This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH] Fix early debug regression with DW_AT_string_length (PR debug/71906)


On Fri, Jul 22, 2016 at 2:08 PM, Jakub Jelinek <jakub@redhat.com> wrote:
> On Fri, Jul 22, 2016 at 01:55:22PM +0200, Richard Biener wrote:
>> > @@ -19201,18 +19205,70 @@ gen_array_type_die (tree type, dw_die_re
>> >        if (size >= 0)
>> >         add_AT_unsigned (array_die, DW_AT_byte_size, size);
>> >        else if (TYPE_DOMAIN (type) != NULL_TREE
>> > -              && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) != NULL_TREE
>> > -              && DECL_P (TYPE_MAX_VALUE (TYPE_DOMAIN (type))))
>> > +              && TYPE_MAX_VALUE (TYPE_DOMAIN (type)) != NULL_TREE)
>> >         {
>> >           tree szdecl = TYPE_MAX_VALUE (TYPE_DOMAIN (type));
>> > -         dw_loc_list_ref loc = loc_list_from_tree (szdecl, 2, NULL);
>> > +         tree rszdecl = szdecl;
>> > +         HOST_WIDE_INT rsize = 0;
>> >
>> >           size = int_size_in_bytes (TREE_TYPE (szdecl));
>> > -         if (loc && size > 0)
>> > +         if (!DECL_P (szdecl))
>> >             {
>> > -             add_AT_location_description (array_die, DW_AT_string_length, loc);
>> > -             if (size != DWARF2_ADDR_SIZE)
>> > -               add_AT_unsigned (array_die, DW_AT_byte_size, size);
>> > +             if (TREE_CODE (szdecl) == INDIRECT_REF
>>
>> So I wonder how this can happen with variable-size type
>> gimplification.  Shouldn't
>> this be on, say, DECL_VALUE_EXPR of the DECL_P TYPE_MAX_VALUE?
>
> If you mean the INDIRECT_REF, that only happens with PARM_DECLs, and
> conceptually a dereference of the argument is the right spot where the
> length lives (if you reallocate the string with different character length,
> then that is where you store the value.  If you add some artificial
> decl that will hold the value of *_varb, then the trouble is that the
> variable won't be assigned before the function prologue and most likely will
> be optimized away anyway.

True.  I wonder how other cases look like with the length not based on a
parameter.

>>  <1><28d>: Abbrev Number: 19 (DW_TAG_string_type)
>>  <1><28e>: Abbrev Number: 19 (DW_TAG_string_type)
>>  <1><28f>: Abbrev Number: 6 (DW_TAG_pointer_type)
>>
>> so there is nothing to annotate with a location later.
>
> With the patch there will be DW_OP_call4 in 2 DW_AT_string_length
> attributes and one DW_OP_call4; DW_OP_deref.
>
>> Note that even with GCC 5 'varb' didn't get a DW_AT_string_length,
>> 'vara' did, though.
>
> Yeah, I've mentioned that in the mail.
>
>         Jakub


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]