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Java: Option to detach from the JVM in the thread destructor.

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This commit is contained in:
Joachim Kuebart 2021-08-13 17:26:57 +02:00
commit b58c554cde
2 changed files with 37 additions and 1 deletions
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10
CHANGES.current
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@ -7,6 +7,16 @@ the issue number to the end of the URL: https://github.com/swig/swig/issues/
Version 4.1.0 (in progress)
===========================
2022-05-23: jkuebart
[Java] On some versions of Android, specifically Android 6,
detaching the current thread from the JVM after every invocation
causes a memory leak.
Offer SWIG_JAVA_DETACH_ON_THREAD_END to configure a behaviour
where the JVM is only detached in the thread destructor.
See https://developer.android.com/training/articles/perf-jni#threads.
2022-05-15: erezgeva, eiselekd
[Lua, Perl, Octave, PHP, Tcl] #2275 #2276 #2283 Add argcargv.i library containing
(int ARGC, char **ARGV) multi-argument typemaps.

28
Lib/java/director.swg
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@ -51,6 +51,22 @@ SWIGINTERN int Swig::GetThreadName(char *name, size_t len) {
#endif
#if defined(SWIG_JAVA_DETACH_ON_THREAD_END)
#include <pthread.h>
namespace {
void detach(void* jvm) {
static_cast<JavaVM*>(jvm)->DetachCurrentThread();
}
pthread_key_t detachKey;
void makeDetachKey() {
pthread_key_create(&detachKey, detach);
}
}
#endif
namespace Swig {
/* Java object wrapper */
@ -201,9 +217,19 @@ namespace Swig {
#else
director_->swig_jvm_->AttachCurrentThread(jenv, &args);
#endif
#if defined(SWIG_JAVA_DETACH_ON_THREAD_END)
// At least on Android 6, detaching after every call causes a memory leak.
// Instead, register a thread desructor and detach only when the thread ends.
// See https://developer.android.com/training/articles/perf-jni#threads
static pthread_once_t once = PTHREAD_ONCE_INIT;
pthread_once(&once, makeDetachKey);
pthread_setspecific(detachKey, director->swig_jvm_);
#endif
}
~JNIEnvWrapper() {
#if !defined(SWIG_JAVA_NO_DETACH_CURRENT_THREAD)
#if !defined(SWIG_JAVA_DETACH_ON_THREAD_END) && !defined(SWIG_JAVA_NO_DETACH_CURRENT_THREAD)
// Some JVMs, eg jdk-1.4.2 and lower on Solaris have a bug and crash with the DetachCurrentThread call.
// However, without this call, the JVM hangs on exit when the thread was not created by the JVM and creates a memory leak.
if (env_status == JNI_EDETACHED)