PATCH/RFC handle missing DW_AT_comp_dir attribute

PATCH/RFC handle missing DW_AT_comp_dir attribute

[Richard Earnshaw]

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This problem was found by a colleague while using GDB with the ADS tools.

These tools do not set the DW_AT_comp_dir attribute in a compilation unit 
entry, so GDB will crash trying to reference a NULL pointer.

Regardless of whether ADS is correct not to generate this directive (the 
Dwarf spec appears not to require it to), GDB should not be falling over 
in this way.  The following patch fixes the problem:

<date>  Ian Rickards  <irickard@arm.com>

	* dwarf2.c (concat_filename): If we can't establish the directory 
	just return the filename.



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Index: dwarf2.c
===================================================================
RCS file: /cvs/src/src/bfd/dwarf2.c,v
retrieving revision 1.32
diff -p -r1.32 dwarf2.c
*** dwarf2.c	27 Jun 2002 11:51:42 -0000	1.32
--- dwarf2.c	17 Jul 2002 10:38:03 -0000
*************** concat_filename (table, file)
*** 856,868 ****
    filename = table->files[file - 1].name;
    if (IS_ABSOLUTE_PATH(filename))
      return filename;
- 
    else
      {
        char* dirname = (table->files[file - 1].dir
  		       ? table->dirs[table->files[file - 1].dir - 1]
  		       : table->comp_dir);
!       return (char*) concat (dirname, "/", filename, NULL);
      }
  }
  
--- 856,873 ----
    filename = table->files[file - 1].name;
    if (IS_ABSOLUTE_PATH(filename))
      return filename;
    else
      {
        char* dirname = (table->files[file - 1].dir
  		       ? table->dirs[table->files[file - 1].dir - 1]
  		       : table->comp_dir);
! 
!       /* Not all tools set DW_AT_comp_dir, so dirname may be unknown.  The
! 	 best we can do is return the filename part.  */
!       if (dirname == NULL)
! 	return filename;
!       else
! 	return (char*) concat (dirname, "/", filename, NULL);
      }
  }
  

Re: PATCH/RFC handle missing DW_AT_comp_dir attribute

[Alan Modra]

On Wed, Jul 17, 2002 at 11:47:02AM +0100, Richard Earnshaw wrote:
> 	* dwarf2.c (concat_filename): If we can't establish the directory 
> 	just return the filename.

OK.

-- 
Alan Modra
IBM OzLabs - Linux Technology Centre

Re: PATCH/RFC handle missing DW_AT_comp_dir attribute

[Jim Blandy]

Richard Earnshaw <rearnsha@arm.com> writes:
> This problem was found by a colleague while using GDB with the ADS tools.
> 
> These tools do not set the DW_AT_comp_dir attribute in a compilation unit 
> entry, so GDB will crash trying to reference a NULL pointer.
> 
> Regardless of whether ADS is correct not to generate this directive (the 
> Dwarf spec appears not to require it to), GDB should not be falling over 
> in this way.  The following patch fixes the problem:
> 
> <date>  Ian Rickards  <irickard@arm.com>
> 
> 	* dwarf2.c (concat_filename): If we can't establish the directory 
> 	just return the filename.

Sorry --- how does this patch fix a GDB crash?  GDB doesn't use BFD to
read debugging information.

Re: PATCH/RFC handle missing DW_AT_comp_dir attribute

[Richard Earnshaw]

> 
> Richard Earnshaw <rearnsha@arm.com> writes:
> > This problem was found by a colleague while using GDB with the ADS tools.
> > 
> > These tools do not set the DW_AT_comp_dir attribute in a compilation unit 
> > entry, so GDB will crash trying to reference a NULL pointer.

> 
> Sorry --- how does this patch fix a GDB crash?  GDB doesn't use BFD to
> read debugging information.

Ah, sorry, it was my understanding from Ian that it was in GDB.  
Apparently the problem was seen in addr2line, and rather than a crash we 
just got an empty filename (since the first argument passed to concat was 
a NULL pointer).

R.