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The assert() statement is a convenient mechanism for incorporating diagnostic tests in code. Expressions used with the standard assert statement should not contain side effects. Typically, the The behavior of the assert statement depends on the status of a runtime property. If When enabled, the assert statement is designed to evaluate evaluates its expression argument and throw throws an AssertionError if the result of the expression is convertible to false. If When disabled, assert is defined to be a no-operation. Consequently, op; any side effects resulting from evaluation of the expression in the assertion are lost in production quality code. Consequently, expressions used with the standard assert statement must not produce side effects.

Noncompliant Code Example

This noncompliant code example demonstrates an action being carried out in an assertion. The idea is attempts to delete all the null names from the list in an assertion. However, however, the boolean Boolean expression is unexpectedly not evaluated when assertions are disabled.

Code Block

bgColor	#ffcccc

private ArrayList<String> names;

void process(int index) {
  assert names.remove(null); // sideSide effect 
  // ...
}

Compliant Solution

Avoid the The possibility of side effects in assertions . This can be achieved avoided by decoupling the boolean Boolean expression from the assertion.:

Code Block

bgColor	#ccccff

private ArrayList<String> names;

void process(int index) {
  boolean nullsRemoved = names.remove(null);
  assert nullsRemoved; // noNo side effect 
  // ... 
}

Risk Assessment

Side effects in assertions can lead to unexpected and erroneous behaviorresult in program behavior that depends on whether assertions are enabled or disabled.

Rule	Severity	Likelihood	Remediation Cost	Priority	Level

EXP31

EXP06-J

low

Low

unlikely

Unlikely

low

Low

P3

L3

Related Vulnerabilities

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

Other Languages

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Automated Detection

Automated detection of assertion operands that contain locally visible side effects is straightforward. Some analyses could require programmer assistance to determine which method invocations lack side effects.

Tool

Version

Checker

Description

CodeSonar

Include Page

	CodeSonar_V
	CodeSonar_V

JAVA.STRUCT.SE.ASSERT

Assertion Contains Side Effects (Java)

PVS-Studio

Include Page

	PVS-Studio_V
	PVS-Studio_V

V6055

SonarQube

Include Page

	SonarQube_V
	SonarQube_V

S3346

Expressions used in "assert" should not produce side effects

Related Guidelines

SEI CERT C Coding Standard

PRE31

...

-C. Avoid side effects in

...

arguments to unsafe macros

Android Implementation Details

The assert statement is supported on the Dalvik VM but is ignored under the default configuration. Assertions may be enabled by setting the system property debug.assert via: adb shell setprop debug.assert 1 or by sending the command-line argument --enable-assert to the Dalvik VM.