Re: decl_file

[Nick Clifton <nickc at redhat dot com>]

Hi Vijay,

> Does the latest readelf display the source file information when
> dumping debug_info section ?

No.

> When I dump debug_line from a static executable using readelf, I see
> multiple File Name Table entries (one per CU) and how to map the
> "DW_AT_decl_file" attribute in the dwarf to a file in file name table ?

This is really a GDB question, but here goes.

Short answer: Use the DW_AT_stmt_list attribute to locate the associated
file table.

Long answer: From the DWARF 4 specification:

  2.14 Declaration Coordinates

  It is sometimes useful in a debugger to be able to associate 
  a declaration with its occurrence in the program source.

  Any debugging information entry representing the declaration 
  of an object, module, subprogram or type may have DW_AT_decl_file, 
  DW_AT_decl_line and DW_AT_decl_column attributes each of whose 
  value is an unsigned integer constant.

  The value of the DW_AT_decl_file attribute corresponds to a 
  file number from the line number information table for the 
  compilation unit containing the debugging information entry and
  represents the source file in which the declaration appeared 
  (see Section 6.2).

Then:

  6.2 Line Number Information

  Line number information generated for a compilation unit is 
  represented in the .debug_line section of an object file and 
  is referenced by a corresponding compilation unit debugging
  information entry (see Section 3.1.1) in the .debug_info section.

On to the next link:

  3.1.1 Normal and Partial Compilation Unit Entries

  A normal compilation unit is represented by a debugging 
  information entry with the tag DW_TAG_compile_unit. A partial
  compilation unit is represented by a debugging information 
  entry with the tag DW_TAG_partial_unit.

Scroll down to:

  4. A DW_AT_stmt_list attribute whose value is a section 
  offset to the line number information for this compilation 
  unit.

  This information is placed in a separate object file 
  section from the debugging information entries themselves.
  The value of the statement list attribute is the offset 
  in the .debug_line section of the first byte of the line 
  number information for this compilation unit (see Section 6.2).

There you go.

Cheers
  Nick