...
Although it advises against depending on parentheses for specifying evaluation order, guideline "EXP08-J. Do not write more than once to the same variable within an expression" applies only to expressions that contain side effects.
Noncompliant Code Example
The intent of the expression in this noncompliant code example is to add the variable OFFSET to the result of the bitwise logical AND between x and MASK.
...
| Code Block |
|---|
x & (1337 - 1337) |
Compliant Solution
This compliant solution uses parentheses to ensure that the expression evaluates as intended.
| Code Block | ||
|---|---|---|
| ||
public static final int MASK = 1337;
public static final int OFFSET = -1337;
public static int computeCode(int x) {
return (x & MASK) + OFFSET;
}
|
Exceptions
EXP06-EX0: Parentheses may be omitted from mathematical expressions that follow the algebraic precedence rules. For instance, consider the expression:
...
| Code Block | ||
|---|---|---|
| ||
x + (y * z) |
Risk Assessment
Mistakes regarding precedence guidelines can cause an expression to be evaluated in an unintended way. This can lead to unexpected and abnormal program behavior.
Guideline | Severity | Likelihood | Remediation Cost | Priority | Level |
|---|---|---|---|---|---|
EXP06-J | low | probable | medium | P4 | L3 |
Automated Detection
Detection of all expressions using low-precedence operators without parentheses is straightforward. Determining the correctness of such uses is infeasible in the general case; heuristic warnings could be useful.
Related Guidelines
C Coding Standard: "EXP00-C. Use parentheses for precedence of operation"
C++ Secure Coding Standard: "EXP00-CPP. Use parentheses for precedence of operation"
Bibliography
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="8e176a52d127659f-f4b0e348-47b04c2a-b2acb103-c1d22c55f2b3cec47740f1a1"><ac:plain-text-body><![CDATA[ | [[ESA 2005 | AA. Bibliography#ESA 05]] | Rule 65: Use parentheses to explicitly indicate the order of execution of numerical operators | ]]></ac:plain-text-body></ac:structured-macro> | |
<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="ea5433a0bd986eda-2202d69c-4c3041b4-af0bb5b1-826c4ee3bd5162e0ba8536f3"><ac:plain-text-body><![CDATA[ | [[Tutorials 2008 | AA. Bibliography#Tutorials 08]] | [Expressions, Statements, and Blocks | http://java.sun.com/docs/books/tutorial/java/nutsandbolts/expressions.html] | ]]></ac:plain-text-body></ac:structured-macro> |
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<ac:structured-macro ac:name="unmigrated-wiki-markup" ac:schema-version="1" ac:macro-id="ae51522c72a0e631-a8a23bee-47f240e0-b684ac2e-faf5cae0375ad93ac71f5354"><ac:plain-text-body><![CDATA[ | [[Rogue 2000 | AA. Bibliography#Rogue 2000]] | Rule 77: Clarify the order of operations with parentheses | ]]></ac:plain-text-body></ac:structured-macro> |
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EXP05EXP04-J. Use braces for the body of an if, for, or while statementDo not perform assignments in conditional statements 02. Expressions (EXP) EXP07-J. Understand the differences between bitwise and logical operators