RFR (XS) 8189766: whitebox failure with -Xcheck:jni

[Lois Foltan]

Looks good.
Lois

On 5/29/2018 3:06 AM, David Holmes wrote:
> bug: https://bugs.openjdk.java.net/browse/JDK-8189766
> webrev: http://cr.openjdk.java.net/~dholmes/8189766/webrev/
>
> A WB_ENTRY already handles the pending JNI exception check by 
> explicitly clearing it via a helper:
>
> #define WB_ENTRY(result_type, header) JNI_ENTRY(result_type, header) \
>   ClearPendingJniExcCheck _clearCheck(env);
>
> #define WB_END JNI_END
>
> But the whitebox function then does e.g:
>
> WB_ENTRY(jobject, WB_GetBooleanVMFlag(JNIEnv* env, jobject o, jstring 
> name))
>   bool result;
>   if (GetVMFlag <bool> (thread, env, name, &result, &JVMFlag::boolAt)) {
>     ThreadToNativeFromVM ttnfv(thread); // can't be in VM when we call 
> JNI
>     return booleanBox(thread, env, result);
>   }
>   return NULL;
> WB_END
>
> where booleanBox is defined eventually as:
>
> template <typename T>
> static jobject box(JavaThread* thread, JNIEnv* env, Symbol* name, 
> Symbol* sig, T value) {
>   ResourceMark rm(thread);
>   jclass clazz = env->FindClass(name->as_C_string());
>   CHECK_JNI_EXCEPTION_(env, NULL);
>   jmethodID methodID = env->GetStaticMethodID(clazz,
>         vmSymbols::valueOf_name()->as_C_string(),
>         sig->as_C_string());
>   CHECK_JNI_EXCEPTION_(env, NULL);
>   jobject result = env->CallStaticObjectMethod(clazz, methodID, value);
>   CHECK_JNI_EXCEPTION_(env, NULL);
>   return result;
> }
>
> so we call JNI methods that will set the pending_jni_exception_check 
> flag, but CHECK_JNI_EXCEPTION is defined as:
>
> #define CHECK_JNI_EXCEPTION_(env, value) \
>   do { \
>     JavaThread* THREAD = JavaThread::thread_from_jni_environment(env); \
>     if (HAS_PENDING_EXCEPTION) { \
>       return(value); \
>     } \
>   } while (0)
>
> which means it is not clearing the pending_jni_exception_check flag 
> even though it is checking for exceptions!
>
> So we explicitly clear the flag. Trying to use the JNI 
> ExceptionOccurred function fails as not all the methods that call 
> CHECK_JNI_EXCEPTION are _thread_in_native.
>
> Testing (in progress):
>          hotspot tier1 and tier2 with -Xcheck:jni
>          regular CI testing
>
> Thanks,
> David