Re: [PATCH 3/7]: Regcache: Remove xmalloc/xfree methods

[Yao Qi <qiyaoltc at gmail dot com>]

Alan Hayward <Alan.Hayward@arm.com> writes:

> Regcache is a class. There is no need for explicit xmalloc
> and xfree methods, it is much simpler to use new and delete.
>

new/delete isn't simpler than xmalloc/xfree, IMO.  We still need to take
care of releasing resources.

>
> diff --git a/gdb/frame.c b/gdb/frame.c
> index 30e4aeab7e2901074c289ac4d96ebda885805a29..7fd4b07a2e95f28b2eb6a18dea4d2071f0ece4e2 100644
> --- a/gdb/frame.c
> +++ b/gdb/frame.c
> @@ -1021,13 +1021,12 @@ struct regcache *
> frame_save_as_regcache (struct frame_info *this_frame)
> {
>   struct address_space *aspace = get_frame_address_space (this_frame);
> -  struct regcache *regcache = regcache_xmalloc (get_frame_arch (this_frame),
> -						aspace);
> -  struct cleanup *cleanups = make_cleanup_regcache_xfree (regcache);
> +  regcache *backup = new regcache (get_frame_arch (this_frame), aspace);
> +  struct cleanup *cleanups = make_cleanup_regcache_delete (backup);
>

It makes no sense to change make_cleanup_regcache_xfree to
make_cleanup_regcache_delete.  We still have to use cleanup.

> -  regcache_save (regcache, do_frame_register_read, this_frame);
> +  regcache_save (backup, do_frame_register_read, this_frame);
>   discard_cleanups (cleanups);
> -  return regcache;
> +  return backup;
> }
>
> void
> @@ -1063,7 +1062,7 @@ frame_pop (struct frame_info *this_frame)
>      trying to extract the old values from the current regcache while
>      at the same time writing new values into that same cache.  */
>   scratch = frame_save_as_regcache (prev_frame);
> -  cleanups = make_cleanup_regcache_xfree (scratch);
> +  cleanups = make_cleanup_regcache_delete (scratch);

scratch is only used within this function, so we can change it to a
local object (instead of a pointer), and call regcache_save here.  Then,
we can remove the cleanups.

> diff --git a/gdb/mi/mi-main.c b/gdb/mi/mi-main.c
> index 0bf587ffe702c68f538fe2877cce6114e64ee1bd..1edcf752c82230fc65669f675e10735ac8e4f654 100644
> --- a/gdb/mi/mi-main.c
> +++ b/gdb/mi/mi-main.c
> @@ -1051,7 +1051,7 @@ mi_cmd_data_list_changed_registers (const char *command, char **argv, int argc)
>
>   prev_regs = this_regs;
>   this_regs = frame_save_as_regcache (get_selected_frame (NULL));
> -  cleanup = make_cleanup_regcache_xfree (prev_regs);
> +  cleanup = make_cleanup_regcache_delete (prev_regs);

Why don't you do this? then, we don't need this make_cleanup_regcache_xfree.

std::unique_ptr<regcache> prev_regs (this_regs);

>
>   /* Note that the test for a valid register must include checking the
>      gdbarch_register_name because gdbarch_num_regs may be allocated
> diff --git a/gdb/ppc-linux-tdep.c b/gdb/ppc-linux-tdep.c
> index 324b29d90c1266a73f172da20a6015174189625f..42aff2cd1bf3834268b0b58dcf00dac1c52add96 100644
> --- a/gdb/ppc-linux-tdep.c
> +++ b/gdb/ppc-linux-tdep.c
> @@ -1364,13 +1364,13 @@ ppu2spu_sniffer (const struct frame_unwind *self,
> 	    = FRAME_OBSTACK_CALLOC (1, struct ppu2spu_cache);
>
> 	  struct address_space *aspace = get_frame_address_space (this_frame);
> -	  struct regcache *regcache = regcache_xmalloc (data.gdbarch, aspace);
> -	  struct cleanup *cleanups = make_cleanup_regcache_xfree (regcache);
> -	  regcache_save (regcache, ppu2spu_unwind_register, &data);
> +	  regcache *backup = new regcache (data.gdbarch, aspace);
> +	  struct cleanup *cleanups = make_cleanup_regcache_delete (backup);
> +	  regcache_save (backup, ppu2spu_unwind_register, &data);
> 	  discard_cleanups (cleanups);

We can use std::unique_ptr<regcache> too here.  After call
regcache_save, call .release () to return the raw pointer to cache->regcache.

>
> 	  cache->frame_id = frame_id_build (base, func);
> -	  cache->regcache = regcache;
> +	  cache->regcache = backup;
> 	  *this_prologue_cache = cache;
> 	  return 1;
> 	}
> @@ -1383,7 +1383,7 @@ static void
> ppu2spu_dealloc_cache (struct frame_info *self, void *this_cache)
> {
>   struct ppu2spu_cache *cache = (struct ppu2spu_cache *) this_cache;
> -  regcache_xfree (cache->regcache);
> +  delete cache->regcache;
> }
>
> static const struct frame_unwind ppu2spu_unwind = {
> diff --git a/gdb/regcache.h b/gdb/regcache.h
> index aeac54e8d7b91e2bcf6a3e1ce8e781c3f994306b..00b87db7d145205b74859c08ca5a9d852441a4aa 100644
> --- a/gdb/regcache.h
> +++ b/gdb/regcache.h
> @@ -36,10 +36,7 @@ extern target_regcache *get_thread_arch_aspace_regcache (ptid_t,
> 							 struct gdbarch *,
> 							 struct address_space *);
>
> -void regcache_xfree (struct regcache *regcache);
> -struct cleanup *make_cleanup_regcache_xfree (struct regcache *regcache);
> -struct regcache *regcache_xmalloc (struct gdbarch *gdbarch,
> -				   struct address_space *aspace);
> +struct cleanup *make_cleanup_regcache_delete (regcache *regcache);
>
> /* Return REGCACHE's ptid.  */
>
> @@ -261,12 +258,7 @@ public:
>   regcache (const regcache &) = delete;
>   void operator= (const regcache &) = delete;
>
> -  /* class regcache is only extended in unit test, so only mark it
> -     virtual when selftest is enabled.  */
> -#if GDB_SELF_TEST
> -  virtual
> -#endif
> -  ~regcache ()
> +  virtual ~regcache ()

This is not related to this patch.  It should be in patch #1.

-- 
Yao (齐尧)