gdb: rename gdbarch_tdep struct to fix g++ 4.8 build

After the commit:

  commit 08106042d9f5fdff60c129bf33190639f1a98b2a
  Date:   Thu May 19 13:20:17 2022 +0100

      gdb: move the type cast into gdbarch_tdep

GDB would no longer build using g++ 4.8.  The issue appears to be some
confusion caused by GDB having 'struct gdbarch_tdep', but also a
templated function called 'gdbarch_tdep'.  Prior to the above commit
the gdbarch_tdep function was not templated, and this compiled just
fine.  Note that the above commit compiles just fine with later
versions of g++, so this issue was clearly fixed at some point, though
I've not tried to track down exactly when.

In this commit I propose to fix the g++ 4.8 build problem by renaming
'struct gdbarch_tdep' to 'struct gdbarch_tdep_base'.  This rename
better represents that the struct is only ever used as a base class,
and removes the overloading of the name, which allows GDB to build
with g++ 4.8.

I've also updated the comment on 'struct gdbarch_tdep_base' to fix a
typo, and the comment on the 'gdbarch_tdep' function, to mention that
in maintainer mode a run-time type check is performed.

1 files changed, 14 insertions, 11 deletions

diff --git a/gdb/gdbarch.h b/gdb/gdbarch.h
index 16c7391..3249584 100644
--- a/gdb/gdbarch.h
+++ b/gdb/gdbarch.h
@@ -61,11 +61,11 @@ struct inferior;
 
 /* The base class for every architecture's tdep sub-class.  The virtual
    destructor ensures the class has RTTI information, which allows
-   gdb::checked_static_cast to be used, the gdbarch_tdep the function.  */
+   gdb::checked_static_cast to be used in the gdbarch_tdep function.  */
 
-struct gdbarch_tdep
+struct gdbarch_tdep_base
 {
-  virtual ~gdbarch_tdep() = default;
+  virtual ~gdbarch_tdep_base() = default;
 };
 
 /* The architecture associated with the inferior through the
@@ -151,20 +151,23 @@ using read_core_file_mappings_loop_ftype =
 #include "gdbarch-gen.h"
 
 /* An internal function that should _only_ be called from gdbarch_tdep.
-   Returns the gdbarch_tdep field held within GDBARCH.  */
+   Returns the gdbarch_tdep_base field held within GDBARCH.  */
 
-extern struct gdbarch_tdep *gdbarch_tdep_1 (struct gdbarch *gdbarch);
+extern struct gdbarch_tdep_base *gdbarch_tdep_1 (struct gdbarch *gdbarch);
 
-/* Return the gdbarch_tdep object held within GDBARCH cast to the type
-   TDepType, which should be a sub-class of gdbarch_tdep.  There is no
-   checking done that the gdbarch_tdep within GDBARCH actually is of the
-   type TDepType, we just assume the caller knows what they are doing.  */
+/* Return the gdbarch_tdep_base object held within GDBARCH cast to the type
+   TDepType, which should be a sub-class of gdbarch_tdep_base.
+
+   When GDB is compiled in maintainer mode a run-time check is performed
+   that the gdbarch_tdep_base within GDBARCH really is of type TDepType.
+   When GDB is compiled in release mode the run-time check is not
+   performed, and we assume the caller knows what they are doing.  */
 
 template<typename TDepType>
 static inline TDepType *
 gdbarch_tdep (struct gdbarch *gdbarch)
 {
-  struct gdbarch_tdep *tdep = gdbarch_tdep_1 (gdbarch);
+  struct gdbarch_tdep_base *tdep = gdbarch_tdep_1 (gdbarch);
   return gdb::checked_static_cast<TDepType *> (tdep);
 }
 
@@ -293,7 +296,7 @@ extern struct gdbarch_list *gdbarch_list_lookup_by_info (struct gdbarch_list *ar
    parameters.  set_gdbarch_*() functions are called to complete the
    initialization of the object.  */
 
-extern struct gdbarch *gdbarch_alloc (const struct gdbarch_info *info, struct gdbarch_tdep *tdep);
+extern struct gdbarch *gdbarch_alloc (const struct gdbarch_info *info, struct gdbarch_tdep_base *tdep);
 
 
 /* Helper function.  Free a partially-constructed ``struct gdbarch''.