[rfa/dwarf] Fix a line table bug

[Daniel Jacobowitz]

Hi Elena,

I failed to copy you on this patch that I posted before Jim stepped
down.  If you have a chance, could you take a look at it sometime?
Thanks!

Meanwhile, I've added gdb.dwarf2; so now I can try to write a test case
for this.  I'll do that next week.

On Thu, Sep 23, 2004 at 03:02:12PM -0400, Daniel Jacobowitz wrote:
> I have a file whose line table looks like this (excerpted):
> 
>   Extended opcode 2: set Address to 0x10399b
>   Advance Line by 405 to 406
>   Copy
>   ...
>   Extended opcode 1: End of Sequence
> 
>   ...
>   Special opcode 232: advance Address by 16 to 0x41bd9 and Line by 3 to 307
>   Advance Line by -23 to 284
>   Special opcode 201: advance Address by 14 to 0x41be7 and Line by 0 to 284
>   Set File Name to entry 19 in the File Name Table
>   Advance Line by 33 to 317
>   Special opcode 75: advance Address by 5 to 0x41bec and Line by 0 to 317
>   Set File Name to entry 1 in the File Name Table
>   Advance Line by -27 to 290
>   Advance PC by 37 to 41c11
>   Copy
> 
> The highlights are that it covers two distinct address ranges, and that in
> the lower range it has an include file with a line in it.  The line table
> for the outer file looks OK.  For the include file, we get only one line
> record - {line 317, pc 0x41bec}.
> 
> The problem comes when we try to find the line for an intermediate PC, say
> 0x60000, which does not have debug information.  We find this symtab as the
> best match, because it's the smallest symtab including the desired address.
> We look through the line table.  We fail to find a line in the main line
> table, because it's got an appropriate End Of Sequence for this exact
> reason.  We search the next symtab with the same blockvector, and we find a
> match.
> 
> Conceptually, that series of lines ends at the next line in .debug_line,
> here at 0x41c11.  If we fill in end-of-sequence markers every time we change
> out of a subfile, then the right thing happens.  This seems like a logical
> behavior to me.
> 
> OK?  I promise to write a test case once we figure out how to test bugs that
> require specific dwarf2 input.
> 
> -- 
> Daniel Jacobowitz
> 
> 2004-09-23  Daniel Jacobowitz  <dan@debian.org>
> 
> 	* dwarf2read.c (dwarf_decode_lines): When leaving a file, mark
> 	the end of the current line.
> 
> Index: dwarf2read.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/dwarf2read.c,v
> retrieving revision 1.163
> diff -u -p -r1.163 dwarf2read.c
> --- dwarf2read.c	21 Sep 2004 15:04:41 -0000	1.163
> +++ dwarf2read.c	22 Sep 2004 23:22:56 -0000
> @@ -6274,6 +6274,7 @@ dwarf_decode_lines (struct line_header *
>    CORE_ADDR baseaddr;
>    struct objfile *objfile = cu->objfile;
>    const int decode_for_pst_p = (pst != NULL);
> +  struct subfile *last_subfile = NULL;
>  
>    baseaddr = ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
>  
> @@ -6322,6 +6323,12 @@ dwarf_decode_lines (struct line_header *
>                lh->file_names[file - 1].included_p = 1;
>                if (!decode_for_pst_p)
>                  {
> +		  if (last_subfile != current_subfile)
> +		    {
> +		      if (last_subfile)
> +			record_line (last_subfile, 0, address);
> +		      last_subfile = current_subfile;
> +		    }
>  	          /* append row to matrix using current values */
>  	          record_line (current_subfile, line, 
>  	                       check_cu_functions (address, cu));
> @@ -6376,8 +6383,16 @@ dwarf_decode_lines (struct line_header *
>  	    case DW_LNS_copy:
>                lh->file_names[file - 1].included_p = 1;
>                if (!decode_for_pst_p)
> -	        record_line (current_subfile, line, 
> -	                     check_cu_functions (address, cu));
> +		{
> +		  if (last_subfile != current_subfile)
> +		    {
> +		      if (last_subfile)
> +			record_line (last_subfile, 0, address);
> +		      last_subfile = current_subfile;
> +		    }
> +		  record_line (current_subfile, line, 
> +			       check_cu_functions (address, cu));
> +		}
>  	      basic_block = 0;
>  	      break;
>  	    case DW_LNS_advance_pc:
> @@ -6404,7 +6419,10 @@ dwarf_decode_lines (struct line_header *
>                  else
>                    dir = comp_dir;
>                  if (!decode_for_pst_p)
> -                  dwarf2_start_subfile (fe->name, dir);
> +		  {
> +		    last_subfile = current_subfile;
> +		    dwarf2_start_subfile (fe->name, dir);
> +		  }
>                }
>  	      break;
>  	    case DW_LNS_set_column:
> 

-- 
Daniel Jacobowitz