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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 9899:2011],
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 type, the behavior is undefined.
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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:
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