[RFA] dwarf2read.c: Avoid complaint for char array of unspecified size

[RFA] dwarf2read.c: Avoid complaint for char array of unspecified size

[Pierre Muller]

  When I tried to compile GDB on an Arm Linux,
I came across several complaint when debugging GDB with itself,
he is another patch.
  This code:
external char gdbint [];
generated a DW_TAG_subrange_type with zero attributes
to describe the `[]' part.
 (compiled with  gcc (Debian 4.3.2-1.1) 4.3.2.).

  As there was already some code that handled missing
children (for Irix), I simply extended it
to the case of a child with zero attributes.
  I implicitly supposed that there could be no child
to the subrange type die, which seems reasonable to me,
but others might have another opinion.
  I don't think it is possible to define a multiple
dimension array (matrix) in any language with one unspecified
length, am I right?

Pierre Muller
Pascal language support maintainer for GDB

 
2010-05-21  Pierre Muller  <muller@ics.u-strasbg.fr>

	* dwarf2read.c (read_array_type): Do not try to
	read subrange type with zero attributes.

Index: src/gdb/dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.386
diff -u -p -r1.386 dwarf2read.c
--- src/gdb/dwarf2read.c	17 May 2010 15:55:01 -0000	1.386
+++ src/gdb/dwarf2read.c	21 May 2010 14:47:42 -0000
@@ -5431,8 +5431,12 @@ read_array_type (struct die_info *die, s
   element_type = die_type (die, cu);
 
   /* Irix 6.2 native cc creates array types without children for
-     arrays with unspecified length.  */
-  if (die->child == NULL)
+     arrays with unspecified length.  
+     Likewise, for the following code:
+     extern char gdbinit [];
+     GCC generates a DW_TAG_subrange_type with zero attributes.  */
+  if (die->child == NULL || (die->child->tag == DW_TAG_subrange_type
+			     && die->child->num_attrs == 0))
     {
       index_type = objfile_type (objfile)->builtin_int;
       range_type = create_range_type (NULL, index_type, 0, -1);

Re: [RFA] dwarf2read.c: Avoid complaint for char array of unspecified size

[Tom Tromey]

>>>>> "Pierre" == Pierre Muller <pierre.muller@ics-cnrs.unistra.fr> writes:

Pierre>   This code:
Pierre> external char gdbint [];
Pierre> generated a DW_TAG_subrange_type with zero attributes
Pierre> to describe the `[]' part.
Pierre>  (compiled with  gcc (Debian 4.3.2-1.1) 4.3.2.).

I think this kind of DIE is explicitly ok, according to DWARF.
See the paragraph toward the end of section 5.11 that describes what to
do when a DW_TAG_subrange_type has no basis type.

So, I think this complaint is incorrect.  It would be better to simply
remove it.

Tom

RE: [RFA] dwarf2read.c: Avoid complaint for char array of unspecified size

[Pierre Muller]

> -----Message d'origine-----
> De : gdb-patches-owner@sourceware.org [mailto:gdb-patches-
> owner@sourceware.org] De la part de Tom Tromey
> Envoyé : Friday, May 21, 2010 11:43 PM
> À : Pierre Muller
> Cc : gdb-patches@sourceware.org
> Objet : Re: [RFA] dwarf2read.c: Avoid complaint for char array of
> unspecified size
> 
> >>>>> "Pierre" == Pierre Muller <pierre.muller@ics-cnrs.unistra.fr>
> writes:
> 
> Pierre>   This code:
> Pierre> external char gdbint [];
> Pierre> generated a DW_TAG_subrange_type with zero attributes
> Pierre> to describe the `[]' part.
> Pierre>  (compiled with  gcc (Debian 4.3.2-1.1) 4.3.2.).
> 
> I think this kind of DIE is explicitly ok, according to DWARF.
> See the paragraph toward the end of section 5.11 that describes what to
> do when a DW_TAG_subrange_type has no basis type.
 For dwarf2, in it on 5.10, page number 47 (49 of pdf file).
  If I understand this correctly, without anything it should be
a subrange of type "singed integer" having the same size as an address
for that target machine. This is not exactly what is done in the Irix
code I modified...
  But I still don't get the bounds that we should use:
  lower bound is 0, or 1 for fortran (default value),
but should upper bound be equal to lower bound or lower bound -1?

> So, I think this complaint is incorrect.  It would be better to simply
> remove it.
  This would mean that we should fix the code inside read_subrange_type, no?

  Do you think that this would be the correct approach?

Pierre

Re: [RFA] dwarf2read.c: Avoid complaint for char array of unspecified size

[Tom Tromey]

>>>>> "Pierre" == Pierre Muller <pierre.muller@ics-cnrs.unistra.fr> writes:

Pierre>   But I still don't get the bounds that we should use:
Pierre>   lower bound is 0, or 1 for fortran (default value),
Pierre> but should upper bound be equal to lower bound or lower bound -1?

Whatever means "unknown bounds" inside gdb.
I don't remember offhand what this is.

Pierre>   This would mean that we should fix the code inside
Pierre>   read_subrange_type, no?

Pierre>   Do you think that this would be the correct approach?

Yeah, I do.

Tom