[RFC] DW_AT_type missing from DW_TAG_subrange_type

[RFC] DW_AT_type missing from DW_TAG_subrange_type

[Denis PILAT]

For the global variable declared like that
  int array[] = {1, 2, 3, 4};
the dwarf information generated by our specific compiler is missing 
DW_AT_type missing from DW_TAG_subrange_type.

Usually in dwarf2 information (ie like the bellow example for gcc4 under 
linux), the DW_AT_type exists for subranges :

   < 175 (0xaf) > DW_TAG_array_type
   | DW_AT_sibling : < 191 (0xbf) >
   | DW_AT_type : < 168 (0xa8) >
   `--------------------------
      < 184 (0xb8) > DW_TAG_subrange_type
    * | DW_AT_type : < 191 (0xbf) >*          <<<<<-------- missing from 
my elf file
      | DW_AT_upper_bound : DW_AT_upper_bound(DW_FORM_data1) : 3
      `--------------------------


Therefore we go thru the code "base_type = alloc_type (NULL)" (in 
read_subrange_type of dwarf2read.c) and gdb prints the following if "set 
print array-indexes on": (all indexes are set to 0):
(gdb) p array
$1 = {[0] = 1, [0] = 2, [0] = 3, [0] = 4}

Could we have a *builtin_type_int* as the default type instead of 
alloc_type (NULL) ?
*Attach is a patch in that sense.*



I'm also wondering about  the code:
  base_type = die_type (die, cu);
  if (base_type == NULL)
    {
      complaint (&symfile_complaints,
                _("DW_AT_type missing from DW_TAG_subrange_type"));
      return;
    }
It seems we'll never have (base_type == NULL). Am I right ?
May be it's time to remove that as well. The complaints seems to be in a 
better place in my patch.


For information, this testcase is present in gdb.base/arrayidx.exp where 
we have "set print array-indexes on"

No regression for this patch for i386-linux target

-- 
Denis



Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.216
diff -u -p -r1.216 dwarf2read.c
--- dwarf2read.c        30 Mar 2007 17:21:47 -0000      1.216
+++ dwarf2read.c        3 Apr 2007 09:41:07 -0000
@@ -4921,7 +4921,11 @@ read_subrange_type (struct die_info *die
     }

   if (TYPE_CODE (base_type) == TYPE_CODE_VOID)
-    base_type = alloc_type (NULL);
+    {
+      complaint (&symfile_complaints,
+                _("DW_AT_type missing from DW_TAG_subrange_type"));
+      base_type = builtin_type_int;
+    }

   if (cu->language == language_fortran)
     {

Re: [RFC] DW_AT_type missing from DW_TAG_subrange_type

[Daniel Jacobowitz]

On Tue, Apr 03, 2007 at 03:23:56PM +0200, Denis PILAT wrote:
> For the global variable declared like that
>  int array[] = {1, 2, 3, 4};
> the dwarf information generated by our specific compiler is missing DW_AT_type 
> missing from DW_TAG_subrange_type.
> 
> Usually in dwarf2 information (ie like the bellow example for gcc4 under 
> linux), the DW_AT_type exists for subranges :
> 
>   < 175 (0xaf) > DW_TAG_array_type
>   | DW_AT_sibling : < 191 (0xbf) >
>   | DW_AT_type : < 168 (0xa8) >
>   `--------------------------
>      < 184 (0xb8) > DW_TAG_subrange_type
>    * | DW_AT_type : < 191 (0xbf) >*          <<<<<-------- missing from my elf 
> file
>      | DW_AT_upper_bound : DW_AT_upper_bound(DW_FORM_data1) : 3
>      `--------------------------

Conveniently, the DWARF 3 standard specifies what this means (DWARF 2
may also; I didn't check).  From the standard:

> If the subrange entry has no type attribute describing the basis type,
> the basis type is assumed to be the same as the object described by
> the lower bound attribute (if it references an object). If there is no
> lower bound attribute, or that attribute does not reference an object,
> the basis type is the type of the upper bound or count attribute (if
> either of them references an object). If there is no upper bound or
> count attribute, or neither references an object, the type is assumed
> to be the same type, in the source language of the compilation unit
> containing the subrange entry, as a signed integer with the same size
> as an address on the target machine.

Since we do not handle objects for bounds yet, we're only interested
in that last case.  So, we should use an integer type the size of an
address.  Try using dwarf_base_type (DW_ATE_signed, TARGET_ADDR_BIT /
8, cu)?

That function is, in fact, very buggy.  We should fix it.  It has
hardcoded sizes of 1, 2, 4 for char, short, int and doesn't support
long long at all.

> I'm also wondering about  the code:
>  base_type = die_type (die, cu);
>  if (base_type == NULL)
>    {
>      complaint (&symfile_complaints,
>                _("DW_AT_type missing from DW_TAG_subrange_type"));
>      return;
>    }
> It seems we'll never have (base_type == NULL). Am I right ?
> May be it's time to remove that as well. The complaints seems to be in a better 
> place in my patch.

You're right; please do.

-- 
Daniel Jacobowitz
CodeSourcery

Re: [RFC] DW_AT_type missing from DW_TAG_subrange_type

[Denis PILAT]

Daniel Jacobowitz wrote:
> On Tue, Apr 03, 2007 at 03:23:56PM +0200, Denis PILAT wrote:
>   
>> For the global variable declared like that
>>  int array[] = {1, 2, 3, 4};
>> the dwarf information generated by our specific compiler is missing DW_AT_type 
>> missing from DW_TAG_subrange_type.
>>
>> Usually in dwarf2 information (ie like the bellow example for gcc4 under 
>> linux), the DW_AT_type exists for subranges :
>>
>>   < 175 (0xaf) > DW_TAG_array_type
>>   | DW_AT_sibling : < 191 (0xbf) >
>>   | DW_AT_type : < 168 (0xa8) >
>>   `--------------------------
>>      < 184 (0xb8) > DW_TAG_subrange_type
>>    * | DW_AT_type : < 191 (0xbf) >*          <<<<<-------- missing from my elf 
>> file
>>      | DW_AT_upper_bound : DW_AT_upper_bound(DW_FORM_data1) : 3
>>      `--------------------------
>>     
>
> Conveniently, the DWARF 3 standard specifies what this means (DWARF 2
> may also; I didn't check).  From the standard:
>
>   
>> If the subrange entry has no type attribute describing the basis type,
>> the basis type is assumed to be the same as the object described by
>> the lower bound attribute (if it references an object). If there is no
>> lower bound attribute, or that attribute does not reference an object,
>> the basis type is the type of the upper bound or count attribute (if
>> either of them references an object). If there is no upper bound or
>> count attribute, or neither references an object, the type is assumed
>> to be the same type, in the source language of the compilation unit
>> containing the subrange entry, as a signed integer with the same size
>> as an address on the target machine.
>>     
>
> Since we do not handle objects for bounds yet, we're only interested
> in that last case.  So, we should use an integer type the size of an
> address.  Try using dwarf_base_type (DW_ATE_signed, TARGET_ADDR_BIT /
> 8, cu)?
>   
Tried, it works as well.
> That function is, in fact, very buggy.  We should fix it.  It has
> hardcoded sizes of 1, 2, 4 for char, short, int and doesn't support
> long long at all.
>   
And you want me to use it, thanks for the gift !-)

>> I'm also wondering about  the code:
>>  base_type = die_type (die, cu);
>>  if (base_type == NULL)
>>    {
>>      complaint (&symfile_complaints,
>>                _("DW_AT_type missing from DW_TAG_subrange_type"));
>>      return;
>>    }
>> It seems we'll never have (base_type == NULL). Am I right ?
>> May be it's time to remove that as well. The complaints seems to be in a better 
>> place in my patch.
>>     
>
> You're right; please do.
>   
Done
Here is the proposed patch. No regression in the testsuite for native 
linux target.

Ok for commit ?
-- 
Denis

2007-04-18  Denis Pilat  <denis.pilat@st.com>

	* dwarf2read.c (read_subrange_type): Use of DW_ATE_signed default type
	when missing from DW_TAG_subrange_type. Remove the handling of null
	return from die_type().

Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.217
diff -u -p -r1.217 dwarf2read.c
--- dwarf2read.c        11 Apr 2007 16:04:22 -0000      1.217
+++ dwarf2read.c        18 Apr 2007 12:42:20 -0000
@@ -4914,16 +4914,13 @@ read_subrange_type (struct die_info *die
     return;

   base_type = die_type (die, cu);
-  if (base_type == NULL)
+  if (TYPE_CODE (base_type) == TYPE_CODE_VOID)
     {
       complaint (&symfile_complaints,
                 _("DW_AT_type missing from DW_TAG_subrange_type"));
-      return;
+      base_type = dwarf_base_type (DW_ATE_signed, TARGET_ADDR_BIT /8, cu);
     }

-  if (TYPE_CODE (base_type) == TYPE_CODE_VOID)
-    base_type = alloc_type (NULL);
-
   if (cu->language == language_fortran)
     {
       /* FORTRAN implies a lower bound of 1, if not given.  */

Re: [RFC] DW_AT_type missing from DW_TAG_subrange_type

[Daniel Jacobowitz]

On Wed, Apr 18, 2007 at 02:51:31PM +0200, Denis PILAT wrote:
> 2007-04-18  Denis Pilat  <denis.pilat@st.com>
> 
> 	* dwarf2read.c (read_subrange_type): Use of DW_ATE_signed default type
> 	when missing from DW_TAG_subrange_type. Remove the handling of null
> 	return from die_type().

This is OK with two small changes.  First, the changelog entry should be:

	* dwarf2read.c (read_subrange_type): Use DW_ATE_signed default type
	when missing from DW_TAG_subrange_type.  Remove the handling of null
	return from die_type.

(Grammar fix, two spaces between sentences, no parentheses after the
name of a function - that's a recent change in the GNU standards, I
think)

> +      base_type = dwarf_base_type (DW_ATE_signed, TARGET_ADDR_BIT /8, cu);

And a space on each side of the "/".

Thanks!

-- 
Daniel Jacobowitz
CodeSourcery

Re: [RFC] DW_AT_type missing from DW_TAG_subrange_type

[Denis PILAT]

Daniel Jacobowitz wrote:
> On Wed, Apr 18, 2007 at 02:51:31PM +0200, Denis PILAT wrote:
>   
>> 2007-04-18  Denis Pilat  <denis.pilat@st.com>
>>
>> 	* dwarf2read.c (read_subrange_type): Use of DW_ATE_signed default type
>> 	when missing from DW_TAG_subrange_type. Remove the handling of null
>> 	return from die_type().
>>     
>
> This is OK with two small changes.  First, the changelog entry should be:
>
> 	* dwarf2read.c (read_subrange_type): Use DW_ATE_signed default type
> 	when missing from DW_TAG_subrange_type.  Remove the handling of null
> 	return from die_type.
>
> (Grammar fix, two spaces between sentences, no parentheses after the
> name of a function - that's a recent change in the GNU standards, I
> think)
>
>   
>> +      base_type = dwarf_base_type (DW_ATE_signed, TARGET_ADDR_BIT /8, cu);
>>     
>
> And a space on each side of the "/".
>
> Thanks!
>
>   
Ok, that means I did a mistake in my previous ChangeLog entry about 
target_terminal_ours ?
Can I change it as well in the same commit, removing "()" ?

Denis

Re: [RFC] DW_AT_type missing from DW_TAG_subrange_type

[Daniel Jacobowitz]

On Wed, Apr 18, 2007 at 03:06:38PM +0200, Denis PILAT wrote:
> Ok, that means I did a mistake in my previous ChangeLog entry about 
> target_terminal_ours ?
> Can I change it as well in the same commit, removing "()" ?

Yes please.

-- 
Daniel Jacobowitz
CodeSourcery

Re: [RFC] DW_AT_type missing from DW_TAG_subrange_type

[Denis PILAT]

Daniel Jacobowitz wrote:
> On Wed, Apr 18, 2007 at 03:06:38PM +0200, Denis PILAT wrote:
>   
>> Ok, that means I did a mistake in my previous ChangeLog entry about 
>> target_terminal_ours ?
>> Can I change it as well in the same commit, removing "()" ?
>>     
>
> Yes please.
>
>   
Just committed.

-- 
Denis

2007-04-18  Denis Pilat  <denis.pilat@st.com>

	* dwarf2read.c (read_subrange_type): Use DW_ATE_signed default type
	when missing from DW_TAG_subrange_type.  Remove the handling of null
	return from die_type.

Index: dwarf2read.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2read.c,v
retrieving revision 1.217
retrieving revision 1.218
diff -u -p -r1.217 -r1.218
--- dwarf2read.c        11 Apr 2007 16:04:22 -0000      1.217
+++ dwarf2read.c        18 Apr 2007 13:25:04 -0000      1.218
@@ -4914,16 +4914,13 @@ read_subrange_type (struct die_info *die
     return;

   base_type = die_type (die, cu);
-  if (base_type == NULL)
+  if (TYPE_CODE (base_type) == TYPE_CODE_VOID)
     {
       complaint (&symfile_complaints,
                 _("DW_AT_type missing from DW_TAG_subrange_type"));
-      return;
+      base_type = dwarf_base_type (DW_ATE_signed, TARGET_ADDR_BIT / 8, cu);
     }

-  if (TYPE_CODE (base_type) == TYPE_CODE_VOID)
-    base_type = alloc_type (NULL);
-
   if (cu->language == language_fortran)
     {
       /* FORTRAN implies a lower bound of 1, if not given.  */