AUTOSAR C++14 Rule A18-0-2

The error state of a conversion from string to a numeric value shall be checked

Description

Rule Definition

The error state of a conversion from string to a numeric value shall be checked.

Rationale

Converting strings to a numeric value might result in error conditions, for instance, when the input string:

• Does not contain a number

• Contains a number, but is out of range

• Contains additional data after a number

If you use C standard library functions such as atoi(), the preceding input errors might result in undefined behavior. To avoid undefined behavior and undetected errors, check the error state of output when converting strings to a numeric value. Avoid using C standard library function. Use C++ standard library functions, such as std::stoi(), std::stof(), and std::stol() instead.

Polyspace Implementation

Polyspace^® flags the C standard library string-to-number functions of atoi(), atol(), and atof().

Troubleshooting

If you expect a rule violation but Polyspace does not report it, see Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

Use C++ Library Functions for Converting Strings to Numeric Value

#include <cstdlib> 
#include <iostream> 
#include <string> 

void foo() { 
	std::string str1 = "7"; 
	std::string str2 = "3.1415"; 
	std::string str3 = "three"; 

	int myint1 = std::stoi(str1); //Compliant 
	float myint2 = std::stof(str2); //Compliant 
	long myint3 = std::stol(str3); //Compliant 

	const char* str4 = "12"; 
	const char* str5 = "2.7182"; 
	const char* str6 = "undefinedError"; 

	int num4 = atoi(str4); //Noncompliant 
	float num5 = atof(str5); //Noncompliant 
	long num6 = atol(str6); //Noncompliant  
	//...
} 

In this example, Polyspace flags the use of C standard library functions for converting strings to numeric value. For instance:

• The string-to-number functions from the C standard library, such as atoi(), atof(), and atol() are noncompliant flagged because an invalid conversion results in undefined behavior.

• The string-to-number functions from the C++ standard library std::stoi(), std::stof(), and std::stol() are not flagged because an invalid conversion produces a std::invalid_argument exception, which is defined behavior.

Check Information

Group: Language Support Library

Category: Required, Automated

Version History

Introduced in R2019a