Avoid in-band error indicators while designing interfaces. This practice is commonly used by C library functions but is not recommended. One example from the C Standard of a troublesome in-band error indicator is EOF. (See void FIO34-C. Use int to capture the return value of character IO functions that might be used to check for end of file and void FIO35-C. Use feof() and ferror() to detect end-of-file and file errors when sizeof(int) == sizeof(char).) Distinguish between characters read from a file and EOF or WEOF). Another problematic use of in-band error indicators from the C Standard involving the size_t and time_t types is described by VOID MSC31by
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- integer conversions do not result in lost or misinterpreted data
- FLP07-C. Cast the return value of a function that returns a floating-point type
- INT18-C. Evaluate integer expressions in a larger size before comparing or assigning to that size
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Noncompliant Code Example (sprintf())
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