HDFS-11529. Add libHDFS API to return last exception. Contributed by Sailesh Mukil.

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs-tests/expect.h

@@ -163,6 +163,24 @@ struct hdfsFile_internal;
     ret = -errno; \
     } while (ret == -EINTR);
 
+#define EXPECT_STR_CONTAINS(str, substr) \
+    do { \
+        char *_my_ret_ = (str); \
+        int _my_errno_ = errno; \
+        if ((str) == NULL) { \
+            fprintf(stderr, "TEST_ERROR: failed on %s:%d with NULL return " \
+              "return value (errno: %d): expected substring: %s\n", \
+              __FILE__, __LINE__, _my_errno_, (substr)); \
+            return -1; \
+        } \
+        if (strstr((str), (substr)) == NULL) { \
+            fprintf(stderr, "TEST_ERROR: failed on %s:%d with return " \
+              "value %s (errno: %d): expected substring: %s\n", \
+              __FILE__, __LINE__, _my_ret_, _my_errno_, (substr)); \
+            return -1; \
+        } \
+    } while (0);
+
 /**
  * Test that an HDFS file has the given statistics.
  *

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs-tests/test_libhdfs_threaded.c

@@ -165,6 +165,12 @@ static int doTestHdfsOperations(struct tlhThreadInfo *ti, hdfsFS fs,
     /* There should not be any file to open for reading. */
     EXPECT_NULL(hdfsOpenFile(fs, paths->file1, O_RDONLY, 0, 0, 0));
 
+    /* Check if the exceptions are stored in the TLS */
+    EXPECT_STR_CONTAINS(hdfsGetLastExceptionRootCause(),
+                        "File does not exist");
+    EXPECT_STR_CONTAINS(hdfsGetLastExceptionStackTrace(),
+                        "java.io.FileNotFoundException");
+
     /* hdfsOpenFile should not accept mode = 3 */
     EXPECT_NULL(hdfsOpenFile(fs, paths->file1, 3, 0, 0, 0));
 

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/exception.c

@@ -110,15 +110,50 @@ void getExceptionInfo(const char *excName, int noPrintFlags,
     }
 }
 
+/**
+ * getExceptionUtilString: A helper function that calls 'methodName' in
+ * ExceptionUtils. The function 'methodName' should have a return type of a
+ * java String.
+ *
+ * @param env        The JNI environment.
+ * @param exc        The exception to get information for.
+ * @param methodName The method of ExceptionUtils to call that has a String
+ *                    return type.
+ *
+ * @return           A C-type string containing the string returned by
+ *                   ExceptionUtils.'methodName', or NULL on failure.
+ */
+static char* getExceptionUtilString(JNIEnv *env, jthrowable exc, char *methodName)
+{
+    jthrowable jthr;
+    jvalue jVal;
+    jstring jStr = NULL;
+    char *excString = NULL;
+    jthr = invokeMethod(env, &jVal, STATIC, NULL,
+        "org/apache/commons/lang/exception/ExceptionUtils",
+        methodName, "(Ljava/lang/Throwable;)Ljava/lang/String;", exc);
+    if (jthr) {
+        destroyLocalReference(env, jthr);
+        return NULL;
+    }
+    jStr = jVal.l;
+    jthr = newCStr(env, jStr, &excString);
+    if (jthr) {
+        destroyLocalReference(env, jthr);
+        return NULL;
+    }
+    destroyLocalReference(env, jStr);
+    return excString;
+}
+
 int printExceptionAndFreeV(JNIEnv *env, jthrowable exc, int noPrintFlags,
         const char *fmt, va_list ap)
 {
     int i, noPrint, excErrno;
     char *className = NULL;
-    jstring jStr = NULL;
-    jvalue jVal;
     jthrowable jthr;
     const char *stackTrace;
+    const char *rootCause;
 
     jthr = classNameOfObject(exc, env, &className);
     if (jthr) {
@@ -139,32 +174,30 @@ int printExceptionAndFreeV(JNIEnv *env, jthrowable exc, int noPrintFlags,
         noPrint = 0;
         excErrno = EINTERNAL;
     }
+
+    // We don't want to use ExceptionDescribe here, because that requires a
+    // pending exception. Instead, use ExceptionUtils.
+    rootCause = getExceptionUtilString(env, exc, "getRootCauseMessage");
+    stackTrace = getExceptionUtilString(env, exc, "getStackTrace");
+    // Save the exception details in the thread-local state.
+    setTLSExceptionStrings(rootCause, stackTrace);
+
     if (!noPrint) {
         vfprintf(stderr, fmt, ap);
         fprintf(stderr, " error:\n");
 
-        // We don't want to  use ExceptionDescribe here, because that requires a
-        // pending exception.  Instead, use ExceptionUtils.
-        jthr = invokeMethod(env, &jVal, STATIC, NULL, 
-            "org/apache/commons/lang/exception/ExceptionUtils",
-            "getStackTrace", "(Ljava/lang/Throwable;)Ljava/lang/String;", exc);
-        if (jthr) {
-            fprintf(stderr, "(unable to get stack trace for %s exception: "
-                    "ExceptionUtils::getStackTrace error.)\n", className);
-            destroyLocalReference(env, jthr);
+        if (!rootCause) {
+            fprintf(stderr, "(unable to get root cause for %s)\n", className);
+        } else {
+            fprintf(stderr, "%s", rootCause);
+        }
+        if (!stackTrace) {
+            fprintf(stderr, "(unable to get stack trace for %s)\n", className);
         } else {
-            jStr = jVal.l;
-            stackTrace = (*env)->GetStringUTFChars(env, jStr, NULL);
-            if (!stackTrace) {
-                fprintf(stderr, "(unable to get stack trace for %s exception: "
-                        "GetStringUTFChars error.)\n", className);
-            } else {
-                fprintf(stderr, "%s", stackTrace);
-                (*env)->ReleaseStringUTFChars(env, jStr, stackTrace);
-            }
+            fprintf(stderr, "%s", stackTrace);
         }
     }
-    destroyLocalReference(env, jStr);
+
     destroyLocalReference(env, exc);
     free(className);
     return excErrno;

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/exception.h

@@ -29,9 +29,14 @@
  *
  * If you encounter an exception, return a local reference to it.  The caller is
  * responsible for freeing the local reference, by calling a function like
- * PrintExceptionAndFree.  (You can also free exceptions directly by calling
+ * printExceptionAndFree. (You can also free exceptions directly by calling
  * DeleteLocalRef.  However, that would not produce an error message, so it's
  * usually not what you want.)
+ *
+ * The root cause and stack trace exception strings retrieved from the last
+ * exception that happened on a thread are stored in the corresponding
+ * thread local state and are accessed by hdfsGetLastExceptionRootCause and
+ * hdfsGetLastExceptionStackTrace respectively.
  */
 
 #include "platform.h"
@@ -81,7 +86,8 @@ void getExceptionInfo(const char *excName, int noPrintFlags,
                       int *excErrno, int *shouldPrint);
 
 /**
- * Print out information about an exception and free it.
+ * Store the information about an exception in the thread-local state and print
+ * it and free the jthrowable object.
  *
  * @param env             The JNI environment
  * @param exc             The exception to print and free
@@ -97,7 +103,8 @@ int printExceptionAndFreeV(JNIEnv *env, jthrowable exc, int noPrintFlags,
         const char *fmt, va_list ap);
 
 /**
- * Print out information about an exception and free it.
+ * Store the information about an exception in the thread-local state and print
+ * it and free the jthrowable object.
  *
  * @param env             The JNI environment
  * @param exc             The exception to print and free
@@ -113,7 +120,8 @@ int printExceptionAndFree(JNIEnv *env, jthrowable exc, int noPrintFlags,
         const char *fmt, ...) TYPE_CHECKED_PRINTF_FORMAT(4, 5);
 
 /**
- * Print out information about the pending exception and free it.
+ * Store the information about the pending exception in the thread-local state
+ * and print it and free the jthrowable object.
  *
  * @param env             The JNI environment
  * @param noPrintFlags    Flags which determine which exceptions we should NOT

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/hdfs.c

@@ -2956,6 +2956,7 @@ done:
     destroyLocalReference(env, jFileBlockHosts);
     destroyLocalReference(env, jHost);
     if (ret) {
+        errno = ret;
         if (blockHosts) {
             hdfsFreeHosts(blockHosts);
         }
@@ -3512,7 +3513,15 @@ int hdfsFileIsEncrypted(hdfsFileInfo *fileInfo)
     return !!(extInfo->flags & HDFS_EXTENDED_FILE_INFO_ENCRYPTED);
 }
 
+char* hdfsGetLastExceptionRootCause()
+{
+  return getLastTLSExceptionRootCause();
+}
 
+char* hdfsGetLastExceptionStackTrace()
+{
+  return getLastTLSExceptionStackTrace();
+}
 
 /**
  * vim: ts=4: sw=4: et:

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/include/hdfs/hdfs.h

@@ -1042,6 +1042,38 @@ extern  "C" {
     LIBHDFS_EXTERNAL
     void hadoopRzBufferFree(hdfsFile file, struct hadoopRzBuffer *buffer);
 
+    /**
+     * Get the last exception root cause that happened in the context of the
+     * current thread, i.e. the thread that called into libHDFS.
+     *
+     * The pointer returned by this function is guaranteed to be valid until
+     * the next call into libHDFS by the current thread.
+     * Users of this function should not free the pointer.
+     *
+     * A NULL will be returned if no exception information could be retrieved
+     * for the previous call.
+     *
+     * @return           The root cause as a C-string.
+     */
+    LIBHDFS_EXTERNAL
+    char* hdfsGetLastExceptionRootCause();
+
+    /**
+     * Get the last exception stack trace that happened in the context of the
+     * current thread, i.e. the thread that called into libHDFS.
+     *
+     * The pointer returned by this function is guaranteed to be valid until
+     * the next call into libHDFS by the current thread.
+     * Users of this function should not free the pointer.
+     *
+     * A NULL will be returned if no exception information could be retrieved
+     * for the previous call.
+     *
+     * @return           The stack trace as a C-string.
+     */
+    LIBHDFS_EXTERNAL
+    char* hdfsGetLastExceptionStackTrace();
+
 #ifdef __cplusplus
 }
 #endif

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/jni_helper.c

@@ -498,29 +498,98 @@ static JNIEnv* getGlobalJNIEnv(void)
  */
 JNIEnv* getJNIEnv(void)
 {
-    JNIEnv *env;
-    THREAD_LOCAL_STORAGE_GET_QUICK();
+    struct ThreadLocalState *state = NULL;
+    THREAD_LOCAL_STORAGE_GET_QUICK(&state);
+    if (state) return state->env;
+
     mutexLock(&jvmMutex);
-    if (threadLocalStorageGet(&env)) {
+    if (threadLocalStorageGet(&state)) {
       mutexUnlock(&jvmMutex);
       return NULL;
     }
-    if (env) {
+    if (state) {
       mutexUnlock(&jvmMutex);
-      return env;
+
+      // Free any stale exception strings.
+      free(state->lastExceptionRootCause);
+      free(state->lastExceptionStackTrace);
+      state->lastExceptionRootCause = NULL;
+      state->lastExceptionStackTrace = NULL;
+
+      return state->env;
     }
 
-    env = getGlobalJNIEnv();
-    mutexUnlock(&jvmMutex);
-    if (!env) {
-      fprintf(stderr, "getJNIEnv: getGlobalJNIEnv failed\n");
+    /* Create a ThreadLocalState for this thread */
+    state = threadLocalStorageCreate();
+    if (!state) {
+      fprintf(stderr, "getJNIEnv: Unable to create ThreadLocalState\n");
       return NULL;
     }
-    if (threadLocalStorageSet(env)) {
-      return NULL;
+    state->env = getGlobalJNIEnv();
+    mutexUnlock(&jvmMutex);
+    if (!state->env) {
+      goto fail;
     }
-    THREAD_LOCAL_STORAGE_SET_QUICK(env);
-    return env;
+    if (threadLocalStorageSet(state)) {
+      goto fail;
+    }
+    THREAD_LOCAL_STORAGE_SET_QUICK(state);
+
+    return state->env;
+
+fail:
+    fprintf(stderr, "getJNIEnv: getGlobalJNIEnv failed\n");
+    hdfsThreadDestructor(state);
+    return NULL;
+}
+
+char* getLastTLSExceptionRootCause()
+{
+    struct ThreadLocalState *state = NULL;
+    THREAD_LOCAL_STORAGE_GET_QUICK(&state);
+    if (!state) {
+        mutexLock(&jvmMutex);
+        if (threadLocalStorageGet(&state)) {
+            mutexUnlock(&jvmMutex);
+            return NULL;
+        }
+        mutexUnlock(&jvmMutex);
+    }
+    return state->lastExceptionRootCause;
+}
+
+char* getLastTLSExceptionStackTrace()
+{
+    struct ThreadLocalState *state = NULL;
+    THREAD_LOCAL_STORAGE_GET_QUICK(&state);
+    if (!state) {
+        mutexLock(&jvmMutex);
+        if (threadLocalStorageGet(&state)) {
+            mutexUnlock(&jvmMutex);
+            return NULL;
+        }
+        mutexUnlock(&jvmMutex);
+    }
+    return state->lastExceptionStackTrace;
+}
+
+void setTLSExceptionStrings(const char *rootCause, const char *stackTrace)
+{
+    struct ThreadLocalState *state = NULL;
+    THREAD_LOCAL_STORAGE_GET_QUICK(&state);
+    if (!state) {
+        mutexLock(&jvmMutex);
+        if (threadLocalStorageGet(&state)) {
+            mutexUnlock(&jvmMutex);
+            return;
+        }
+        mutexUnlock(&jvmMutex);
+    }
+
+    free(state->lastExceptionRootCause);
+    free(state->lastExceptionStackTrace);
+    state->lastExceptionRootCause = (char*)rootCause;
+    state->lastExceptionStackTrace = (char*)stackTrace;
 }
 
 int javaObjectIsOfClass(JNIEnv *env, jobject obj, const char *name)

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/jni_helper.h

@@ -105,6 +105,8 @@ jthrowable globalClassReference(const char *className, JNIEnv *env, jclass *out)
 jthrowable classNameOfObject(jobject jobj, JNIEnv *env, char **name);
 
 /** getJNIEnv: A helper function to get the JNIEnv* for the given thread.
+ * It gets this from the ThreadLocalState if it exists. If a ThreadLocalState
+ * does not exist, one will be created.
  * If no JVM exists, then one will be created. JVM command line arguments
  * are obtained from the LIBHDFS_OPTS environment variable.
  * @param: None.
@@ -112,6 +114,39 @@ jthrowable classNameOfObject(jobject jobj, JNIEnv *env, char **name);
  * */
 JNIEnv* getJNIEnv(void);
 
+/**
+ * Get the last exception root cause that happened in the context of the
+ * current thread.
+ *
+ * The pointer returned by this function is guaranteed to be valid until
+ * the next call to invokeMethod() by the current thread.
+ * Users of this function should not free the pointer.
+ *
+ * @return The root cause as a C-string.
+ */
+char* getLastTLSExceptionRootCause();
+
+/**
+ * Get the last exception stack trace that happened in the context of the
+ * current thread.
+ *
+ * The pointer returned by this function is guaranteed to be valid until
+ * the next call to invokeMethod() by the current thread.
+ * Users of this function should not free the pointer.
+ *
+ * @return The stack trace as a C-string.
+ */
+char* getLastTLSExceptionStackTrace();
+
+/** setTLSExceptionStrings: Sets the 'rootCause' and 'stackTrace' in the
+ * ThreadLocalState if one exists for the current thread.
+ *
+ * @param rootCause A string containing the root cause of an exception.
+ * @param stackTrace A string containing the stack trace of an exception.
+ * @return None.
+ */
+void setTLSExceptionStrings(const char *rootCause, const char *stackTrace);
+
 /**
  * Figure out if a Java object is an instance of a particular class.
  *

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/os/posix/thread_local_storage.c

@@ -19,6 +19,7 @@
 #include "os/thread_local_storage.h"
 
 #include <jni.h>
+#include <malloc.h>
 #include <pthread.h>
 #include <stdio.h>
 
@@ -34,23 +35,48 @@ static int gTlsKeyInitialized = 0;
  *
  * @param v         The thread-local data
  */
-static void hdfsThreadDestructor(void *v)
+void hdfsThreadDestructor(void *v)
 {
   JavaVM *vm;
-  JNIEnv *env = v;
+  struct ThreadLocalState *state = (struct ThreadLocalState*)v;
+  JNIEnv *env = state->env;;
   jint ret;
 
-  ret = (*env)->GetJavaVM(env, &vm);
-  if (ret) {
-    fprintf(stderr, "hdfsThreadDestructor: GetJavaVM failed with error %d\n",
-      ret);
-    (*env)->ExceptionDescribe(env);
-  } else {
-    (*vm)->DetachCurrentThread(vm);
+  /* Detach the current thread from the JVM */
+  if (env) {
+    ret = (*env)->GetJavaVM(env, &vm);
+    if (ret) {
+      fprintf(stderr, "hdfsThreadDestructor: GetJavaVM failed with error %d\n",
+        ret);
+      (*env)->ExceptionDescribe(env);
+    } else {
+      (*vm)->DetachCurrentThread(vm);
+    }
+  }
+
+  /* Free exception strings */
+  if (state->lastExceptionStackTrace) free(state->lastExceptionStackTrace);
+  if (state->lastExceptionRootCause) free(state->lastExceptionRootCause);
+
+  /* Free the state itself */
+  free(state);
+}
+
+struct ThreadLocalState* threadLocalStorageCreate()
+{
+  struct ThreadLocalState *state;
+  state = (struct ThreadLocalState*)malloc(sizeof(struct ThreadLocalState));
+  if (state == NULL) {
+    fprintf(stderr,
+      "threadLocalStorageSet: OOM - Unable to allocate thread local state\n");
+    return NULL;
   }
+  state->lastExceptionStackTrace = NULL;
+  state->lastExceptionRootCause = NULL;
+  return state;
 }
 
-int threadLocalStorageGet(JNIEnv **env)
+int threadLocalStorageGet(struct ThreadLocalState **state)
 {
   int ret = 0;
   if (!gTlsKeyInitialized) {
@@ -63,18 +89,18 @@ int threadLocalStorageGet(JNIEnv **env)
     }
     gTlsKeyInitialized = 1;
   }
-  *env = pthread_getspecific(gTlsKey);
+  *state = pthread_getspecific(gTlsKey);
   return ret;
 }
 
-int threadLocalStorageSet(JNIEnv *env)
+int threadLocalStorageSet(struct ThreadLocalState *state)
 {
-  int ret = pthread_setspecific(gTlsKey, env);
+  int ret = pthread_setspecific(gTlsKey, state);
   if (ret) {
     fprintf(stderr,
       "threadLocalStorageSet: pthread_setspecific failed with error %d\n",
       ret);
-    hdfsThreadDestructor(env);
+    hdfsThreadDestructor(state);
   }
   return ret;
 }

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/os/thread_local_storage.h

@@ -34,42 +34,67 @@
  * operating systems that support it.
  */
 #ifdef HAVE_BETTER_TLS
-  #define THREAD_LOCAL_STORAGE_GET_QUICK() \
-    static __thread JNIEnv *quickTlsEnv = NULL; \
+  #define THREAD_LOCAL_STORAGE_GET_QUICK(state) \
+    static __thread struct ThreadLocalState *quickTlsEnv = NULL; \
     { \
       if (quickTlsEnv) { \
-        return quickTlsEnv; \
+        *state = quickTlsEnv; \
       } \
     }
 
-  #define THREAD_LOCAL_STORAGE_SET_QUICK(env) \
+  #define THREAD_LOCAL_STORAGE_SET_QUICK(state) \
     { \
-      quickTlsEnv = (env); \
+      quickTlsEnv = (state); \
     }
 #else
-  #define THREAD_LOCAL_STORAGE_GET_QUICK()
-  #define THREAD_LOCAL_STORAGE_SET_QUICK(env)
+  #define THREAD_LOCAL_STORAGE_GET_QUICK(state)
+  #define THREAD_LOCAL_STORAGE_SET_QUICK(state)
 #endif
 
+struct ThreadLocalState {
+  /* The JNIEnv associated with the current thread */
+  JNIEnv *env;
+  /* The last exception stack trace that occured on this thread */
+  char *lastExceptionStackTrace;
+  /* The last exception root cause that occured on this thread */
+  char *lastExceptionRootCause;
+};
+
+/**
+ * The function that is called whenever a thread with libhdfs thread local data
+ * is destroyed.
+ *
+ * @param v         The thread-local data
+ */
+void hdfsThreadDestructor(void *v);
+
+/**
+ * Creates an object of ThreadLocalState.
+ *
+ * @return The newly created object if successful, NULL otherwise.
+ */
+struct ThreadLocalState* threadLocalStorageCreate();
+
 /**
- * Gets the JNIEnv in thread-local storage for the current thread.  If the call
- * succeeds, and there is a JNIEnv associated with this thread, then returns 0
- * and populates env.  If the call succeeds, but there is no JNIEnv associated
- * with this thread, then returns 0 and sets JNIEnv to NULL.  If the call fails,
- * then returns non-zero.  Only one thread at a time may execute this function.
- * The caller is responsible for enforcing mutual exclusion.
+ * Gets the ThreadLocalState in thread-local storage for the current thread.
+ * If the call succeeds, and there is a ThreadLocalState associated with this
+ * thread, then returns 0 and populates 'state'.  If the call succeeds, but
+ * there is no ThreadLocalState associated with this thread, then returns 0
+ * and sets ThreadLocalState to NULL. If the call fails, then returns non-zero.
+ * Only one thread at a time may execute this function. The caller is
+ * responsible for enforcing mutual exclusion.
  *
- * @param env JNIEnv out parameter
+ * @param env ThreadLocalState out parameter
  * @return 0 if successful, non-zero otherwise
  */
-int threadLocalStorageGet(JNIEnv **env);
+int threadLocalStorageGet(struct ThreadLocalState **state);
 
 /**
- * Sets the JNIEnv in thread-local storage for the current thread.
+ * Sets the ThreadLocalState in thread-local storage for the current thread.
  *
- * @param env JNIEnv to set
+ * @param env ThreadLocalState to set
  * @return 0 if successful, non-zero otherwise
  */
-int threadLocalStorageSet(JNIEnv *env);
+int threadLocalStorageSet(struct ThreadLocalState *state);
 
 #endif

hadoop-hdfs-project/hadoop-hdfs-native-client/src/main/native/libhdfs/os/windows/thread_local_storage.c

@@ -19,6 +19,7 @@
 #include "os/thread_local_storage.h"
 
 #include <jni.h>
+#include <malloc.h>
 #include <stdio.h>
 #include <windows.h>
 
@@ -27,16 +28,21 @@ static DWORD gTlsIndex = TLS_OUT_OF_INDEXES;
 
 /**
  * If the current thread has a JNIEnv in thread-local storage, then detaches the
- * current thread from the JVM.
+ * current thread from the JVM and also frees up the ThreadLocalState object.
  */
 static void detachCurrentThreadFromJvm()
 {
+  struct ThreadLocalState *state = NULL;
   JNIEnv *env = NULL;
   JavaVM *vm;
   jint ret;
-  if (threadLocalStorageGet(&env) || !env) {
+  if (threadLocalStorageGet(&state) || !state) {
     return;
   }
+  if (!state->env) {
+    return;
+  }
+  env = state->env;
   ret = (*env)->GetJavaVM(env, &vm);
   if (ret) {
     fprintf(stderr,
@@ -46,6 +52,13 @@ static void detachCurrentThreadFromJvm()
   } else {
     (*vm)->DetachCurrentThread(vm);
   }
+
+  /* Free exception strings */
+  if (state->lastExceptionStackTrace) free(state->lastExceptionStackTrace);
+  if (state->lastExceptionRootCause) free(state->lastExceptionRootCause);
+
+  /* Free the state itself */
+  free(state);
 }
 
 /**
@@ -122,7 +135,21 @@ extern const PIMAGE_TLS_CALLBACK pTlsCallback;
 const PIMAGE_TLS_CALLBACK pTlsCallback = tlsCallback;
 #pragma const_seg()
 
-int threadLocalStorageGet(JNIEnv **env)
+struct ThreadLocalState* threadLocalStorageCreate()
+{
+  struct ThreadLocalState *state;
+  state = (struct ThreadLocalState*)malloc(sizeof(struct ThreadLocalState));
+  if (state == NULL) {
+    fprintf(stderr,
+      "threadLocalStorageSet: OOM - Unable to allocate thread local state\n");
+    return NULL;
+  }
+  state->lastExceptionStackTrace = NULL;
+  state->lastExceptionRootCause = NULL;
+  return state;
+}
+
+int threadLocalStorageGet(struct ThreadLocalState **state)
 {
   LPVOID tls;
   DWORD ret;
@@ -137,13 +164,13 @@ int threadLocalStorageGet(JNIEnv **env)
   }
   tls = TlsGetValue(gTlsIndex);
   if (tls) {
-    *env = tls;
+    *state = tls;
     return 0;
   } else {
     ret = GetLastError();
     if (ERROR_SUCCESS == ret) {
       /* Thread-local storage contains NULL, because we haven't set it yet. */
-      *env = NULL;
+      *state = NULL;
       return 0;
     } else {
       /*
@@ -158,15 +185,15 @@ int threadLocalStorageGet(JNIEnv **env)
   }
 }
 
-int threadLocalStorageSet(JNIEnv *env)
+int threadLocalStorageSet(struct ThreadLocalState *state)
 {
   DWORD ret = 0;
-  if (!TlsSetValue(gTlsIndex, (LPVOID)env)) {
+  if (!TlsSetValue(gTlsIndex, (LPVOID)state)) {
     ret = GetLastError();
     fprintf(stderr,
       "threadLocalStorageSet: TlsSetValue failed with error %d\n",
       ret);
-    detachCurrentThreadFromJvm(env);
+    detachCurrentThreadFromJvm(state);
   }
   return ret;
 }