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Date: Thu, 19 Apr 2007 14:23:00 -0000
From: Jerome Guitton <guitton@adacore.com>
To: gdb-patches@sources.redhat.com
Subject: [RFA] dwarf2read - empty file name table
Message-ID: <20070419141647.GA53265@adacore.com>
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I am using a third-party library which makes GDB crash; it has the
following entry in its .debug_line:

[...]
Dump of debug contents of section .debug_line:

  Length:                      35
  DWARF Version:               2
  Prologue Length:             19
  Minimum Instruction Length:  4
  Initial value of 'is_stmt':  1
  Line Base:                   -1
  Line Range:                  4
  Opcode Base:                 13
  (Pointer size:               4)

 Opcodes:
  Opcode 1 has 0 args
  Opcode 2 has 1 args
  Opcode 3 has 1 args
  Opcode 4 has 1 args
  Opcode 5 has 1 args
  Opcode 6 has 0 args
  Opcode 7 has 0 args
  Opcode 8 has 0 args
  Opcode 9 has 1 args
  Opcode 10 has 0 args
  Opcode 11 has 0 args
  Opcode 12 has 1 args

 The Directory Table is empty.

 The File Name Table is empty.

 Line Number Statements:
  Extended opcode 2: set Address to 0x10000
  Extended opcode 1: End of Sequence

[...]

Note that the file name table is empty and that no file name is
specified in the line number statements. Not sure what is the use of
such an entry, but it does not seem invalid to me. Anyway, this makes
GDB crash in dwarf2read.c (trying to read into a num file name table
at End of Sequence). The followwing patch should fix this problem.

Ok to apply?
Thanks in advance,
Jerome


2007-04-19  Jerome Guitton  <guitton@adacore.com>

        * dwarf2read.c (dwarf_decode_lines): Do not dereference file_names
        if NULL.

Index: dwarf2read.c
===================================================================
--- dwarf2read.c	(revision 6081)
+++ dwarf2read.c	(revision 6082)
@@ -6996,7 +6996,8 @@
 		{
 		case DW_LNE_end_sequence:
 		  end_sequence = 1;
-                  lh->file_names[file - 1].included_p = 1;
+                  if (lh->file_names_size)
+                    lh->file_names[file - 1].included_p = 1;
                   if (!decode_for_pst_p)
 		    record_line (current_subfile, 0, address);
 		  break;