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324 lines
11 KiB
C++
324 lines
11 KiB
C++
/* DWARF 2 Expression Evaluator.
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Copyright (C) 2001-2023 Free Software Foundation, Inc.
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Contributed by Daniel Berlin <dan@dberlin.org>.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#if !defined (DWARF2EXPR_H)
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#define DWARF2EXPR_H
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#include "leb128.h"
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#include "gdbtypes.h"
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struct dwarf2_per_objfile;
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/* The location of a value. */
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enum dwarf_value_location
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{
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/* The piece is in memory.
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The value on the dwarf stack is its address. */
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DWARF_VALUE_MEMORY,
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/* The piece is in a register.
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The value on the dwarf stack is the register number. */
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DWARF_VALUE_REGISTER,
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/* The piece is on the dwarf stack. */
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DWARF_VALUE_STACK,
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/* The piece is a literal. */
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DWARF_VALUE_LITERAL,
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/* The piece was optimized out. */
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DWARF_VALUE_OPTIMIZED_OUT,
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/* The piece is an implicit pointer. */
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DWARF_VALUE_IMPLICIT_POINTER
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};
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/* A piece of an object, as recorded by DW_OP_piece or DW_OP_bit_piece. */
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struct dwarf_expr_piece
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{
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enum dwarf_value_location location;
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union
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{
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struct
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{
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/* This piece's address, for DWARF_VALUE_MEMORY pieces. */
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CORE_ADDR addr;
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/* Non-zero if the piece is known to be in memory and on
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the program's stack. */
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bool in_stack_memory;
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} mem;
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/* The piece's register number, for DWARF_VALUE_REGISTER pieces. */
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int regno;
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/* The piece's literal value, for DWARF_VALUE_STACK pieces. */
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struct value *value;
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struct
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{
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/* A pointer to the data making up this piece,
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for DWARF_VALUE_LITERAL pieces. */
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const gdb_byte *data;
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/* The length of the available data. */
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ULONGEST length;
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} literal;
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/* Used for DWARF_VALUE_IMPLICIT_POINTER. */
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struct
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{
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/* The referent DIE from DW_OP_implicit_pointer. */
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sect_offset die_sect_off;
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/* The byte offset into the resulting data. */
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LONGEST offset;
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} ptr;
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} v;
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/* The length of the piece, in bits. */
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ULONGEST size;
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/* The piece offset, in bits. */
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ULONGEST offset;
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};
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/* The dwarf expression stack. */
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struct dwarf_stack_value
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{
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dwarf_stack_value (struct value *value_, int in_stack_memory_)
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: value (value_), in_stack_memory (in_stack_memory_)
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{}
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struct value *value;
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/* True if the piece is in memory and is known to be on the program's stack.
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It is always ok to set this to zero. This is used, for example, to
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optimize memory access from the target. It can vastly speed up backtraces
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on long latency connections when "set stack-cache on". */
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bool in_stack_memory;
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};
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/* The expression evaluator works with a dwarf_expr_context, describing
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its current state and its callbacks. */
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struct dwarf_expr_context
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{
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dwarf_expr_context (dwarf2_per_objfile *per_objfile,
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int addr_size);
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virtual ~dwarf_expr_context () = default;
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void push_address (CORE_ADDR value, bool in_stack_memory);
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/* Evaluate the expression at ADDR (LEN bytes long) in a given PER_CU
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and FRAME context.
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AS_LVAL defines if the returned struct value is expected to be a
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value (false) or a location description (true).
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TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET describe the expected struct
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value representation of the evaluation result.
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The ADDR_INFO property can be specified to override the range of
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memory addresses with the passed in buffer. */
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value *evaluate (const gdb_byte *addr, size_t len, bool as_lval,
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dwarf2_per_cu_data *per_cu, frame_info_ptr frame,
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const struct property_addr_info *addr_info = nullptr,
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struct type *type = nullptr,
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struct type *subobj_type = nullptr,
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LONGEST subobj_offset = 0);
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private:
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/* The stack of values. */
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std::vector<dwarf_stack_value> m_stack;
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/* Target address size in bytes. */
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int m_addr_size = 0;
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/* The current depth of dwarf expression recursion, via DW_OP_call*,
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DW_OP_fbreg, DW_OP_push_object_address, etc., and the maximum
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depth we'll tolerate before raising an error. */
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int m_recursion_depth = 0, m_max_recursion_depth = 0x100;
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/* Location of the value. */
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dwarf_value_location m_location = DWARF_VALUE_MEMORY;
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/* For DWARF_VALUE_LITERAL, the current literal value's length and
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data. For DWARF_VALUE_IMPLICIT_POINTER, LEN is the offset of the
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target DIE of sect_offset kind. */
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ULONGEST m_len = 0;
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const gdb_byte *m_data = nullptr;
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/* Initialization status of variable: Non-zero if variable has been
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initialized; zero otherwise. */
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int m_initialized = 0;
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/* A vector of pieces.
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Each time DW_OP_piece is executed, we add a new element to the
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end of this array, recording the current top of the stack, the
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current location, and the size given as the operand to
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DW_OP_piece. We then pop the top value from the stack, reset the
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location, and resume evaluation.
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The Dwarf spec doesn't say whether DW_OP_piece pops the top value
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from the stack. We do, ensuring that clients of this interface
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expecting to see a value left on the top of the stack (say, code
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evaluating frame base expressions or CFA's specified with
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DW_CFA_def_cfa_expression) will get an error if the expression
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actually marks all the values it computes as pieces.
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If an expression never uses DW_OP_piece, num_pieces will be zero.
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(It would be nice to present these cases as expressions yielding
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a single piece, so that callers need not distinguish between the
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no-DW_OP_piece and one-DW_OP_piece cases. But expressions with
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no DW_OP_piece operations have no value to place in a piece's
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'size' field; the size comes from the surrounding data. So the
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two cases need to be handled separately.) */
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std::vector<dwarf_expr_piece> m_pieces;
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/* We evaluate the expression in the context of this objfile. */
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dwarf2_per_objfile *m_per_objfile;
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/* Frame information used for the evaluation. */
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frame_info_ptr m_frame = nullptr;
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/* Compilation unit used for the evaluation. */
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dwarf2_per_cu_data *m_per_cu = nullptr;
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/* Property address info used for the evaluation. */
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const struct property_addr_info *m_addr_info = nullptr;
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void eval (const gdb_byte *addr, size_t len);
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struct type *address_type () const;
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void push (struct value *value, bool in_stack_memory);
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bool stack_empty_p () const;
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void add_piece (ULONGEST size, ULONGEST offset);
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void execute_stack_op (const gdb_byte *op_ptr, const gdb_byte *op_end);
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void pop ();
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struct value *fetch (int n);
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CORE_ADDR fetch_address (int n);
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bool fetch_in_stack_memory (int n);
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/* Fetch the result of the expression evaluation in a form of
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a struct value, where TYPE, SUBOBJ_TYPE and SUBOBJ_OFFSET
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describe the source level representation of that result.
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AS_LVAL defines if the fetched struct value is expected to
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be a value or a location description. */
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value *fetch_result (struct type *type, struct type *subobj_type,
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LONGEST subobj_offset, bool as_lval);
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/* Return the location expression for the frame base attribute, in
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START and LENGTH. The result must be live until the current
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expression evaluation is complete. */
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void get_frame_base (const gdb_byte **start, size_t *length);
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/* Return the base type given by the indicated DIE at DIE_CU_OFF.
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This can throw an exception if the DIE is invalid or does not
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represent a base type. */
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struct type *get_base_type (cu_offset die_cu_off);
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/* Execute DW_AT_location expression for the DWARF expression
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subroutine in the DIE at DIE_CU_OFF in the CU. Do not touch
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STACK while it being passed to and returned from the called DWARF
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subroutine. */
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void dwarf_call (cu_offset die_cu_off);
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/* Push on DWARF stack an entry evaluated for DW_TAG_call_site's
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parameter matching KIND and KIND_U at the caller of specified BATON.
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If DEREF_SIZE is not -1 then use DW_AT_call_data_value instead of
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DW_AT_call_value. */
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void push_dwarf_reg_entry_value (call_site_parameter_kind kind,
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call_site_parameter_u kind_u,
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int deref_size);
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/* Read LENGTH bytes at ADDR into BUF. This method also handles the
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case where a caller of the evaluator passes in some data,
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but with the address being 0. In this situation, we arrange for
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memory reads to come from the passed-in buffer. */
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void read_mem (gdb_byte *buf, CORE_ADDR addr, size_t length);
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};
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/* Return the value of register number REG (a DWARF register number),
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read as an address in a given FRAME. */
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CORE_ADDR read_addr_from_reg (frame_info_ptr frame, int reg);
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void dwarf_expr_require_composition (const gdb_byte *, const gdb_byte *,
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const char *);
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int dwarf_block_to_dwarf_reg (const gdb_byte *buf, const gdb_byte *buf_end);
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int dwarf_block_to_dwarf_reg_deref (const gdb_byte *buf,
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const gdb_byte *buf_end,
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CORE_ADDR *deref_size_return);
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int dwarf_block_to_fb_offset (const gdb_byte *buf, const gdb_byte *buf_end,
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CORE_ADDR *fb_offset_return);
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int dwarf_block_to_sp_offset (struct gdbarch *gdbarch, const gdb_byte *buf,
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const gdb_byte *buf_end,
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CORE_ADDR *sp_offset_return);
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/* Wrappers around the leb128 reader routines to simplify them for our
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purposes. */
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static inline const gdb_byte *
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gdb_read_uleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
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uint64_t *r)
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{
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size_t bytes_read = read_uleb128_to_uint64 (buf, buf_end, r);
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if (bytes_read == 0)
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return NULL;
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return buf + bytes_read;
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}
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static inline const gdb_byte *
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gdb_read_sleb128 (const gdb_byte *buf, const gdb_byte *buf_end,
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int64_t *r)
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{
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size_t bytes_read = read_sleb128_to_int64 (buf, buf_end, r);
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if (bytes_read == 0)
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return NULL;
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return buf + bytes_read;
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}
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static inline const gdb_byte *
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gdb_skip_leb128 (const gdb_byte *buf, const gdb_byte *buf_end)
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{
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size_t bytes_read = skip_leb128 (buf, buf_end);
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if (bytes_read == 0)
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return NULL;
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return buf + bytes_read;
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}
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extern const gdb_byte *safe_read_uleb128 (const gdb_byte *buf,
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const gdb_byte *buf_end,
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uint64_t *r);
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extern const gdb_byte *safe_read_sleb128 (const gdb_byte *buf,
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const gdb_byte *buf_end,
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int64_t *r);
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extern const gdb_byte *safe_skip_leb128 (const gdb_byte *buf,
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const gdb_byte *buf_end);
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#endif /* DWARF2EXPR_H */
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