Use registry in gdbarch

gdbarch implements its own registry-like approach.  This patch changes
it to instead use registry.h.  It's a rather large patch but largely
uninteresting -- it's mostly a straightforward conversion from the old
approach to the new one.

The main benefit of this change is that it introduces type safety to
the gdbarch registry.  It also removes a bunch of code.

One possible drawback is that, previously, the gdbarch registry
differentiated between pre- and post-initialization setup.  This
doesn't seem very important to me, though.

1 files changed, 8 insertions, 14 deletions

diff --git a/gdb/linux-tdep.c b/gdb/linux-tdep.c
index 4e6a48b1d2..5fe6be16c3 100644
--- a/gdb/linux-tdep.c
+++ b/gdb/linux-tdep.c
@@ -193,25 +193,22 @@ enum
     LINUX_SIGRTMAX = 64,
   };
 
-static struct gdbarch_data *linux_gdbarch_data_handle;
-
 struct linux_gdbarch_data
 {
-  struct type *siginfo_type;
-  int num_disp_step_buffers;
+  struct type *siginfo_type = nullptr;
+  int num_disp_step_buffers = 0;
 };
 
-static void *
-init_linux_gdbarch_data (struct obstack *obstack)
-{
-  return obstack_zalloc<linux_gdbarch_data> (obstack);
-}
+static const registry<gdbarch>::key<linux_gdbarch_data>
+     linux_gdbarch_data_handle;
 
 static struct linux_gdbarch_data *
 get_linux_gdbarch_data (struct gdbarch *gdbarch)
 {
-  return ((struct linux_gdbarch_data *)
-	  gdbarch_data (gdbarch, linux_gdbarch_data_handle));
+  struct linux_gdbarch_data *result = linux_gdbarch_data_handle.get (gdbarch);
+  if (result == nullptr)
+    result = linux_gdbarch_data_handle.emplace (gdbarch);
+  return result;
 }
 
 /* Linux-specific cached data.  This is used by GDB for caching
@@ -2752,9 +2749,6 @@ void _initialize_linux_tdep ();
 void
 _initialize_linux_tdep ()
 {
-  linux_gdbarch_data_handle =
-    gdbarch_data_register_pre_init (init_linux_gdbarch_data);
-
   /* Observers used to invalidate the cache when needed.  */
   gdb::observers::inferior_exit.attach (invalidate_linux_cache_inf,
 					"linux-tdep");