objdump --debugging: problems with interpretation of dump

[Roul Oldenburger]

Hello there, hi Ian,

I am asking the list and you directly because I think you did the work.

I have problems to make the right interpretation of objdump's output in 
certain cases.

What I want to do is parse/extract structure descriptions from the
debugging information.
The executable is creating a shared memory area and puts instances of 
structure types into it. The structure might be quit deep in a sense of 
nested substructures. I want to reconstruct the tree, but also need to 
calculate offset each component has to the startaddress. So I need to 
calculate always from the top structure level.

The problem is in certain cases there is no usual description of the top 
structure.

As an example this is a description of a top structure used for a shared 
memory I can use to build the tree and calculate the offsets:
----
struct gen_siso_shared_memory_vme_env__vme_env_sm_description { /* size 
208 id 1746 */
   struct gen_siso_shared_memory_vme_env__vme_env_sm_basic_description 
/* id 1688 */ _parent; /* bitsize 256, bitpos 0 */
   struct gen_siso_shared_memory_vme_env__version_description /* id 1691 
*/ version; /* bitsize 128, bitpos 256 */
   struct gen_siso_shared_memory_vme_env__static_vme_env_sm_description 
/* id 1734 */ static; /* bitsize 544, bitpos 384 */
   struct gen_siso_shared_memory_vme_env__dynamic_vme_env_sm_description 
/* id 1737 */ dynamic; /* bitsize 736, bitpos 928 */
};
----

This is the description of another top structure ... but it's empty and 
says it is /* id 0 */
----
  struct awu_siso_shared_memory__shared_memory_description { /* id 0 */
};
----

What also can be found is the following which almost look like it should
----
struct awu_siso_shared_memory__shared_memory_description___XVE { /* size 
4 id 2712 */
   struct awu_siso_shared_memory__shared_memory_basic_description /* id 
2189 */ _parent; /* bitsize 256, bitpos 0 */
   struct awu_siso_shared_memory__version_description /* id 2192 */ 
version; /* bitsize 128, bitpos 0 */
   struct awu_siso_shared_memory__static_shared_memory_description /* id 
0 */ *static___XVL; /* bitsize 32, bitpos 0 */
   struct awu_siso_shared_memory__dynamic_shared_memory_table /* id 2706 
*/ dynamic___XVA4; /* bitsize 207264, bitpos 0 */
   struct awu_siso_shared_memory__future_description /* id 2709 */ 
future; /* bitsize 43904, bitpos 0 */
   struct awu_siso_shared_memory__data_field_description /* id 2620 */ 
data_field; /* bitsize 8647040, bitpos 0 */
   struct awu_siso_shared_memory__environment_description /* id 2694 */ 
environment; /* bitsize 28061216, bitpos 0 */
};
----


Unfortunately I don't know what the meaning of
-an id 0 description is
-the ___XVE name extension is
-the extensions (___XVL, ___XVA4) in the components names are or why 
they are presented as pointer type

Also all bitpos are 0 ...



I am probably missing something but currently I don't know why this is 
though the type declaration in the source looks different and the debug 
info should look similar to the first example.

Where can I look? Is there a document explaining these cases?


Thanks for your help

Roul