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https://issues.apache.org/jira/browse/GROOVY-10918?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17689340#comment-17689340
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Eric Milles commented on GROOVY-10918:
--------------------------------------
Given your example:
{code:groovy}
@groovy.transform.CompileStatic // line 1
String test(String s) {
s = s.chars().mapToObj{"X"}.collect(Collectors.joining())
println s.charAt(0)
s = s.chars().mapToObj{"Y"}.collect(Collectors.joining())
println s.charAt(0)
s = s.chars().mapToObj{"Z"}.collect(Collectors.joining())
println s.charAt(0)
return s
}
{code}
The bytecode for the method looks like this:
{code}
public java.lang.String test(java.lang.String s);
0 aload_1 [s]
1 invokevirtual java.lang.String.chars() : java.util.stream.IntStream
[92]
4 new Scratch$_test_closure1 [94]
7 dup
8 aload_0 [this]
9 aload_0 [this]
10 invokespecial Scratch$_test_closure1(java.lang.Object,
java.lang.Object) [97]
13 invokedynamic 2 cast(groovy.lang.Closure) :
java.util.function.IntFunction [100]
18 invokeinterface
java.util.stream.IntStream.mapToObj(java.util.function.IntFunction) :
java.util.stream.Stream [106] [nargs: 2]
23 invokestatic java.util.stream.Collectors.joining() :
java.util.stream.Collector [112]
26 invokeinterface
java.util.stream.Stream.collect(java.util.stream.Collector) : java.lang.Object
[118] [nargs: 2]
31 astore_2
32 aload_2
33 invokedynamic 2 cast(java.lang.Object) : java.lang.String [61]
38 astore_1 [s]
39 aload_2
40 pop
41 aload_0 [this]
42 aload_1 [s]
43 iconst_0
44 invokevirtual java.lang.String.charAt(int) : char [122]
47 invokestatic java.lang.Character.valueOf(char) : java.lang.Character
[128]
50 invokevirtual Scratch.println(java.lang.Object) : void [131]
53 aconst_null
54 pop
55 aload_1 [s]
56 invokevirtual java.lang.String.chars() : java.util.stream.IntStream
[92]
59 new Scratch$_test_closure2 [133]
62 dup
63 aload_0 [this]
64 aload_0 [this]
65 invokespecial Scratch$_test_closure2(java.lang.Object,
java.lang.Object) [134]
68 invokedynamic 2 cast(groovy.lang.Closure) :
java.util.function.IntFunction [100]
73 invokeinterface
java.util.stream.IntStream.mapToObj(java.util.function.IntFunction) :
java.util.stream.Stream [106] [nargs: 2]
78 invokestatic java.util.stream.Collectors.joining() :
java.util.stream.Collector [112]
81 invokeinterface
java.util.stream.Stream.collect(java.util.stream.Collector) : java.lang.Object
[118] [nargs: 2]
86 astore_3
87 aload_3
88 invokedynamic 2 cast(java.lang.Object) : java.lang.String [61]
93 astore_1 [s]
94 aload_3
95 pop
96 aload_0 [this]
97 aload_1 [s]
98 iconst_0
99 invokevirtual java.lang.String.charAt(int) : char [122]
102 invokestatic java.lang.Character.valueOf(char) : java.lang.Character
[128]
105 invokevirtual Scratch.println(java.lang.Object) : void [131]
108 aconst_null
109 pop
110 aload_1 [s]
111 invokevirtual java.lang.String.chars() : java.util.stream.IntStream
[92]
114 new Scratch$_test_closure3 [136]
117 dup
118 aload_0 [this]
119 aload_0 [this]
120 invokespecial Scratch$_test_closure3(java.lang.Object,
java.lang.Object) [137]
123 invokedynamic 2 cast(groovy.lang.Closure) :
java.util.function.IntFunction [100]
128 invokeinterface
java.util.stream.IntStream.mapToObj(java.util.function.IntFunction) :
java.util.stream.Stream [106] [nargs: 2]
133 invokestatic java.util.stream.Collectors.joining() :
java.util.stream.Collector [112]
136 invokeinterface
java.util.stream.Stream.collect(java.util.stream.Collector) : java.lang.Object
[118] [nargs: 2]
141 astore 4
143 aload 4
145 invokedynamic 2 cast(java.lang.Object) : java.lang.String [61]
150 astore_1 [s]
151 aload 4
153 pop
154 aload_0 [this]
155 aload_1 [s]
156 iconst_0
157 invokevirtual java.lang.String.charAt(int) : char [122]
160 invokestatic java.lang.Character.valueOf(char) : java.lang.Character
[128]
163 invokevirtual Scratch.println(java.lang.Object) : void [131]
166 aconst_null
167 pop
168 aload_1 [s]
169 areturn
Line numbers:
[pc: 0, line: 3]
[pc: 41, line: 4]
[pc: 55, line: 5]
[pc: 96, line: 6]
[pc: 110, line: 7]
[pc: 154, line: 8]
[pc: 168, line: 9]
Local variable table:
[pc: 0, pc: 170] local: this index: 0 type: Scratch
[pc: 0, pc: 170] local: s index: 1 type: java.lang.String
{code}
So it appears to be using local variable slots 2, 3 and 4 to save intermediate
results before assigning back to "s" (slot 1).
> Memory leak: local variable values are not discarded
> ----------------------------------------------------
>
> Key: GROOVY-10918
> URL: https://issues.apache.org/jira/browse/GROOVY-10918
> Project: Groovy
> Issue Type: Bug
> Components: groovy-runtime
> Affects Versions: 4.0.9
> Reporter: Andriy Rysin
> Priority: Major
> Labels: MemoryLeak
> Attachments: TestOOM.groovy, TestOOMIcj.java, TestOOMJ.java,
> TestOOM_works.groovy, groovy_oom.png
>
>
> When I run the code below with 3 statements with closures inside the method
> the local var (parameter) values (all 4 of them) are staying in memory.
> I don't see the same problem if I run corresponding Java code with lambdas.
> Run TestOOM.groovy with
> -Xmx600M -XX:+HeapDumpOnOutOfMemoryError
> Notice groovy fails:
> Y
> Z
> java.lang.OutOfMemoryError: Java heap space
> Dumping heap to java_pid147612.hprof ...
> Heap dump file created [497819587 bytes in 0.136 secs]
> Caught: java.lang.OutOfMemoryError: Java heap space
> java.lang.OutOfMemoryError: Java heap space
> at test.TestOOM.test(TestOOM.groovy:31)
> at test.TestOOM.run(TestOOM.groovy:41)
> But Java version does not.
> It looks like all the values of s are still in memory (see screenshot), even
> though previous values should be discarded.
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