EXP31-J. Avoid side effects in assertions

The assert() statement is a convenient mechanism for incorporating diagnostic tests in code. Expressions used with the standard assert statement should not have side effects. Typically, the behavior of the assert statement depends on the status of a runtime property. If defined, the assert statement is defined to evaluate its expression argument and abort if the result of the expression is convertible to false. If undefined, assertis defined to be a no-op. Consequently, any side effects resulting from evaluation of the expression in the assertion are lost in non-debugging versions of the code.

Noncompliant Code Example

This noncompliant code example demonstrates an action being carried out in an assertion. The idea is to delete all the null names from the list, however, the boolean expression is not evaluated.

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

Compliant Solution

Avoid the possibility of side effects in assertions. This can be achived by decoupling the boolean from the assertion.

void process(int index) {
  boolean nullsRemoved = names.remove(null);
  assert nullsRemoved; /* no side effect */
  /* ... */
}

Risk Assessment

Side effects in assertions can lead to unexpected and erroneous behavior.

Related Vulnerabilities

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

Other Languages

This rule appears in the C Coding Standard as EXP31-C. Avoid side effects in assertions.

This rule appears in the C++ Coding Standard as EXP31-CPP. Avoid side effects in assertions.

References

[Tutorials 08] Programming With Assertions