CERT C: Rec. PRE04-C

Do not reuse a standard header file name

Since R2025a

Description

Rule Definition

Do not reuse a standard header file name.¹

Polyspace Implementation

This checker checks for Standard header file name reused.

Examples

Standard header file name reused

Issue

The issue occurs when you include a user-defined header file that has the same name as one of the standard library header files listed in this table.

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

Polyspace reports a violation for header files that are enclosed in quotes ("") when those header files reuse the name of one of the files in the preceding table.

Risk

If the search path for included source files has a file with the same name as one of the standard library header files, the behavior is undefined.

Fix

Do not reuse the file names of the standard library headers when including a user-defined header.

Example — Reuse of a Standard Header File Name

#include <stdio.h>
#include "math.h" // Noncompliant

double area(double radius)
{
  double pi = MY_PI; // custom MY_PI macro defined in math.h

  return pi * radius * radius;
}

In this example, Polyspace flags the inclusion of "math.h" because it reuses the name of a standard library header.

Correction — Use Unique Name for User-Defined Header

#include <stdio.h>
#include "custom_math.h" // Compliant

double area(double radius)
{
  double pi = MY_PI; // custom MY_PI macro defined in custom_math.h

  return pi * radius * radius;
}

One possible correction is to use a distinctive name for user-defined header files, such as custom_math.h.

Check Information

Group: Rec. 01. Preprocessor (PRE)

Version History

Introduced in R2025a