Re: [PATCH] gdb.trace: Fix string collection for 64-bit platforms.

[Pedro Alves <palves@redhat.com>]

On 01/21/2016 04:02 PM, Marcin Kościelnicki wrote:
> String collection always used ref32 to fetch the string pointer.  Make it
> use ref64 when pointeer size is 64-bit.

"pointer".

> 
> This appeared to work on x86_64 since it's a little-endian platform, and
> malloc (used in gdb.trace/collection.exp) returns addresses in low 4GB.
> Noticed and tested on s390x-ibm-linux-gnu, also tested on
> i686-unknown-linux-gnu and x86_64-unknown-linux-gnu.
> 
> gdb/ChangeLog:
> 
> 	* ax-gdb.c (gen_traced_pop): Use aop_ref64 when appropriate for
> 	string collection.
> ---
> OK to push?
> 
>  gdb/ChangeLog | 5 +++++
>  gdb/ax-gdb.c  | 5 ++++-
>  2 files changed, 9 insertions(+), 1 deletion(-)
> 
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 45d8ef9..3f4d152 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,8 @@
> +2016-01-21  Marcin Kościelnicki  <koriakin@0x04.net>
> +
> +	* ax-gdb.c (gen_traced_pop): Use aop_ref64 when appropriate for
> +	string collection.
> +
>  2016-01-21  Andrew Burgess  <andrew.burgess@embecosm.com>
>  
>  	* disasm.c (maybe_add_dis_line_entry): Rename to...
> diff --git a/gdb/ax-gdb.c b/gdb/ax-gdb.c
> index dd6eee6..d17cb04 100644
> --- a/gdb/ax-gdb.c
> +++ b/gdb/ax-gdb.c
> @@ -410,7 +410,10 @@ gen_traced_pop (struct gdbarch *gdbarch,
>  
>  	  if (string_trace)
>  	    {
> -	      ax_simple (ax, aop_ref32);
> +	      if (TYPE_LENGTH(value->type) == 4)

Missing space before parens.

> +	        ax_simple (ax, aop_ref32);
> +	      else
> +	        ax_simple (ax, aop_ref64);

> +	      if (TYPE_LENGTH(value->type) == 4)
> +	        ax_simple (ax, aop_ref32);
> +	      else
> +	        ax_simple (ax, aop_ref64);


Missing space before parens.  I was going to say to
check for == 8 instead so that we don't pessimize the
8/16 bits cases, but sounds better even to factor out
the switch in gen_fetch, so that the ref8/ref16 are covered
as well:

      switch (TYPE_LENGTH (type))
	{
	case 8 / TARGET_CHAR_BIT:
	  ax_simple (ax, aop_ref8);
	  break;
	case 16 / TARGET_CHAR_BIT:
	  ax_simple (ax, aop_ref16);
	  break;
	case 32 / TARGET_CHAR_BIT:
	  ax_simple (ax, aop_ref32);
	  break;
	case 64 / TARGET_CHAR_BIT:
	  ax_simple (ax, aop_ref64);
	  break;

	  /* Either our caller shouldn't have asked us to dereference
	     that pointer (other code's fault), or we're not
	     implementing something we should be (this code's fault).
	     In any case, it's a bug the user shouldn't see.  */
	default:
	  internal_error (__FILE__, __LINE__,

WDYT?

Thanks,
Pedro Alves