FULL PRODUCT VERSION :
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)
FULL OS VERSION :
OS X Yosemite 10.10.5
A DESCRIPTION OF THE PROBLEM :
While debugging a JVMTI agent (whose code I unfortunately cannot share with you at the moment), I discovered that GetLocalInstance behaves different than documented.
The documentation [1] states that it returns JVMTI_ERROR_INVALID_SLOT "if the specified frame is a static method frame."
When the specified frame referred to a method "public static void method(int i)", however, I have observed a return value of JVMTI_ERROR_TYPE_MISMATCH.
Moreover, if the method was "public static void method(Object o)" instead, with an Object in the first slot, I even got JVMTI_ERROR_NONE, with the Object o as receiving instance.
Cursory inspection of VM_GetOrSetLocal::check_slot_type (src/share/vm/prims/jvmtiImpl.cpp) suggest that this method, which produces the error code returned by GetLocalInstance, is indeed oblivious as to whether the receiver (which a static method doesn't have) or the object in slot 0 is requested; this would explain the behavior described above.
I hope this is enough information to reproduce the error.
[1] <http://docs.oracle.com/javase/8/docs/platform/jvmti/jvmti.html#GetLocalInstance>
THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: Yes
THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: Yes
STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
- Call a native method from within a static method of signature (of varying signature, see "expected and actual results").
- Let the native method attempt to use JVMTI's GetLocalInstance function to access the receiver of the stack method.
- Observe the error code.
EXPECTED VERSUS ACTUAL BEHAVIOR :
static void method(int i):
expected: JVMTI_ERROR_INVALID_SLOT
actual: JVMTI_ERROR_TYPE_MISMATCH
static void method(Object o):
expected: JVMTI_ERROR_INVALID_SLOT
actual: JVMTI_ERROR_NONE
static void method():
expected: JVMTI_ERROR_INVALID_SLOT
actual: JVMTI_ERROR_INVALID_SLOT
REPRODUCIBILITY :
This bug can be reproduced always.
CUSTOMER SUBMITTED WORKAROUND :
Detect whether the method is static (using GetFrameLocation + GetMethodModifiers) before calling GetLocalInstance.
Just treating VMTI_ERROR_TYPE_MISMATCH as VMTI_ERROR_INVALID_SLOT unfortunately doesn't work, as the static method's first argument may be an Object, in which case *no* error would be return, even though it should.
java version "1.8.0_111"
Java(TM) SE Runtime Environment (build 1.8.0_111-b14)
Java HotSpot(TM) 64-Bit Server VM (build 25.111-b14, mixed mode)
FULL OS VERSION :
OS X Yosemite 10.10.5
A DESCRIPTION OF THE PROBLEM :
While debugging a JVMTI agent (whose code I unfortunately cannot share with you at the moment), I discovered that GetLocalInstance behaves different than documented.
The documentation [1] states that it returns JVMTI_ERROR_INVALID_SLOT "if the specified frame is a static method frame."
When the specified frame referred to a method "public static void method(int i)", however, I have observed a return value of JVMTI_ERROR_TYPE_MISMATCH.
Moreover, if the method was "public static void method(Object o)" instead, with an Object in the first slot, I even got JVMTI_ERROR_NONE, with the Object o as receiving instance.
Cursory inspection of VM_GetOrSetLocal::check_slot_type (src/share/vm/prims/jvmtiImpl.cpp) suggest that this method, which produces the error code returned by GetLocalInstance, is indeed oblivious as to whether the receiver (which a static method doesn't have) or the object in slot 0 is requested; this would explain the behavior described above.
I hope this is enough information to reproduce the error.
[1] <http://docs.oracle.com/javase/8/docs/platform/jvmti/jvmti.html#GetLocalInstance>
THE PROBLEM WAS REPRODUCIBLE WITH -Xint FLAG: Yes
THE PROBLEM WAS REPRODUCIBLE WITH -server FLAG: Yes
STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
- Call a native method from within a static method of signature (of varying signature, see "expected and actual results").
- Let the native method attempt to use JVMTI's GetLocalInstance function to access the receiver of the stack method.
- Observe the error code.
EXPECTED VERSUS ACTUAL BEHAVIOR :
static void method(int i):
expected: JVMTI_ERROR_INVALID_SLOT
actual: JVMTI_ERROR_TYPE_MISMATCH
static void method(Object o):
expected: JVMTI_ERROR_INVALID_SLOT
actual: JVMTI_ERROR_NONE
static void method():
expected: JVMTI_ERROR_INVALID_SLOT
actual: JVMTI_ERROR_INVALID_SLOT
REPRODUCIBILITY :
This bug can be reproduced always.
CUSTOMER SUBMITTED WORKAROUND :
Detect whether the method is static (using GetFrameLocation + GetMethodModifiers) before calling GetLocalInstance.
Just treating VMTI_ERROR_TYPE_MISMATCH as VMTI_ERROR_INVALID_SLOT unfortunately doesn't work, as the static method's first argument may be an Object, in which case *no* error would be return, even though it should.
- relates to
-
JDK-8080406 VM_GetOrSetLocal doesn't check local slot type against requested type
-
- Resolved
-