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, 8 insertions, 6 deletions

diff --git a/gdb/sh-tdep.h b/gdb/sh-tdep.h
index 737b6dc..fce3f71 100644
--- a/gdb/sh-tdep.h
+++ b/gdb/sh-tdep.h
@@ -19,6 +19,8 @@
 #ifndef SH_TDEP_H
 #define SH_TDEP_H
 
+#include "gdbarch.h"
+
 /* Contributed by Steve Chamberlain sac@cygnus.com.  */
 
 /* Registers for all SH variants.  Used also by sh3-rom.c.  */
@@ -89,20 +91,20 @@ struct sh_corefile_regmap
   unsigned int offset;
 };
 
-struct gdbarch_tdep
+struct sh_gdbarch_tdep : gdbarch_tdep
 {
   /* Non-NULL when debugging from a core file.  Provides the offset
      where each general-purpose register is stored inside the associated
      core file section.  */
-  struct sh_corefile_regmap *core_gregmap;
-  int sizeof_gregset;
+  struct sh_corefile_regmap *core_gregmap = nullptr;
+  int sizeof_gregset = 0;
   /* Non-NULL when debugging from a core file and when FP registers are
      available.  Provides the offset where each FP register is stored
      inside the associated core file section.  */
-  struct sh_corefile_regmap *core_fpregmap;
-  int sizeof_fpregset;
+  struct sh_corefile_regmap *core_fpregmap = nullptr;
+  int sizeof_fpregset = 0;
   /* ISA-specific data types.  */
-  struct type *sh_littlebyte_bigword_type;
+  struct type *sh_littlebyte_bigword_type = nullptr;
 };
 
 extern const struct regset sh_corefile_gregset;