, iscntrl, isdigit, isgraph, islower, isprint, ispunct, isspace, isupper, isxdigit

  • Integer Division

    div, ldiv

  • Absolute Values

    abs, labs

Fix

The fix depends on the root cause of the defect. Often the result details show a sequence of events that led to the defect. You can implement the fix on any event in the sequence. If the result details do not show the event history, you can trace back using right-click options in the source code and see previous related events. See also Interpret Bug Finder Results in Polyspace Desktop User Interface.

See examples of fixes below.

If you do not want to fix the issue, add comments to your result or code to avoid another review. See:

Example - Absolute Value of Large Negative
#include <limits.h>
#include <stdlib.h>

int absoluteValue(void) {

    int neg = INT_MIN;
    return abs(neg);
}

The input value to abs is INT_MIN. The absolute value of INT_MIN is INT_MAX+1. This number cannot be represented by the type int.

Correction — Change Input Argument

One possible correction is to change the input value to fit returned data type. In this example, change the input value to INT_MIN+1.

#include <limits.h>
#include <stdlib.h>

int absoluteValue(void) {

    int neg = INT_MIN+1;
    return abs(neg);
}

Check Information

Decidability: Undecidable

Version History

Introduced in R2019a


1 Extracts from the standard "ISO/IEC TS 17961 Technical Specification - 2013-11-15" are reproduced with the agreement of AFNOR. Only the original and complete text of the standard, as published by AFNOR Editions - accessible via the website www.boutique.afnor.org - has normative value.