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Useless include

An include directive is present but not used

Since R2022b

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Description

This defect occurs when you do not use an included header.

For instance, when you do not:

  • Invoke macros defined in the included file or the included file's includes.

  • Use data types defined in the included file or the included file's includes.

  • Call or use references to an object or function defined in the included file or the included file's includes.

  • Use an externally visible object provided by the included file outside of the file.

If an object is used inside a nested macro, Polyspace can miss the usage. As a result, Polyspace might flag the include that declares the object as USELESS_INCLUDE.

Risk

Unnecessary file dependencies slow the build speed of the project. To improve build speed, remove include directives that are not used.

Fix

Remove the unused include directive.

Examples

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This example does not use the <cmath> and <stdexcedpt> header files or their include directives. 

#include <iostream>      
#include <cmath>        
#include <stdexcept>    
#include <vector>       

int age = 0;
std::vector<int> allAges;

void saveAge()
{
	std::cout << "Enter age: ";
	std::cin >> age;
	
	allAges.push_back(age);
}

int main() {
	while (age <= 40)
	{
		saveAge();
	}

	for (int x : allAges)
	{
		std::cout << x << std::endl;
	}

	return 0;
}
Correction — Remove Unused Include Directives

One correction is to delete the unused include directives from the file.

#include <iostream>
#include <vector>

int age = 0;
std::vector<int> allAges;

void saveAge()
{
	std::cout << "Enter age: ";
	std::cin >> age;
	
	allAges.push_back(age);
}

int main() {
	while (age <= 40)
	{
		saveAge();
	}

	for (int x : allAges)
	{
		std::cout << x << std::endl;
	}

	return 0;
}

Result Information

Group: Good Practice
Language: C | C++
Default: Off
Command-Line Syntax: USELESS_INCLUDE
Impact: Low

Version History

Introduced in R2022b

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See Also