From 70454ee70ad63c77d39768f057d722214adef658 Mon Sep 17 00:00:00 2001 From: Zoran Zaric Date: Tue, 22 Sep 2020 10:44:45 +0100 Subject: Add as_lval argument to expression evaluator There are cases where the result of the expression evaluation is expected to be in a form of a value and not location description. One place that has this requirement is dwarf_entry_parameter_to_value function, but more are expected in the future. Until now, this requirement was fulfilled by extending the evaluated expression with a DW_OP_stack_value operation at the end. New implementation, introduces a new evaluation argument instead. * dwarf2/expr.c (dwarf_expr_context::fetch_result): Add as_lval argument. (dwarf_expr_context::eval_exp): Add as_lval argument. * dwarf2/expr.h (struct dwarf_expr_context): Add as_lval argument to fetch_result and eval_exp methods. * dwarf2/frame.c (execute_stack_op): Add as_lval argument. * dwarf2/loc.c (dwarf_entry_parameter_to_value): Remove DWARF expression extension. (dwarf2_evaluate_loc_desc_full): Add as_lval argument support. (dwarf2_evaluate_loc_desc): Add as_lval argument support. (dwarf2_locexpr_baton_eval): Add as_lval argument support. --- gdb/dwarf2/expr.c | 11 ++++++++--- gdb/dwarf2/expr.h | 22 +++++++++++++++------- gdb/dwarf2/frame.c | 2 +- gdb/dwarf2/loc.c | 27 ++++++++++----------------- gdb/dwarf2/loc.h | 6 ++++-- 5 files changed, 38 insertions(+), 30 deletions(-) diff --git a/gdb/dwarf2/expr.c b/gdb/dwarf2/expr.c index 1e67ffa..9e5a356 100644 --- a/gdb/dwarf2/expr.c +++ b/gdb/dwarf2/expr.c @@ -886,7 +886,7 @@ dwarf_expr_context::push_dwarf_reg_entry_value (call_site_parameter_kind kind, value * dwarf_expr_context::fetch_result (struct type *type, struct type *subobj_type, - LONGEST subobj_offset) + LONGEST subobj_offset, bool as_lval) { value *retval = nullptr; gdbarch *arch = this->m_per_objfile->objfile->arch (); @@ -917,6 +917,11 @@ dwarf_expr_context::fetch_result (struct type *type, struct type *subobj_type, } else { + /* If AS_LVAL is false, means that the implicit conversion + from a location description to value is expected. */ + if (!as_lval) + this->m_location = DWARF_VALUE_STACK; + switch (this->m_location) { case DWARF_VALUE_REGISTER: @@ -1037,7 +1042,7 @@ dwarf_expr_context::fetch_result (struct type *type, struct type *subobj_type, /* See expr.h. */ value * -dwarf_expr_context::evaluate (const gdb_byte *addr, size_t len, +dwarf_expr_context::evaluate (const gdb_byte *addr, size_t len, bool as_lval, dwarf2_per_cu_data *per_cu, frame_info *frame, const struct property_addr_info *addr_info, struct type *type, struct type *subobj_type, @@ -1048,7 +1053,7 @@ dwarf_expr_context::evaluate (const gdb_byte *addr, size_t len, this->m_addr_info = addr_info; eval (addr, len); - return fetch_result (type, subobj_type, subobj_offset); + return fetch_result (type, subobj_type, subobj_offset, as_lval); } /* Require that TYPE be an integral type; throw an exception if not. */ diff --git a/gdb/dwarf2/expr.h b/gdb/dwarf2/expr.h index a10fbac..16c5e71 100644 --- a/gdb/dwarf2/expr.h +++ b/gdb/dwarf2/expr.h @@ -126,11 +126,17 @@ struct dwarf_expr_context void push_address (CORE_ADDR value, bool in_stack_memory); /* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU - and FRAME context. TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe - the expected struct value representation of the evaluation - result. The ADDR_INFO property can be specified to override the - range of memory addresses with the passed in buffer. */ - value *evaluate (const gdb_byte *addr, size_t len, + and FRAME context. + + AS_LVAL defines if the returned struct value is expected to be a + value (false) or a location description (true). + + TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe the expected struct + value representation of the evaluation result. + + The ADDR_INFO property can be specified to override the range of + memory addresses with the passed in buffer. */ + value *evaluate (const gdb_byte *addr, size_t len, bool as_lval, dwarf2_per_cu_data *per_cu, frame_info *frame, const struct property_addr_info *addr_info = nullptr, struct type *type = nullptr, @@ -211,9 +217,11 @@ private: /* Fetch the result of the expression evaluation in a form of a struct value, where TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET - describe the source level representation of that result. */ + describe the source level representation of that result. + AS_LVAL defines if the fetched struct value is expected to + be a value or a location description. */ value *fetch_result (struct type *type, struct type *subobj_type, - LONGEST subobj_offset); + LONGEST subobj_offset, bool as_lval); /* Return the location expression for the frame base attribute, in START and LENGTH. The result must be live until the current diff --git a/gdb/dwarf2/frame.c b/gdb/dwarf2/frame.c index ae26a88..f3d3877 100644 --- a/gdb/dwarf2/frame.c +++ b/gdb/dwarf2/frame.c @@ -233,7 +233,7 @@ execute_stack_op (const gdb_byte *exp, ULONGEST len, int addr_size, scoped_value_mark free_values; ctx.push_address (initial, initial_in_stack_memory); - value *result_val = ctx.evaluate (exp, len, nullptr, this_frame); + value *result_val = ctx.evaluate (exp, len, true, nullptr, this_frame); if (VALUE_LVAL (result_val) == lval_memory) return value_address (result_val); diff --git a/gdb/dwarf2/loc.c b/gdb/dwarf2/loc.c index d29fdcf..2322a01 100644 --- a/gdb/dwarf2/loc.c +++ b/gdb/dwarf2/loc.c @@ -50,7 +50,7 @@ static struct value *dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame, const gdb_byte *data, size_t size, dwarf2_per_cu_data *per_cu, dwarf2_per_objfile *per_objfile, - struct type *subobj_type, LONGEST subobj_byte_offset); + struct type *subobj_type, LONGEST subobj_byte_offset, bool as_lval = true); /* Until these have formal names, we define these here. ref: http://gcc.gnu.org/wiki/DebugFission @@ -1214,7 +1214,6 @@ dwarf_entry_parameter_to_value (struct call_site_parameter *parameter, dwarf2_per_objfile *per_objfile) { const gdb_byte *data_src; - gdb_byte *data; size_t size; data_src = deref_size == -1 ? parameter->value : parameter->data_value; @@ -1225,15 +1224,8 @@ dwarf_entry_parameter_to_value (struct call_site_parameter *parameter, throw_error (NO_ENTRY_VALUE_ERROR, _("Cannot resolve DW_AT_call_data_value")); - /* DW_AT_call_value is a DWARF expression, not a DWARF - location. Postprocessing of DWARF_VALUE_MEMORY would lose the type from - DWARF block. */ - data = (gdb_byte *) alloca (size + 1); - memcpy (data, data_src, size); - data[size] = DW_OP_stack_value; - - return dwarf2_evaluate_loc_desc (type, caller_frame, data, size + 1, per_cu, - per_objfile); + return dwarf2_evaluate_loc_desc (type, caller_frame, data_src, size, per_cu, + per_objfile, false); } /* VALUE must be of type lval_computed with entry_data_value_funcs. Perform @@ -1459,7 +1451,8 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame, dwarf2_per_cu_data *per_cu, dwarf2_per_objfile *per_objfile, struct type *subobj_type, - LONGEST subobj_byte_offset) + LONGEST subobj_byte_offset, + bool as_lval) { if (subobj_type == NULL) { @@ -1479,8 +1472,8 @@ dwarf2_evaluate_loc_desc_full (struct type *type, struct frame_info *frame, try { - retval = ctx.evaluate (data, size, per_cu, frame, nullptr, type, - subobj_type, subobj_byte_offset); + retval = ctx.evaluate (data, size, as_lval, per_cu, frame, nullptr, + type, subobj_type, subobj_byte_offset); } catch (const gdb_exception_error &ex) { @@ -1521,10 +1514,10 @@ struct value * dwarf2_evaluate_loc_desc (struct type *type, struct frame_info *frame, const gdb_byte *data, size_t size, dwarf2_per_cu_data *per_cu, - dwarf2_per_objfile *per_objfile) + dwarf2_per_objfile *per_objfile, bool as_lval) { return dwarf2_evaluate_loc_desc_full (type, frame, data, size, per_cu, - per_objfile, NULL, 0); + per_objfile, NULL, 0, as_lval); } /* Evaluates a dwarf expression and stores the result in VAL, @@ -1567,7 +1560,7 @@ dwarf2_locexpr_baton_eval (const struct dwarf2_locexpr_baton *dlbaton, try { result = ctx.evaluate (dlbaton->data, dlbaton->size, - per_cu, frame, addr_stack); + true, per_cu, frame, addr_stack); } catch (const gdb_exception_error &ex) { diff --git a/gdb/dwarf2/loc.h b/gdb/dwarf2/loc.h index 5d964b0..5ff061b 100644 --- a/gdb/dwarf2/loc.h +++ b/gdb/dwarf2/loc.h @@ -72,14 +72,16 @@ struct call_site_parameter *dwarf_expr_reg_to_entry_parameter /* Evaluate a location description, starting at DATA and with length SIZE, to find the current location of variable of TYPE in the context - of FRAME. */ + of FRAME. AS_LVAL defines if the resulting struct value is expected to + be a value or a location description. */ struct value *dwarf2_evaluate_loc_desc (struct type *type, struct frame_info *frame, const gdb_byte *data, size_t size, dwarf2_per_cu_data *per_cu, - dwarf2_per_objfile *per_objfile); + dwarf2_per_objfile *per_objfile, + bool as_lval = true); /* A chain of addresses that might be needed to resolve a dynamic property. */ -- cgit v1.1