gdb: fix gdbarch_tdep ODR violation

I would like to be able to use non-trivial types in gdbarch_tdep types.
This is not possible at the moment (in theory), because of the one
definition rule.

To allow it, rename all gdbarch_tdep types to <arch>_gdbarch_tdep, and
make them inherit from a gdbarch_tdep base class.  The inheritance is
necessary to be able to pass pointers to all these <arch>_gdbarch_tdep
objects to gdbarch_alloc, which takes a pointer to gdbarch_tdep.

These objects are never deleted through a base class pointer, so I
didn't include a virtual destructor.  In the future, if gdbarch objects
deletable, I could imagine that the gdbarch_tdep objects could become
owned by the gdbarch objects, and then it would become useful to have a
virtual destructor (so that the gdbarch object can delete the owned
gdbarch_tdep object).  But that's not necessary right now.

It turns out that RISC-V already has a gdbarch_tdep that is
non-default-constructible, so that provides a good motivation for this
change.

Most changes are fairly straightforward, mostly needing to add some
casts all over the place.  There is however the xtensa architecture,
doing its own little weird thing to define its gdbarch_tdep.  I did my
best to adapt it, but I can't test those changes.

Change-Id: Ic001903f91ddd106bd6ca09a79dabe8df2d69f3b

1 files changed, 19 insertions, 9 deletions

diff --git a/gdb/mep-tdep.c b/gdb/mep-tdep.c
index d48e1f117a7..6d1f04a2ab2 100644
--- a/gdb/mep-tdep.c
+++ b/gdb/mep-tdep.c
@@ -116,7 +116,7 @@
      options are present on the current processor.  */
 
 
-struct gdbarch_tdep
+struct mep_gdbarch_tdep : gdbarch_tdep
 {
   /* A CGEN cpu descriptor for this BFD architecture and machine.
 
@@ -124,7 +124,7 @@ struct gdbarch_tdep
      MeP libopcodes machinery actually puts off module-specific
      customization until the last minute.  So this contains
      information about all supported me_modules.  */
-  CGEN_CPU_DESC cpu_desc;
+  CGEN_CPU_DESC cpu_desc = nullptr;
 
   /* The me_module index from the ELF file we used to select this
      architecture, or CONFIG_NONE if there was none.
@@ -140,7 +140,7 @@ struct gdbarch_tdep
      create a separate instance of the gdbarch structure for each
      me_module value mep_gdbarch_init sees, and store the me_module
      value from the ELF file here.  */
-  CONFIG_ATTR me_module;
+  CONFIG_ATTR me_module {};
 };
 
 
@@ -259,7 +259,9 @@ me_module_register_set (CONFIG_ATTR me_module,
        mask contains any of the me_module's coprocessor ISAs,
        specifically excluding the generic coprocessor register sets.  */
 
-  CGEN_CPU_DESC desc = gdbarch_tdep (target_gdbarch ())->cpu_desc;
+  mep_gdbarch_tdep *tdep
+    = (mep_gdbarch_tdep *) gdbarch_tdep (target_gdbarch ());
+  CGEN_CPU_DESC desc = tdep->cpu_desc;
   const CGEN_HW_ENTRY *hw;
 
   if (me_module == CONFIG_NONE)
@@ -852,7 +854,11 @@ current_me_module (void)
       return (CONFIG_ATTR) regval;
     }
   else
-    return gdbarch_tdep (target_gdbarch ())->me_module;
+    {
+      mep_gdbarch_tdep *tdep
+	= (mep_gdbarch_tdep *) gdbarch_tdep (target_gdbarch ());
+      return tdep->me_module;
+    }
 }
 
 
@@ -2326,7 +2332,6 @@ static struct gdbarch *
 mep_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 {
   struct gdbarch *gdbarch;
-  struct gdbarch_tdep *tdep;
 
   /* Which me_module are we building a gdbarch object for?  */
   CONFIG_ATTR me_module;
@@ -2384,10 +2389,15 @@ mep_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   for (arches = gdbarch_list_lookup_by_info (arches, &info); 
        arches != NULL;
        arches = gdbarch_list_lookup_by_info (arches->next, &info))
-    if (gdbarch_tdep (arches->gdbarch)->me_module == me_module)
-      return arches->gdbarch;
+    {
+      mep_gdbarch_tdep *tdep
+	= (mep_gdbarch_tdep *) gdbarch_tdep (arches->gdbarch);
+
+      if (tdep->me_module == me_module)
+	return arches->gdbarch;
+    }
 
-  tdep = XCNEW (struct gdbarch_tdep);
+  mep_gdbarch_tdep *tdep = new mep_gdbarch_tdep;
   gdbarch = gdbarch_alloc (&info, tdep);
 
   /* Get a CGEN CPU descriptor for this architecture.  */