Thread local variable causes JVM crash through JNI

Question

Hi All,
My team developed a JDBC driver which uses some native C codes. (Compiler: cl.exe, O/S: Windows XP)
I found that JVM crashes at specific point. So I used debugger(Visual Studio 2005) to find the position.
==================File1.c=====================
JNIEXPORT jbyteArray JNICALL
Java_com_lone_wolf_MyClass_myFunc(
JNIEnv *env, jclass cls,
jint msgtype, jbyteArray recvarr)
jbyteArray outarr;
int x = 3;
outarr = my_initializer (int &x);
return outarr;
==================File2.c=====================
__declspec(thread) int thread_id;
static jbyteArray my_initializer (int *a)
thread_id = *a; // HERE JVM CRASHES
When my_initializer() tries to put *a into thread_id, JVM crashed with the following error message.
# An unexpected error has been detected by HotSpot Virtual Machine:
# EXCEPTION_ACCESS_VIOLATION (0xc0000005) at pc=0x4931c6bf, pid=3560, tid=848
# Java VM: Java HotSpot(TM) Client VM (1.5.0_01-b08 mixed mode)
# Problematic frame:
# C [hello.dll+0xc6bf]
--------------- T H R E A D ---------------
Current thread (0x00037168): JavaThread "main" [_thread_in_native, id=848]
Stack: [0x00040000,0x00080000), sp=0x0007f494, free space=253k
Native frames: (J=compiled Java code, j=interpreted, Vv=VM code, C=native code)
C [hello.dll+0xc6bf]
C [hello.dll+0xbebb]
C [hello.dll+0x3c30]
C [hello.dll+0x18e6]
C [hello.dll+0x11b8]
j com.lone.wolf.MyClass.myFunc(I[B)[B+0
v ~StubRoutines::call_stub
V [jvm.dll+0x8176e]
V [jvm.dll+0xd481d]
V [jvm.dll+0x8163f]
V [jvm.dll+0x885cd]
C [java.exe+0x14c0]
C [java.exe+0x64cd]
C [kernel32.dll+0x16ff7]
VM Arguments:
jvm_args: -Xms128m -Xmx1024m
java_command: sampler.Sampler
--------------- S Y S T E M ---------------
OS: Windows XP Build 2600 Service Pack 2
CPU:total 4 family 6, cmov, cx8, fxsr, mmx, sse, sse2, ht
Memory: 4k page, physical 2062180k(1378880k free), swap 4003992k(3252828k free)
vm_info: Java HotSpot(TM) Client VM (1.5.0_01-b08) for windows-x86, built on Dec 6 2004 19:51:00 by "java_re" with MS VC++ 6.0
Any idea how to solve this issue will be greatly appreciated.
Thank you.

Answer 1

This deffinition ( __declspec(thread) ) of the thread local veriable does not works in some cases (see articles in MSDN how to define thread local variables in C++ code). JVM loads your native module (DLL) with LoadLibrary function. This is one of the cases when __declspec(thread) is wrong in C++ code.