Some functions return a pointer to an object that cannot be modified without causing undefined behavior. These functions include getenv(), setlocale(), localeconv(), asctime(), and strerror(). In such cases, the function call results must be treated as being const-qualified.
The C Standard, 7.2224.4.6, paragraph 4 [ISO/IEC 9899:20112024], defines getenv() as follows:
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If the string returned by getenv() must be altered, a local copy should be created. Altering the string returned by getenv() is undefined behavior. (see See undefined behavior 184.).
Similarly, subclause 7.11.1.1, paragraph 8 [ISO/IEC 9899:20112024], defines setlocale() as follows:
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And subclause 7.11.2.1, paragraph 8 [ISO/IEC 9899:20112024], defines localeconv() as follows:
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Altering the string returned by setlocale() or the structure returned by localeconv() are undefined behaviors. (see See undefined behaviors 120 and 121.) . Furthermore, the C Standard imposes no requirements on the contents of the string by setlocale(). Consequently, no assumptions can be made as to the string's internal contents or structure.
Finally, subclause 7.2426.6.23, paragraph 4 4 [ISO/IEC 9899:20112024], states:
The The
strerrorfunction returns a pointer to the string, the contents of which are locale-specific. The array pointed to shall not be modified by the program, but may be overwritten by . The behavior is undefined if the returned value is used after a subsequent call to thestrerrorfunctionthestrerrorfunction, or after the thread which called the function to obtain the returned value has exited.
Altering the string returned by strerror() is undefined behavior. (see See undefined behavior 184.).
Noncompliant Code Example (getenv())
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Modifying the object pointed to by the return value of getenv(), setlocale(), localeconv(), asctime(), or strerror() is undefined behavior. Even if the modification succeeds, the modified object can be overwritten by a subsequent call to the same function.
Rule | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
ENV30-C | Low | Probable | Medium | P4 | L3 |
Automated Detection
Tool | Version | Checker | Description | ||||||
|---|---|---|---|---|---|---|---|---|---|
| Astrée |
| stdlib-const-pointer-assign | Partially checked | ||||||
| Axivion Bauhaus Suite |
| CertC-ENV30 | |||||||
| CodeSonar |
| BADFUNC.GETENV | Use of getenv | ||||||
| Compass/ROSE |
Can detect violations of this rule. In particular, it ensures that the result of | |||||||||
| Cppcheck Premium |
| premium-cert-env30-c | Fully implemented | ||||||
| Helix QAC |
| C1492, C1493, C1494 DF4751, DF4752, DF4753 | |||||||
| Klocwork |
| MISRA.STDLIB.CTYPE.RANGE.2012_AMD1 | |||||||
| LDRA tool suite |
| 107 D | Partially Implemented | ||||||
| Parasoft C/C++test |
| CERT_C-ENV30-a | The pointers returned by the Standard Library functions 'localeconv', 'getenv', 'setlocale' or, 'strerror' shall only be used as if they have pointer to const-qualified type | ||||||
| Polyspace Bug Finder |
| Checks for modification of internal buffer returned from nonreentrant standard function (rule fully covered) | |||||||
| PVS-Studio |
| V675 | |||||||
| RuleChecker |
| stdlib-const-pointer-assign | Partially checked |
Related Vulnerabilities
Search for vulnerabilities resulting from the violation of this rule on the CERT website.
Related Guidelines
Key here (explains table format and definitions)
Taxonomy | Taxonomy item | Relationship |
|---|---|---|
| ISO/IEC TS 17961:2013 | Modifying the string returned by getenv, localeconv, setlocale, and strerror [libmod] | Prior to 2018-01-12: CERT: Unspecified Relationship |
Bibliography
| [IEEE Std 1003.1:2013] | XSH, System Interfaces, getenvXSH, System Interfaces, setlocaleXSH, System Interfaces, localeconv |
| [ISO/IEC 9899: |
| 2024] | 7.11.1.1, "The setlocale Function"7.11.2.1, "The localeconv Function"7. |
24.4.6, "The getenv Function"7. |
| 26.6. |
3, "The strerror Function" |
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