Patch: FYI: Fix PR 18278

[Tom Tromey]

I'm checking this in on the trunk and the 4.1 branch.

This fixes PR 18278.  Now we unwrap the return value of a JNI method
if the method returns an object.  This lets us correctly handle user
functions which return JNI weak references.  We hit this while running
a java-gnome application.

Test case included.

Tom

Index: gcc/java/ChangeLog
from  Tom Tromey  <tromey@redhat.com>

	PR java/18278:
	* expr.c (build_jni_stub): Unwrap the return value.
	* java-tree.h (soft_unwrapjni_node): New define.
	(enum java_tree_index): Added JTI_SOFT_UNWRAPJNI_NODE.
	* decl.c (java_init_decl_processing): Initialize
	soft_unwrapjni_node.

Index: libjava/ChangeLog
from  Tom Tromey  <tromey@redhat.com>

	PR java/18278:
	* testsuite/libjava.jni/pr18278.out: New file.
	* testsuite/libjava.jni/pr18278.c: New file.
	* testsuite/libjava.jni/pr18278.java: New file.
	* include/jvm.h (_Jv_UnwrapJNIweakReference): Declare.
	* jni.cc (_Jv_UnwrapJNIweakReference): New function.
	(call): Unwrap return value if needed.

Index: gcc/java/decl.c
===================================================================
--- gcc/java/decl.c	(revision 107670)
+++ gcc/java/decl.c	(working copy)
@@ -1169,6 +1169,12 @@
 			build_function_type (void_type_node, t),
 			0, NOT_BUILT_IN, NULL, NULL_TREE);
 
+  t = tree_cons (NULL_TREE, object_ptr_type_node, endlink);
+  soft_unwrapjni_node
+    = builtin_function ("_Jv_UnwrapJNIweakReference",
+			build_function_type (object_ptr_type_node, t),
+			0, NOT_BUILT_IN, NULL, NULL_TREE);
+
   t = tree_cons (NULL_TREE, int_type_node,
 		 tree_cons (NULL_TREE, int_type_node, endlink));
   soft_idiv_node
Index: gcc/java/expr.c
===================================================================
--- gcc/java/expr.c	(revision 107670)
+++ gcc/java/expr.c	(working copy)
@@ -2558,8 +2558,17 @@
   /* If the JNI call returned a result, capture it here.  If we had to
      unwrap JNI object results, we would do that here.  */
   if (res_var != NULL_TREE)
-    call = build2 (MODIFY_EXPR, TREE_TYPE (TREE_TYPE (method)),
-		   res_var, call);
+    {
+      /* If the call returns an object, it may return a JNI weak
+	 reference, in which case we must unwrap it.  */
+      if (! JPRIMITIVE_TYPE_P (TREE_TYPE (TREE_TYPE (method))))
+	call = build3 (CALL_EXPR, TREE_TYPE (TREE_TYPE (method)),
+		       build_address_of (soft_unwrapjni_node),
+		       build_tree_list (NULL_TREE, call),
+		       NULL_TREE);
+      call = build2 (MODIFY_EXPR, TREE_TYPE (TREE_TYPE (method)),
+		     res_var, call);
+    }
 
   TREE_SIDE_EFFECTS (call) = 1;
   CAN_COMPLETE_NORMALLY (call) = 1;
Index: gcc/java/java-tree.h
===================================================================
--- gcc/java/java-tree.h	(revision 107670)
+++ gcc/java/java-tree.h	(working copy)
@@ -394,6 +394,7 @@
   JTI_SOFT_LOOKUPJNIMETHOD_NODE,
   JTI_SOFT_GETJNIENVNEWFRAME_NODE,
   JTI_SOFT_JNIPOPSYSTEMFRAME_NODE,
+  JTI_SOFT_UNWRAPJNI_NODE,
   JTI_SOFT_FMOD_NODE,
   JTI_SOFT_IDIV_NODE,
   JTI_SOFT_IREM_NODE,
@@ -663,6 +664,8 @@
   java_global_trees[JTI_SOFT_GETJNIENVNEWFRAME_NODE]
 #define soft_jnipopsystemframe_node \
   java_global_trees[JTI_SOFT_JNIPOPSYSTEMFRAME_NODE]
+#define soft_unwrapjni_node \
+  java_global_trees[JTI_SOFT_UNWRAPJNI_NODE]
 #define soft_fmod_node \
   java_global_trees[JTI_SOFT_FMOD_NODE]
 #define soft_idiv_node \
Index: libjava/include/jvm.h
===================================================================
--- libjava/include/jvm.h	(revision 107670)
+++ libjava/include/jvm.h	(working copy)
@@ -459,6 +459,8 @@
 extern "C" void _Jv_RegisterResource (void *vptr);
 extern void _Jv_UnregisterClass (_Jv_Utf8Const*, java::lang::ClassLoader*);
 
+extern "C" jobject _Jv_UnwrapJNIweakReference (jobject);
+
 extern jclass _Jv_FindClass (_Jv_Utf8Const *name,
 			     java::lang::ClassLoader *loader);
 extern jclass _Jv_FindClassFromSignature (char *,
Index: libjava/testsuite/libjava.jni/pr18278.java
===================================================================
--- libjava/testsuite/libjava.jni/pr18278.java	(revision 0)
+++ libjava/testsuite/libjava.jni/pr18278.java	(revision 0)
@@ -0,0 +1,13 @@
+public class pr18278 {
+    public pr18278() {}
+
+    public static void main(String[] args) {
+        System.loadLibrary("pr18278");
+	String bob = "Bob";
+	Object o = weakRef("Bob");
+	System.out.println(o);
+	System.out.println(bob == o);
+    }
+
+    static native Object weakRef(Object o);
+}
Index: libjava/testsuite/libjava.jni/pr18278.out
===================================================================
--- libjava/testsuite/libjava.jni/pr18278.out	(revision 0)
+++ libjava/testsuite/libjava.jni/pr18278.out	(revision 0)
@@ -0,0 +1,2 @@
+Bob
+true
Index: libjava/testsuite/libjava.jni/pr18278.c
===================================================================
--- libjava/testsuite/libjava.jni/pr18278.c	(revision 0)
+++ libjava/testsuite/libjava.jni/pr18278.c	(revision 0)
@@ -0,0 +1,10 @@
+#include <jni.h>
+#include <stdio.h>
+
+#include "pr18278.h"
+
+jobject Java_pr18278_weakRef(JNIEnv *env, jclass cls, jobject data)
+{
+  jobject r =  (* env)->NewWeakGlobalRef(env, data);
+  return r;
+}
Index: libjava/jni.cc
===================================================================
--- libjava/jni.cc	(revision 107670)
+++ libjava/jni.cc	(working copy)
@@ -226,6 +226,12 @@
   return reinterpret_cast<T *> (wr->get ());
 }
 
+jobject
+_Jv_UnwrapJNIweakReference (jobject obj)
+{
+  return unwrap (obj);
+}
+
 
 
 static jobject JNICALL
@@ -2304,6 +2310,13 @@
 		     ret, real_args);
 #endif
 
+  // We might need to unwrap a JNI weak reference here.
+  if (_this->jni_cif.rtype == &ffi_type_pointer)
+    {
+      _Jv_value *val = (_Jv_value *) ret;
+      val->object_value = unwrap (val->object_value);
+    }
+
   if (sync != NULL)
     _Jv_MonitorExit (sync);