Example walking CUs(d)

Example accessing all CUs looking for specific items(d).

Example accessing all CUs looking for specific items(d).

Loops through as many CUs as needed, stops and returns once a CU provides the desired data.

Assumes certain functions you write to remember the aspect of CUs that matter to you so once found in a cu my_needed_data_exists() or some other function of yours can identify the correct record. (Possibly a DIE global offset. Remember to note if each DIE has is_info TRUE or FALSE so libdwarf can find the DIE properly.)

Depending on your goals in examining the DIE tree it may be helpful to maintain a DIE stack of active DIEs, pushing and popping as you make your way throught the DIE levels.

We assume that on a serious error we will give up (for simplicity here).

We assume the caller to examplecuhdrd() will know what to retrieve (when we return DW_DLV_OK from examplecuhdrd() and that myrecords points to a record with all the data needed by my_needed_data_exists() and recorded by myrecord_data_for_die().

*/
struct myrecords_struct *myrecords;
void myrecord_data_for_die(struct myrecords_struct *myrecords,
    Dwarf_Die d);
int  my_needed_data_exists(struct myrecords_struct *myrecords);
 
/*  Loop on DIE tree. */
static void
record_die_and_siblingsd(Dwarf_Debug dbg, Dwarf_Die in_die,
    int is_info, int in_level,
    struct myrecords_struct *myrec,
    Dwarf_Error *error)
{
    int       res = DW_DLV_OK;
    Dwarf_Die cur_die=in_die;
    Dwarf_Die child = 0;
 
    myrecord_data_for_die(myrec,in_die);
 
    /*   Loop on a list of siblings */
    for (;;) {
        Dwarf_Die sib_die = 0;
 
        /*  Depending on your goals, the in_level,
            and the DW_TAG of cur_die, you may want
            to skip the dwarf_child call. */
        res = dwarf_child(cur_die,&child,error);
        if (res == DW_DLV_ERROR) {
            printf("Error in dwarf_child , level %d \n",in_level);
            exit(EXIT_FAILURE);
        }
        if (res == DW_DLV_OK) {
            record_die_and_siblingsd(dbg,child,is_info,
                in_level+1,myrec,error);
            /* No longer need 'child' die. */
            dwarf_dealloc(dbg,child,DW_DLA_DIE);
            child = 0;
        }
        /* res == DW_DLV_NO_ENTRY or DW_DLV_OK */
        res = dwarf_siblingof_b(dbg,cur_die,is_info,&sib_die,error);
        if (res == DW_DLV_ERROR) {
            exit(EXIT_FAILURE);
        }
        if (res == DW_DLV_NO_ENTRY) {
            /* Done at this level. */
            break;
        }
        /* res == DW_DLV_OK */
        if (cur_die != in_die) {
            dwarf_dealloc(dbg,cur_die,DW_DLA_DIE);
            cur_die = 0;
        }
        cur_die = sib_die;
        myrecord_data_for_die(myrec,sib_die);
    }
    return;
}
 
/*  Assuming records properly initialized for your use. */
int examplecuhdrd(Dwarf_Debug dbg,
    struct myrecords_struct *myrec,
    Dwarf_Error *error)
{
    Dwarf_Unsigned abbrev_offset = 0;
    Dwarf_Half     address_size = 0;
    Dwarf_Half     version_stamp = 0;
    Dwarf_Half     offset_size = 0;
    Dwarf_Half     extension_size = 0;
    Dwarf_Sig8     signature;
    Dwarf_Unsigned typeoffset = 0;
    Dwarf_Unsigned next_cu_header = 0;
    Dwarf_Half     header_cu_type = 0;
    Dwarf_Bool     is_info = TRUE;
    int            res = 0;
 
    while(!my_needed_data_exists(myrec)) {
        Dwarf_Die no_die = 0;
        Dwarf_Die cu_die = 0;
        Dwarf_Unsigned cu_header_length = 0;
 
        memset(&signature,0, sizeof(signature));
        res = dwarf_next_cu_header_d(dbg,is_info,&cu_header_length,
            &version_stamp, &abbrev_offset,
            &address_size, &offset_size,
            &extension_size,&signature,
            &typeoffset, &next_cu_header,
            &header_cu_type,error);
        if (res == DW_DLV_ERROR) {
            return res;
        }
        if (res == DW_DLV_NO_ENTRY) {
            if (is_info == TRUE) {
                /*  Done with .debug_info, now check for
                    .debug_types. */
                is_info = FALSE;
                continue;
            }
            /*  No more CUs to read! Never found
                what we were looking for in either
                .debug_info or .debug_types. */
            return res;
        }
        /*  The CU will have a single sibling, a cu_die.
            It is essential to call this right after
            a call to dwarf_next_cu_header_d() because
            there is no explicit connection provided to
            dwarf_siblingof_b(), which returns a DIE
            from whatever CU was last accessed by
            dwarf_next_cu_header_d()!
            The lack of explicit connection was a
            design mistake in the API (made in 1992). */
 
        res = dwarf_siblingof_b(dbg,no_die,is_info,
            &cu_die,error);
        if (res == DW_DLV_ERROR) {
            return res;
        }
        if (res == DW_DLV_NO_ENTRY) {
            /*  Impossible */
            exit(EXIT_FAILURE);
        }
        record_die_and_siblingsd(dbg,cu_die,is_info,
            0, myrec,error);
        dwarf_dealloc_die(cu_die);
    }
    /*  Found what we looked for */
    return DW_DLV_OK;
}