Location/expression access

Example using DWARF2-5 loclists and loc-expressions.

Valid for DWARF2 and later DWARF.

This example simply assumes the attribute has a form which relates to location lists or location expressions. Use dwarf_get_form_class() to determine if this attribute fits. Use dwarf_get_version_of_die() to help get the data you need.

See also

dwarf_get_form_class

dwarf_get_version_of_die

Reading a location expression

*/
int example_loclistcv5(Dwarf_Attribute someattr,
    Dwarf_Error *error)
{
    Dwarf_Unsigned lcount = 0;
    Dwarf_Loc_Head_c loclist_head = 0;
    int lres = 0;
 
    lres = dwarf_get_loclist_c(someattr,&loclist_head,
        &lcount,error);
    if (lres == DW_DLV_OK) {
        Dwarf_Unsigned i = 0;
 
        /*  Before any return remember to call
            dwarf_loc_head_c_dealloc(loclist_head); */
        for (i = 0; i < lcount; ++i) {
            Dwarf_Small loclist_lkind = 0;
            Dwarf_Small lle_value = 0;
            Dwarf_Unsigned rawval1 = 0;
            Dwarf_Unsigned rawval2 = 0;
            Dwarf_Bool debug_addr_unavailable = FALSE;
            Dwarf_Addr lopc = 0;
            Dwarf_Addr hipc = 0;
            Dwarf_Unsigned loclist_expr_op_count = 0;
            Dwarf_Locdesc_c locdesc_entry = 0;
            Dwarf_Unsigned expression_offset = 0;
            Dwarf_Unsigned locdesc_offset = 0;
 
            lres = dwarf_get_locdesc_entry_d(loclist_head,
                i,
                &lle_value,
                &rawval1,&rawval2,
                &debug_addr_unavailable,
                &lopc,&hipc,
                &loclist_expr_op_count,
                &locdesc_entry,
                &loclist_lkind,
                &expression_offset,
                &locdesc_offset,
                error);
            if (lres == DW_DLV_OK) {
                Dwarf_Unsigned j = 0;
                int opres = 0;
                Dwarf_Small op = 0;
 
                for (j = 0; j < loclist_expr_op_count; ++j) {
                    Dwarf_Unsigned opd1 = 0;
                    Dwarf_Unsigned opd2 = 0;
                    Dwarf_Unsigned opd3 = 0;
                    Dwarf_Unsigned offsetforbranch = 0;
 
                    opres = dwarf_get_location_op_value_c(
                        locdesc_entry, j,&op,
                        &opd1,&opd2,&opd3,
                        &offsetforbranch,
                        error);
                    if (opres == DW_DLV_OK) {
                        /*  Do something with the operators.
                            Usually you want to use opd1,2,3
                            as appropriate. Calculations
                            involving base addresses etc
                            have already been incorporated
                            in opd1,2,3.  */
                    } else {
                        dwarf_dealloc_loc_head_c(loclist_head);
                        /*Something is wrong. */
                        return opres;
                    }
                }
            } else {
                /* Something is wrong. Do something. */
                dwarf_dealloc_loc_head_c(loclist_head);
                return lres;
            }
        }
    }
    /*  Always call dwarf_loc_head_c_dealloc()
        to free all the memory associated with loclist_head.  */
    dwarf_dealloc_loc_head_c(loclist_head);
    loclist_head = 0;
    return lres;
}