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Avoid possible GC issues in Java example code

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This prevents the previously-set element value from being collected
before or during the call to setElement. Since C++ could still have
a reference to during that time, it could lead to misbehavior.
This commit is contained in:
Jesse Rusak 2017-08-29 11:00:23 -04:00
commit 175ab4e720
1 changed files with 6 additions and 11 deletions
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17
Doc/Manual/Java.html
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@ -8165,13 +8165,10 @@ public class Container {
// Ensure that the GC doesn't collect any Element set from Java
// as the underlying C++ class stores a shallow copy
private Element elementReference;
private long getCPtrAndAddReference(Element element) {
elementReference = element;
return Element.getCPtr(element);
}
public void setElement(Element e) {
exampleJNI.Container_setElement(swigCPtr, this, getCPtrAndAddReference(e), e);
exampleJNI.Container_setElement(swigCPtr, this, Element.getCPtr(e), e);
elementReference = e;
}
}
</pre>
@ -8179,22 +8176,20 @@ public class Container {
<p>
The following typemaps will generate the desired code.
The 'javain' typemap matches the input parameter type for the <tt>setElement</tt> method.
The 'javain' typemap matches the input parameter type for the <tt>setElement</tt> method and allows adding code after the call.
The 'javacode' typemap simply adds in the specified code into the Java proxy class.
</p>
<div class="code">
<pre>
%typemap(javain) Element *e "getCPtrAndAddReference($javainput)"
%typemap(javain,
post="elementReference = $javainput;\n"
) Element *e "Element.getCPtr($javainput)"
%typemap(javacode) Container %{
// Ensure that the GC doesn't collect any element set from Java
// as the underlying C++ class stores a shallow copy
private Element elementReference;
private long getCPtrAndAddReference(Element element) {
elementReference = element;
return Element.getCPtr(element);
}
%}
</pre>
</div>