Community
Participate
Working Groups
Created attachment 248050 [details] Test vxWorks DKM. Hi Eugene, With the attached Ada VxWorks module, there is an exception in evaluate_expression. case OP_push_object_address: if (state->args_cnt == 0) str_exception(ERR_INV_ADDRESS, "Invalid address of containing object"); I'm stopped at relative pc 0x6e0 in p.adb on line: DN (E, FP, TP); It tries to evaluate die <876> for attribute AT_upper_bound: My hypothesis is that we need support for <86b> DW_AT_data_location: 2 byte block: 97 6 in order that state->args_cnt is being set. <1><866>: Abbrev Number: 3 (DW_TAG_array_type) <867> DW_AT_name : (indirect string, offset: 0xe09): pack__s <86b> DW_AT_data_location: 2 byte block: 97 6 (DW_OP_push_object_address; DW_OP_deref) <86e> DW_AT_type : <0x85f> <872> DW_AT_sibling : <0x88a> <2><876>: Abbrev Number: 4 (DW_TAG_subrange_type) <877> DW_AT_type : <0x858> <87b> DW_AT_lower_bound : 5 byte block: 97 23 4 6 6 (DW_OP_push_object_address; DW_OP_plus_uconst: 4; DW_OP_deref; DW_OP_deref) <881> DW_AT_upper_bound : 7 byte block: 97 23 4 6 23 4 6 (DW_OP_push_object_address; DW_OP_plus_uconst: 4; DW_OP_deref; DW_OP_plus_uconst: 4; DW_OP_deref) Caller (get_object_size) comes from this die: <2><936>: Abbrev Number: 13 (DW_TAG_variable) <937> DW_AT_name : fp <93a> DW_AT_decl_file : 1 <93b> DW_AT_decl_line : 6 <93c> DW_AT_type : <0x8c4> <940> DW_AT_location : 2 byte block: 91 5c (DW_OP_fbreg: -36) Best Regards, Xavier.
Hi Eugene, I'm fighting to add AT_data_location. We're going to need that for ADA support. I'm having troubles to see where I must update the code. So far, I've been in read_and_evaluate_dwarf_object_property to add AT_data_location to get dwarf_evaluate_expression called. I've updated dwarf_evaluate_expression so State->args_cnt = 1. Since we fail in get_object_size when calling get_array_index_length (it will trigger the exception when evaluating die <876> I've added: ObjectInfo * idx = get_dwarf_children(obj); read_and_evaluate_dwarf_object_property(sym_ctx, sym_frame, obj, AT_data_location, &p); before calling get_array_index_length. I go slightly further but unfortunately dwarf_expression_obj_addr is 0. My understanding is that it should be updated by these 2 rules: <940> DW_AT_location : 2 byte block: 91 5c (DW_OP_fbreg: -36) and then by <86b> DW_AT_data_location: 2 byte block: 97 6 (DW_OP_push_object_address; DW_OP_deref) I'm having troubles understanding the big picture here and what to do. Any help, suggestion, even fix is more than welcome ! So far, I can not supply you a Linux version of this ADA test program, which would help to reproduce the issue. Many thanks, Xavier.
Created attachment 248157 [details] Linux version To reproduce on Linux.
Hi Eugene, To reproduce, unzip the Linux version. Start the agent with p.out Put a breakpoint at p Run. Break hit. Continue. Break hit. Once stopped in p.adb, line 3 step-over to line 10 DN (E, FP, TP); Open expression view and add new expression fp For fp, I have the following error: At col 2: Cannot retrieve symbol size. Invalid address of containing object. Invalid address Best Regards, Xavier.
Hi Eugene, Any update on it ? I'm trying to implement AT_data_location support but so far I still need to clarify my mind to get a better understanding of how dwarf expression support works. Any advices welcome. Best Regards, Xavier.
Hi Eugene, Thanks to your fix for https://bugs.eclipse.org/bugs/show_bug.cgi?id=450361, we can now display fp but the content is unfortunately wrong because TCF doesn't support yet AT_data_location. Best Regards, Xavier.
Hi Eugene, I'm using the Linux version (for reference about the die number). I'm trying to get a correct display of fp fields and I'm really struggling. I've added a field in ObjectInfo: ObjectInfo * data_loc; I see get_location_info being called for <8e5>, the tag variable fp. I want to add the processing of the AT_data_location from <82c> to change the address of the currently evaluated object. So far, I have hacked so when object2symbol sees object <82c>, it will setup the <8e5>'s data_loc to <82c>'s object. (I could not find a better place.... Seems called when size is retrieved for fp array) I've tried in get_location_info: if ((obj) && (obj->data_loc != NULL)) { printf ("DO THE AT_data_location INDIRECTION\n"); /* Get original address */ read_dwarf_object_property(sym_ctx, sym_frame, obj, AT_location, &v); add_dwarf_location_command(info, &v); /* And also process the indirection from AT_data_location */ read_dwarf_object_property(sym_ctx, sym_frame, obj->data_loc, AT_data_location, &v); add_dwarf_location_command(info, &v); return 0; } This doesn't change anything. Any help really appreciated. Best Regards, Xavier.
Changing get_location_info() to follow AT_data_location indirection is not a good idea, because it will break other usages of the function, like computation of variable attributes of a symbol. The best place to perform hidden indirection is expression evaluation. I have committed necessary changes. Fixed. Thanks!
Hi Eugene, Many thanks for the fix. I understand now what I've missed and I have a better view of the big picture. (but still with some fuzzy points) Thanks ! Xavier.
