16f6c0aecf
Inline adoc files when they are included exactly once. Also fix language tags because this inlining gives us better information on what language the code is written in.
89 lines
2.2 KiB
Plaintext
89 lines
2.2 KiB
Plaintext
== Why is this an issue?
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Double-checked locking can be used for lazy initialization of ``++volatile++`` fields, but only if field assignment is the last step in the ``++synchronized++`` block. Otherwise you run the risk of threads accessing a half-initialized object.
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=== Noncompliant code example
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[source,java]
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----
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public class MyClass {
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private volatile List<String> strings;
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public List<String> getStrings() {
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if (strings == null) { // check#1
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synchronized(MyClass.class) {
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if (strings == null) {
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strings = new ArrayList<>(); // Noncompliant
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strings.add("Hello"); //When threadA gets here, threadB can skip the synchronized block because check#1 is false
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strings.add("World");
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}
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}
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}
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return strings;
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}
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}
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----
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=== Compliant solution
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[source,java]
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----
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public class MyClass {
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private volatile List<String> strings;
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public List<String> getStrings() {
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if (strings == null) { // check#1
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synchronized(MyClass.class) {
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if (strings == null) {
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List<String> tmpList = new ArrayList<>();
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tmpList.add("Hello");
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tmpList.add("World");
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strings = tmpList;
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}
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}
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}
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return strings;
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}
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}
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----
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== Resources
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* https://wiki.sei.cmu.edu/confluence/x/6zdGBQ[CERT, LCK10-J.] - Use a correct form of the double-checked locking idiom
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=== Related rules
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* S2168 - Double-checked locking should not be used
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ifdef::env-github,rspecator-view[]
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'''
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== Implementation Specification
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(visible only on this page)
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=== Message
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Fully initialize this new "xxx" before assigning it to the field.
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'''
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== Comments And Links
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(visible only on this page)
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=== on 15 Jun 2015, 18:07:41 Ann Campbell wrote:
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\[~tamas.vajk] I've targeted this to C# because I think it might be relevant.
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=== on 17 Aug 2015, 06:56:13 Tamas Vajk wrote:
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\[~ann.campbell.2] This seems very specific (to Java), I wouldn't target C#. There might be minor differences in the Java and C# memory model when using ``++volatile++``, which I'm not aware of.
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=== on 17 Aug 2015, 16:08:28 Ann Campbell wrote:
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Thanks for the review [~tamas.vajk]. Un-targeted.
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endif::env-github,rspecator-view[]
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