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The C Standard identifies five distinct situations in which undefined behavior (UB) may arise as a result of invoking a function using a declaration that is incompatible with its definition or by supplying incorrect types or numbers of arguments:

Functions that are appropriately declared (as in DCL40-C. Do not create incompatible declarations of the same function or object) will typically generate a compiler diagnostic message if they are supplied with the wrong number or types of arguments. However, there are cases in which supplying the incorrect arguments to a function will, at best, generate compiler warnings. Although such warnings should be resolved, they do not prevent program compilation. (See MSC00-C. Compile cleanly at high warning levels.)

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The header <tgmath.h> provides type-generic macros for math functions. Although most functions from the <math.h> header have a complex counterpart in <complex.h>, several functions do not. Calling any of the following type-generic functions with complex values results in is undefined behavior.

Functions That Should Not Be Called with Complex Values

This noncompliant code example attempts to take the base-2 logarithm of a complex number, resulting in undefined behavior:

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If the clog2() function is not available for an implementation as an extension, the programmeng programmer can take the base-2 logarithm of a complex number, using log() instead of log2(), because log() can be used on complex arguments, as shown in this compliant solution:

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In this noncompliant example, the C standard library function strchr() is called through the function pointer fp declared with a prototype with incorrectly typed arguments. According to the C Standard, 6.3.2.3, paragraph 8 [ISO/IEC 9899:20112024],

A pointer to a function of one type may be converted to a pointer to a function of another type and back again; the result shall compare equal to the original pointer. If a converted pointer is used to call a function whose type is not compatible with the referenced the referenced type, the behavior is undefined.

See undefined behavior 26.

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The open() function accepts a third argument to determine a newly created file's access mode. If open() is used to create a new file , and the third argument is omitted, the file may be created with unintended access permissions. (see See FIO06-C. Create files with appropriate access permissions.).

In this noncompliant code example from a vulnerability in the useradd() function of the shadow-utils package CVE-2006-1174, the third argument to open() is accidentally omitted:

fd = open(ms, O_CREAT | O_EXCL | O_WRONLY | O_TRUNC);

Note thatTechnically, technically, it is also incorrect to pass a third argument to open() when not creating a new file (that is, with the O_CREAT flag not set).

Compliant Solution (POSIX)

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Calling a function with incorrect arguments can result in unexpected or unintended program behavior.

Automated Detection

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)

CERT-CWE Mapping Notes

Key here for mapping notes

CWE-685 and EXP37-C

EXP37-C = Union( CWE-685, CWE-686) Intersection( CWE-685, CWE-686) = Ø

CWE-686 and EXP37-C

Intersection( EXP37-C, FIO47-C) =

• Invalid argument types passed to format I/O function

EXP37-C – FIO47-C =

• Invalid argument types passed to non-format I/O function

FIO47-C – EXP37-C =

• Invalid format string, but correctly matches arguments in number and type

EXP37-C = Union( CWE-685, CWE-686

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)

Intersection( CWE-685, CWE-686) = Ø

CWE-628 and EXP37-C

CWE-628 = Union( EXP37-C, list) where list =

• Improper ordering of function arguments (that does not violate argument types)

• Wrong argument values or references

Bibliography

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