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, 13 insertions, 11 deletions

diff --git a/gdb/alpha-tdep.h b/gdb/alpha-tdep.h
index c1fd694..c1674fe 100644
--- a/gdb/alpha-tdep.h
+++ b/gdb/alpha-tdep.h
@@ -19,6 +19,8 @@
 #ifndef ALPHA_TDEP_H
 #define ALPHA_TDEP_H
 
+#include "gdbarch.h"
+
 struct regcache;
 
 /* Say how long (ordinary) registers are.  This is a piece of bogosity
@@ -68,38 +70,38 @@ struct regcache;
 #define ALPHA_NUM_ARG_REGS   6
 
 /* Target-dependent structure in gdbarch.  */
-struct gdbarch_tdep
+struct alpha_gdbarch_tdep : gdbarch_tdep
 {
-  CORE_ADDR vm_min_address;	/* Used by alpha_heuristic_proc_start.  */
+  CORE_ADDR vm_min_address = 0;	/* Used by alpha_heuristic_proc_start.  */
 
   /* If PC is inside a dynamically-generated signal trampoline function
      (i.e. one copied onto the user stack at run-time), return how many
      bytes PC is beyond the start of that function.  Otherwise, return -1.  */
-  LONGEST (*dynamic_sigtramp_offset) (struct gdbarch *, CORE_ADDR);
+  LONGEST (*dynamic_sigtramp_offset) (struct gdbarch *, CORE_ADDR) = nullptr;
 
   /* Translate a signal handler stack base address into the address of
      the sigcontext structure for that signal handler.  */
-  CORE_ADDR (*sigcontext_addr) (struct frame_info *);
+  CORE_ADDR (*sigcontext_addr) (struct frame_info *) = nullptr;
 
   /* Does the PC fall in a signal trampoline.  */
   /* NOTE: cagney/2004-04-30: Do not copy/clone this code.  Instead
      look at tramp-frame.h and other simpler per-architecture
      sigtramp unwinders.  */
   int (*pc_in_sigtramp) (struct gdbarch *gdbarch, CORE_ADDR pc,
-			 const char *name);
+			 const char *name) = nullptr;
 
   /* If TYPE will be returned in memory, return true.  */
-  int (*return_in_memory) (struct type *type);
+  int (*return_in_memory) (struct type *type) = nullptr;
 
   /* Offset of registers in `struct sigcontext'.  */
-  int sc_pc_offset;
-  int sc_regs_offset;
-  int sc_fpregs_offset;
+  int sc_pc_offset = 0;
+  int sc_regs_offset = 0;
+  int sc_fpregs_offset = 0;
 
-  int jb_pc;			/* Offset to PC value in jump buffer.
+  int jb_pc = 0;			/* Offset to PC value in jump buffer.
 				   If htis is negative, longjmp support
 				   will be disabled.  */
-  size_t jb_elt_size;		/* And the size of each entry in the buf.  */
+  size_t jb_elt_size = 0;		/* And the size of each entry in the buf.  */
 };
 
 extern unsigned int alpha_read_insn (struct gdbarch *gdbarch, CORE_ADDR pc);