PRE04-C. Do not reuse a standard header file name

If a file with the same name as a standard header is placed in the search path for included source files, the behavior is undefined.

The following table lists these standard headers:

`<assert.h>`	`<complex.h>`	`<ctype.h>`	`<errno.h>`	`<fenv.h>`
`<float.h>`	`<inttypes.h>`	`<iso646.h>`	`<limits.h>`	`<locale.h>`
`<math.h>`	`<setjmp.h>`	`<signal.h>`	`<stdarg.h>`	`<stdbool.h>`
`<stddef.h>`	`<stdint.h>`	`<stdio.h>`	`<stdlib.h>`	`<string.h>`
`<tgmath.h>`	`<time.h>`	`<uchar.h>`	`<wchar.h>`	`<wctype.h>`

Do not reuse standard header file names, system-specific header file names, or other header file names.

Noncompliant Code Example

In this noncompliant code example, the programmer chooses to use a local version of the standard library but does not make the change clear.

#include "stdio.h"  /* confusing, distinct from <stdio.h> */

/* ... */

Compliant Solution

The solution addresses the problem by giving the local library a unique name (per recommendation PRE08-C. Guarantee that header file names are unique), which makes it apparent that the library used is not the original.

/* Using a local version of stdio.h */ 
#include "mystdio.h"

/* ... */

Risk Assessment

Using header file names that conflict with other header file names can result in an incorrect file being included.

Recommendation	Severity	Likelihood	Remediation Cost	Priority	Level
PRE04-C	low	unlikely	medium	P2	L3

Automated Detection

Tool	Version	Checker	Description
LDRA tool suite	9.7.1

Related Vulnerabilities

Search for vulnerabilities resulting from the violation of this rule on the CERT website.

Related Guidelines

CERT C++ Secure Coding Standard: PRE04-CPP. Do not reuse a standard header file name

ISO/IEC 9899:1999 Section 7.1.2, "Standard Headers"

Bibliography

PRE03-C. Prefer typedefs to defines for encoding types 01. Preprocessor (PRE)

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