[RFC] rl78: vtables are code addresses

[Kevin Buettner <kevinb at redhat dot com>]

This patch, for rl78 using the default multilib, fixes 5 failures in
gdb.cp/casts.exp, 2 failures in gdb.cp/class2.exp, 115 failures in
gdb.mi/mi-var-rtti.exp, and 2 failures in gdb.python/py-value.exp.

It introduces 9 failures (regressions) in gdb.mi/mi-var-rtti.exp.

One of the regressions is:

FAIL: gdb.mi/mi-var-rtti.exp: list children of s.public in type_update_when_use_rtti

The relevant lines from the log file from a pre-patch test run are as
follows:

-var-list-children  S.public  
^done,numchild="1",children=[child={name="S.public.ptr",exp="ptr",numchild="1",type="Base *",thread-id="1"}],has_more="0"
(gdb) 
PASS: gdb.mi/mi-var-rtti.exp: list children of s.public in type_update_when_use_rtti
Expecting: \^done,numchild=".*",children=\[child={name="S.public.ptr.public",exp="public",numchild="1"(,thread-id="[0-9]+")?}.*\],has_more="0"
Expecting: ^(-var-list-children  S\.public\.ptr  [
]+)?(\^done,numchild=".*",children=\[child={name="S.public.ptr.public",exp="public",numchild="1"(,thread-id="[0-9]+")?}.*\],has_more="0"[
]+[(]gdb[)] 
[ ]*)

------

The same set of lines for the failing (post-patch) run are instead:

-var-list-children  S.public  
&"warning: can't find linker symbol for virtual table for `Base' value\n"
&"warning:   found `typeinfo for __cxxabiv1::__vmi_class_type_info' instead\n"
&"warning: can't find linker symbol for virtual table for `Base' value\n"
&"warning:   found `typeinfo for __cxxabiv1::__vmi_class_type_info' instead\n"
&"warning: can't find linker symbol for virtual table for `Base' value\n"
&"warning:   found `typeinfo for __cxxabiv1::__vmi_class_type_info' instead\n"
^done,numchild="1",children=[child={name="S.public.ptr",exp="ptr",numchild="1",type="Base *",thread-id="1"}],has_more="0"
(gdb) 
FAIL: gdb.mi/mi-var-rtti.exp: list children of s.public in type_update_when_use_rtti
Expecting: \^done,numchild=".*",children=\[child={name="S.public.ptr.public",exp="public",numchild="1"(,thread-id="[0-9]+")?}.*\],has_more="0"
Expecting: ^(-var-list-children  S\.public\.ptr  [
]+)?(\^done,numchild=".*",children=\[child={name="S.public.ptr.public",exp="public",numchild="1"(,thread-id="[0-9]+")?}.*\],has_more="0"[
]+[(]gdb[)] 
[ ]*)

------

Note that the difference between these are the warnings regarding
linker symbols.  Aside from the warnings, the result is the same. 
I.e.  gdb produces the correct answer despite the warnings.  The
reason for the other 8 failures is the same:  the test harness is not
expecting these warnings.

I spent some time (a while ago) looking at the reason for these
warnings.  As I recall, we are now getting further along in the type
resolution process than we were without my patch.  I.e.  for the
example above, the code in question never got to the point where it
was looking for the specified linker symbol.  So it seems to me that,
at worst, my patch exposes some other problem, but is not directly
the cause of the problem.

I would like to commit this patch because, on balance, it markedly
improves the test results.  Without objection(s), I'll commit this
patch in a few days time.

Kevin

	* rl78-tdep.c (rl78_pointer_to_address): Add logic so that
	vtables are considered to be code addresses.

diff --git a/gdb/rl78-tdep.c b/gdb/rl78-tdep.c
index c28db4b..d067b43 100644
--- a/gdb/rl78-tdep.c
+++ b/gdb/rl78-tdep.c
@@ -764,14 +764,27 @@ rl78_pointer_to_address (struct gdbarch *gdbarch,
                          struct type *type, const gdb_byte *buf)
 {
   enum bfd_endian byte_order = gdbarch_byte_order (gdbarch);
+  int vtable = 0;
   CORE_ADDR addr
     = extract_unsigned_integer (buf, TYPE_LENGTH (type), byte_order);
 
+  /* See if it's a vtable.  */
+  if (TYPE_CODE (type) == TYPE_CODE_PTR)
+    {
+      struct type *targ_type = TYPE_TARGET_TYPE (type);
+       
+      if (TYPE_CODE (targ_type) == TYPE_CODE_STRUCT
+          && TYPE_TAG_NAME (targ_type) != NULL
+	  && strcmp (TYPE_TAG_NAME (targ_type), "gdb_gnu_v3_abi_vtable") == 0)
+	vtable = 1;
+    }
+
   /* Is it a code address?  */
   if (TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_FUNC
       || TYPE_CODE (TYPE_TARGET_TYPE (type)) == TYPE_CODE_METHOD
       || TYPE_CODE_SPACE (TYPE_TARGET_TYPE (type))
-      || TYPE_LENGTH (type) == 4)
+      || TYPE_LENGTH (type) == 4
+      || vtable)
     return rl78_make_instruction_address (addr);
   else
     return rl78_make_data_address (addr);