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Created attachment 248283 [details] Linux executable to reproduce issue. Hi Eugene, In the attached tarball, linux.ex is the ADA Linux executable. Put a breakpoint in foo.adb:31 When on line : procedure Process (R : Record_Type) is open expression view and add 'r' I have the following error: "Invalid address of containing object". Evaluate_expression fails here: if (state->args_cnt == 0) str_exception(ERR_INV_ADDRESS, "Invalid address of containing object"); As far as I understand, we try to analyze die: <2><88a>: Abbrev Number: 20 (DW_TAG_structure_type) <88b> DW_AT_name : (indirect string, offset: 0xa83): foo__record_type <88f> DW_AT_byte_size : 11 byte block: 97 23 4 6 97 6 99 f8 3 0 0 The 99 is an OP_call4 to <3f8> + <58d> <1><975>: Abbrev Number: 27 (DW_TAG_dwarf_procedure) <976> DW_AT_location : 6 byte block: 15 0 34 1e 16 13 (DW_OP_pick: 0; DW_OP_lit4; DW_OP_mul; DW_OP_swap; DW_OP_drop) <1><97d>: Abbrev Number: 27 (DW_TAG_dwarf_procedure) <97e> DW_AT_location : 6 byte block: 15 0 34 1e 16 13 (DW_OP_pick: 0; DW_OP_lit4; DW_OP_mul; DW_OP_swap; DW_OP_drop) <1><985>: Abbrev Number: 27 (DW_TAG_dwarf_procedure) <986> DW_AT_location : 27 byte block: 15 0 99 e8 3 0 0 15 2 99 f0 3 0 0 22 23 17 c fc ff ff ff 1a 16 13 16 13 (DW_OP_pick: 0; DW_OP_call4: <0x975>; DW_OP_pick: 2; DW_OP_call4: <0x97d>; DW_OP_plus; DW_OP_plus_uconst: 23; DW_OP_const4u: 4294967292; DW_OP_and; DW_OP_swap; DW_OP_drop; DW_OP_swap; DW_OP_drop) I can't get a clear understanding of what's going on. Any explanation more than welcome ! Best Regards, Xavier.
As far as I understand, the exception if (state->args_cnt == 0) str_exception(ERR_INV_ADDRESS, "Invalid address of containing object"); seems triggered because there is no knowledge of what the currently evaluated object is. (The DW_OP_push_object_address operation pushes the address of the object currently being evaluated as part of evaluation of a user presented expression.) It is given by: <4><877>: Abbrev Number: 9 (DW_TAG_formal_parameter) <878> DW_AT_name : r <87a> DW_AT_decl_file : 1 <87b> DW_AT_decl_line : 31 <87c> DW_AT_type : <0x883> <880> DW_AT_location : 2 byte block: 91 0 (DW_OP_fbreg: 0) but <880> does not seem to be processed, at least not yet when <88f> DW_AT_byte_size is being evaluated. Is my understanding correct ? Best Regards, Xavier.
(In reply to xavier pouyollon from comment #1) > As far as I understand, the exception > if (state->args_cnt == 0) str_exception(ERR_INV_ADDRESS, > "Invalid address of containing object"); > > seems triggered because there is no knowledge of what the currently > evaluated object is. (The DW_OP_push_object_address operation pushes the > address of the object currently being evaluated as part of evaluation of a > user presented expression.) > > It is given by: > <4><877>: Abbrev Number: 9 (DW_TAG_formal_parameter) > <878> DW_AT_name : r > <87a> DW_AT_decl_file : 1 > <87b> DW_AT_decl_line : 31 > <87c> DW_AT_type : <0x883> > <880> DW_AT_location : 2 byte block: 91 0 (DW_OP_fbreg: 0) > > but <880> does not seem to be processed, at least not yet when <88f> > DW_AT_byte_size is being evaluated. > > Is my understanding correct ? > > Best Regards, > Xavier. Yes, in ADA, an attribute evaluation might need address of the related object. Simple solution is to calculate object address always, but it would slow down symbol resolution for C/C++. I have changed the code to re-evaluate attribute with address if the evaluation has returned "Invalid address of containing object". Fixed. Thanks!
Hi Eugene, Many thanks for fixing this. > Simple solution is to calculate object address always, but it would slow down symbol resolution for C/C++. I've tried to implement that but got lost. > I have changed the code to re-evaluate attribute with address if the evaluation has returned "Invalid address of containing object". As far as I understand, you call get_variable_num_prop on the following attributes : AT_byte_size and AT_upper_bound / AT_lower_bound. I'm not sure GNAT won't generate Dwarf expression on other tags... I've tried to debug linux.ex : The behaviour is wrong. When you break at foo.adb:31 and look at the structure, i3 and i2 are wrong. According to the test code, they should be 2 & 3. They have a Dwarf expression for AT_data_member_location, whereas i1 has just DW_AT_data_member_location: 8. For clarity, I'll make another bugzilla. Thanks ! Xavier.
Hi Eugene, Got this from compiler team: "GNAT may generate dwarf expressions on a few attributes, but I guess that you are mostly interested in the possible occurences of push_object_address here (e.g. constants can contains dwarf expressions, but they won't contain push_object_address, so I'll exclude them for the list. Same thing for AT_frame_base, no reason to have push_object_address there). So, as of today, here is the list of attributes where you may find this operation: * location, data_member_location, data_location; * bit_size, byte_size, bit_stride, byte_stride; * upper_bound, lower_bound. To this list, you may add vtable_elem_location: GCC uses for C++ only for now but may be useful for GNAT in the future, in order to support tagged records (= Ada "classes"). As I am on it, I'll mention also that gcc generates push_object_address in AT_string_length, AT_associated and AT_allocated in the case of Fortran 90, as exemplified by section D.2.1 of the dwarf 4 standard. A priori these would not be needed for Ada though. We may realize that we need to add other occurences later on, staying in the bounds of what the standard allows in section 7; we would try to keep you informed in that case." Best Regards, Xavier.
