Patch: RFC: alignment fix in resolve.cc

[Tom Tromey]

Last night I had a dream that told me about a potential bug in libgcj.
This morning I looked, and sure enough the recent alignment changes
weren't propagated to the runtime code that lays out interpreted
classes.

I believe there is no way to observe a bug here with 3.3.  I tried to
think of a case but couldn't.  (Maybe I'll have another dream to tell
me :-)

However, I think this problem could be visible on the trunk if using
-fno-assume-compiled.  And of course this will be an issue if/when
-findirect-dispatch is fully implemented.

Andrew, what do you think?

I haven't tested (or even compiled) this yet.
I wasn't sure how to get the alignment of the superclass, so the
patch just uses Object in all cases.  It seemed to me that that must
be ok; hopefully someone will tell me if I'm mistaken.

Tom

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

	* resolve.cc (_Jv_PrepareClass): Properly align first data member
	of class.

Index: libjava/resolve.cc
===================================================================
RCS file: /cvs/gcc/gcc/libjava/resolve.cc,v
retrieving revision 1.34.2.2
diff -u -r1.34.2.2 resolve.cc
--- libjava/resolve.cc 3 Feb 2003 21:04:50 -0000 1.34.2.2
+++ libjava/resolve.cc 13 Apr 2003 19:13:45 -0000
@@ -469,6 +469,7 @@
     instance_size = java::lang::Object::class$.size();
   static_size   = 0;
 
+  bool is_first_data_member = true;
   for (int i = 0; i < clz->field_count; i++)
     {
       int field_size;
@@ -506,6 +507,13 @@
 	}
       else
 	{
+	  if (is_first_data_member
+	      && field_align < __alignof__ (java::lang::Object))
+	    {
+	      is_first_data_member = false;
+	      field_align = __alignof__ (java::lang::Object);
+	    }
+
 	  instance_size      = ROUND (instance_size, field_align);
 	  field->u.boffset   = instance_size;
 	  instance_size     += field_size;