Incorrect Use of Autoboxing and Unboxing for Performance Critical Operations

Incomplete Base

Structure: Simple

Description

The code uses boxed primitives, which may introduce inefficiencies into performance-critical operations.

Extended Description

Languages such as Java and C# support automatic conversion through their respective compilers from primitive types into objects of the corresponding wrapper classes, and vice versa. For example, a compiler might convert an int to Integer (called autoboxing) or an Integer to int (called unboxing). This eliminates forcing the programmer to perform these conversions manually, which makes the code cleaner. However, this feature comes at a cost of performance and can lead to resource exhaustion and impact availability when used with generic collections. Therefore, they should not be used for scientific computing or other performance critical operations. They are only suited to support "impedance mismatch" between reference types and primitives.

Common Consequences 1

Scope: Availability

Impact: DoS: Resource Consumption (CPU)DoS: Resource Consumption (Memory)DoS: Resource Consumption (Other)Reduce Performance

Incorrect autoboxing/unboxing would result in reduced performance, which sometimes can lead to resource consumption issues.

Potential Mitigations 1

Phase: Implementation

Use of boxed primitives should be limited to certain situations such as when calling methods with typed parameters. Examine the use of boxed primitives prior to use. Use SparseArrays or ArrayMap instead of HashMap to avoid performance overhead.

Demonstrative Examples 2

Java has a boxed primitive for each primitive type. A long can be represented with the boxed primitive Long. Issues arise where boxed primitives are used when not strictly necessary.

Code Example:Bad
Java
java

In the above loop, we see that the count variable is declared as a boxed primitive. This causes autoboxing on the line that increments. This causes execution to be magnitudes less performant (time and possibly space) than if the "long" primitive was used to declare the count variable, which can impact availability of a resource.

This code uses primitive long which fixes the issue.

Code Example:Good
Java
java

References 2

Oracle Java Documentation

https://docs.oracle.com/javase/1.5.0/docs/guide/language/autoboxing.html

ID: REF-1051

SEI CERT Oracle Coding Standard for Java : Rule 02. Expressions (EXP)

The Software Engineering Institute

https://wiki.sei.cmu.edu/confluence/display/java/EXP04-J.+Do+not+pass+arguments+to+certain+Java+Collections+Framework+methods+that+are+a+different+type+than+the+collection+parameter+type

ID: REF-1052

Applicable Platforms

Languages:

Java : UndeterminedC# : Undetermined

Technologies:

Not Technology-Specific : Undetermined

Modes of Introduction

Implementation

Related Weaknesses

ChildOf:

Uncontrolled Resource Consumption (CWE-400)

Taxonomy Mapping

SEI CERT Oracle Coding Standard for Java
ISA/IEC 62443