SEI CERT C Coding Standard

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changes.mady.by.user Aaron Ballman

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According to the C Standard, subclause 7.4 [ISO/IEC 9899:2011],

The header <ctype.h> declares several functions useful for classifying and mapping characters. In all cases the argument is an int, the value of which shall be representable as an unsigned char or shall equal the value of the macro EOF. If the argument has any other value, the behavior is undefined.

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isalnum()

isalpha()

isascii()XSI

isblank()

iscntrl()

isdigit()

isgraph()

islower()

isprint()

ispunct()

isspace()

isupper()

isxdigit()

toascii()XSI

toupper()

tolower()

Note: XSI denotes an X/Open System Interfaces Extension to ISO/IEC 9945—POSIX. The functions are not defined by the C Standard.

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Code Block
bgColor#FFcccc
langc
#include <ctype.h>
#include <stddef.h>
 
ptrdiff_t count_preceding_whitespace(const char *s) {
  const char *t = s;

  /* possiblyPossibly *t < 0 */
  while (*t && isspace(*t)) {
    ++t;
  }
  return t - s;
}

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Rule

Severity

Likelihood

Remediation Cost

Priority

Level

STR37-C

lowLow

unlikelyUnlikely

lowLow

P3

L3

Automated Detection

Tool

Version

Checker

Description

Compass/ROSE

  

Could detect violations of this rule by seeing if the argument to a character - handling function (listed above) is not an unsigned char

ECLAIR

Include Page
ECLAIR_V
ECLAIR_V

CC2.STR37

Fully implemented

PRQA QA-C
Include Page
PRQA_V
PRQA_V
Special case of STR34-CFully implemented

Related Vulnerabilities

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CERT C Secure Coding StandardSTR34-C. Cast characters to unsigned char before converting to larger integer sizes
CERT C++ Secure Coding StandardSTR37-CPP. Arguments to character handling functions must be representable as an unsigned char
ISO/IEC TS 17961 (Draft)Passing arguments to character-handling functions that are not representable as unsigned char [chrsgnext]
MITRE CWECWE-704, Incorrect type conversion or cast
CWE-686, Function call with incorrect argument type

Bibliography

[ISO/IEC 9899:2011]Subclause 7.4, "Character Handling <ctype.h>"
[Kettlewell 2002]Section 1.1, "<ctype.h> and Characters Types"

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