FW: Unsupported feature or bug?

[Gvozdeva, Svetlana]

>  -----Original Message-----
> From:         Gvozdeva, Svetlana 
> Sent: Tuesday, September 11, 2001 4:01 PM
> To:   'address@hidden'
> Subject:      FW: Unsupported feature or bug?
>
>
>
>  -----Original Message-----
> From:         Gvozdeva, Svetlana 
> Sent: Tuesday, September 11, 2001 3:29 PM
> To:   'address@hidden'
> Subject:      Unsupported feature or bug?
>
> Hello,
> Excuse me for my English.
> I would like to ask you does GDB (GNU gdb 5.0rh-5 Red Hat Linux 7.1) support the possibility of reference from one compile unit to different compile unit?

> I have tried to use for it type of reference DW_FORM_ref_addr. I have read in DWARF document (Revision:2.1 Draft 6 (May 15, 2001))

> that DW_FORM_ref_addr provides this possibility. Is it correct?
>
> Here is interesting part of the dump of .debug_info section for my test case (after readelf):
>
>   Compilation Unit @ 0:
>    Length:        209
>    Version:       2
>    Abbrev Offset: 0
>    Pointer Size:  4
>  <0><b>: Abbrev Number: 1 (DW_TAG_compile_unit)
>      DW_AT_comp_dir    : /home/sana/bloat      
>      DW_AT_language    : 1      (ANSI C)
>      DW_AT_name        : test.c
>     ...
>  <1><b3>: Abbrev Number: 2 (DW_TAG_base_type)
>      DW_AT_byte_size   : 4     
>      DW_AT_encoding    : 4      (float)
>      DW_AT_name        : float 
>  <1><bc>: Abbrev Number: 4 (DW_TAG_variable)
>      DW_AT_decl_line   : 2     
>     DW_AT_decl_column : 8     
>      DW_AT_decl_file   : 1     
>      DW_AT_accessibility: 1     (public)
>      DW_AT_name        : var2  
>      DW_AT_type        : <#150>
>      DW_AT_location    : 5 byte block: 3 c 95 4 8       (DW_OP_addr: 804950c)
>      DW_AT_external    : 1     
>   Compilation Unit @ d5:
>    Length:        132
>    Version:       2
>    Abbrev Offset: 0
>    Pointer Size:  4
>  <0><e0>: Abbrev Number: 1 (DW_TAG_compile_unit)
>      DW_AT_comp_dir    : /home/sana/bloat      
>      DW_AT_language    : 1      (ANSI C)
>      DW_AT_name        : test.c
>      ....
>  <1><150>: Abbrev Number: 2 (DW_TAG_base_type)
>      DW_AT_byte_size   : 8     
>      DW_AT_encoding    : 4      (float)
>      DW_AT_name        : double
> 
> Here is the result of debug session for my test case:
>
> GNU gdb 5.0rh-5 Red Hat Linux 7.1
> Copyright 2001 Free Software Foundation, Inc.
> GDB is free software, covered by the GNU General Public License, and you are
> welcome to change it and/or distribute copies of it under certain conditions.
> Type "show copying" to see the conditions.
> There is absolutely no warranty for GDB.  Type "show warranty" for details.
> This GDB was configured as "i386-redhat-linux"...
> (gdb) b main
> Dwarf Error: Cannot find referent at offset 336.
> (gdb)
>
> I have found the next code in file gdb+dejagnu-20010316/gdb/dwarf2read.c:
>
> /* Read a whole compilation unit into a linked list of dies.  */
>
> struct die_info *
> read_comp_unit (char *info_ptr, bfd *abfd,
>                 const struct comp_unit_head *cu_header)
> {
>   struct die_info *first_die, *last_die, *die;
>   char *cur_ptr;
>   int nesting_level;
>
>   /* Reset die reference table; we are
>      building new ones now.  */
>   dwarf2_empty_hash_tables ();
>
> As I understood  tags for only one compile unit may be located in die_ref_table at the same time.
> That is why result of function follow_die_ref (<#150>) is NULL (I think so). And as result I have the error message from GDB (look above please).

> If I change  DW_AT_type        : <#150>  to      DW_AT_type        : <#b3>  (reference in current compile unit) then GDB work without problems.

>
> What do you think about it?
> If I am wrong can you advice me please what I should do for reference usage from one compile unit to different compile unit?

> Is this feature not implemented in described version of GDB?
> May be this feature is implemented in different GDB version? In what versions?
> If no are you going to support this feature in future? When?>
>
> Thank you.
> Good bye.
> Svetlana Gvozdeva.