Re: JNI assertion failure

[Archie Cobbs]

Archie Cobbs wrote:
> > With Classpath 0.16, trying to run a very simple Swing demo under JCVM,
> > I get a JNI assertion failure in a call to GetIntField(), because the 
> > object
> > type and the fieldID are not compatible:
> >
> >    gnu/java/awt/peer/gtk/address@hidden not instance of 
> > gnu/java/awt/peer/gtk/GtkGenericPeer
> >
> > Here is the relevant stack trace snippet:
> >
> > #7  0x29f862d7 in 
> > Java_gnu_java_awt_peer_gtk_GdkGraphics_initState__Lgnu_java_awt_peer_gtk_GtkComponentPeer_2 
> > (env=0x107ed6a0, obj=0x29795698, peer=0x2979569c)
> >     at gnu_java_awt_peer_gtk_GdkGraphics.c:154
>
> Hmm, no response.. can anyone else confirm this problem??
>
> It looks like this code is completely broken, because
> it's trying to save a pointer in a field that doesn't
> exist. Line 154 of gnu_java_awt_peer_gtk_GdkGraphics.c says:
>
>   NSA_SET_PTR (env, obj, g)
>
> but "obj" is a gnu/java/awt/peer/gtk/GdkGraphics object, not
> a gnu/java/awt/peer/gtk/GtkGenericPeer object, the class that
> contains the "native_state" field.

Since nobody seems to be listening, I'm going to check in the
attached patch. This will cause all programs that use the GTK
peer to crash with an assertion failure. Sorry! The code
is broken but I don't know how to fix it. At least now we get
an assertion failure instead of random memory corruption.

You have been warned :-)

-Archie

__________________________________________________________________________
Archie Cobbs      *        CTO, Awarix        *      http://www.awarix.com

Index: native/jni/classpath/native_state.c
===================================================================
RCS file: /cvsroot/classpath/classpath/native/jni/classpath/native_state.c,v
retrieving revision 1.11
diff -u -r1.11 native_state.c
--- native/jni/classpath/native_state.c 14 Jul 2005 22:07:02 -0000      1.11
+++ native/jni/classpath/native_state.c 23 Jul 2005 19:30:28 -0000
@@ -36,6 +36,7 @@
 exception statement from your version. */
 
 #include <stdlib.h>
+#include <assert.h>
 #include <jni.h>
 #include "native_state.h"
 
@@ -214,6 +215,10 @@
 cp_gtk_set_state (JNIEnv * env, jobject obj, struct state_table *table, void 
*state)
 {
   jint obj_id;
+
+  assert ((*env)->IsAssignableFrom(env,
+    (*env)->GetObjectClass(env, obj), table->clazz));
+
   obj_id = (*env)->GetIntField (env, obj, table->hash);
 
   if ((*env)->ExceptionOccurred (env) != NULL)
@@ -227,6 +232,10 @@
 cp_gtk_get_state (JNIEnv * env, jobject obj, struct state_table *table)
 {
   jint obj_id;
+
+  assert ((*env)->IsAssignableFrom(env,
+    (*env)->GetObjectClass(env, obj), table->clazz));
+
   obj_id = (*env)->GetIntField (env, obj, table->hash);
 
   if ((*env)->ExceptionOccurred (env) != NULL)
@@ -239,6 +248,10 @@
 cp_gtk_remove_state_slot (JNIEnv * env, jobject obj, struct state_table *table)
 {
   jint obj_id;
+
+  assert ((*env)->IsAssignableFrom(env,
+    (*env)->GetObjectClass(env, obj), table->clazz));
+
   obj_id = (*env)->GetIntField (env, obj, table->hash);
 
   if ((*env)->ExceptionOccurred (env) != NULL)