re PR other/56076 (Several 64-bit libgo tests FAIL in read_line_header)

	PR other/56076
	* dwarf.c (read_line_header): Don't crash if DW_AT_comp_dir
	attribute was not seen.

From-SVN: r195478

libbacktrace/ChangeLog

+2013-01-25  Jakub Jelinek  <jakub@redhat.com>
+
+	PR other/56076
+	* dwarf.c (read_line_header): Don't crash if DW_AT_comp_dir
+	attribute was not seen.
+
 2013-01-16  Ian Lance Taylor  <iant@google.com>
 
 	* dwarf.c (struct unit): Add filename and abs_filename fields.

libbacktrace/dwarf.c

@@ -1655,7 +1655,8 @@ read_line_header (struct backtrace_state *state, struct unit *u,
 		    strnlen ((const char *) hdr_buf.buf, hdr_buf.left) + 1))
 	return 0;
       dir_index = read_uleb128 (&hdr_buf);
-      if (IS_ABSOLUTE_PATH (filename))
+      if (IS_ABSOLUTE_PATH (filename)
+	  || (dir_index == 0 && u->comp_dir == NULL))
 	hdr->filenames[i] = filename;
       else
 	{