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1 104 markom
/* Definitions for expressions designed to be executed on the agent
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   Copyright 1998, 2000 Free Software Foundation, Inc.
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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 2 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, write to the Free Software
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   Foundation, Inc., 59 Temple Place - Suite 330,
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   Boston, MA 02111-1307, USA.  */
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#ifndef AGENTEXPR_H
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#define AGENTEXPR_H
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/* It's sometimes useful to be able to debug programs that you can't
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   really stop for more than a fraction of a second.  To this end, the
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   user can specify a tracepoint (like a breakpoint, but you don't
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   stop at it), and specify a bunch of expressions to record the
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   values of when that tracepoint is reached.  As the program runs,
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   GDB collects the values.  At any point (possibly while values are
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   still being collected), the user can display the collected values.
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   This is used with remote debugging; we don't really support it on
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   native configurations.
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   This means that expressions are being evaluated by the remote agent,
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   which doesn't have any access to the symbol table information, and
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   needs to be small and simple.
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   The agent_expr routines and datatypes are a bytecode language
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   designed to be executed by the agent.  Agent expressions work in
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   terms of fixed-width values, operators, memory references, and
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   register references.  You can evaluate a agent expression just given
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   a bunch of memory and register values to sniff at; you don't need
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   any symbolic information like variable names, types, etc.
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   GDB translates source expressions, whose meaning depends on
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   symbolic information, into agent bytecode expressions, whose meaning
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   is independent of symbolic information.  This means the agent can
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   evaluate them on the fly without reference to data only available
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   to the host GDB.  */
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/* Agent expression data structures.  */
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/* The type of an element of the agent expression stack.
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   The bytecode operation indicates which element we should access;
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   the value itself has no typing information.  GDB generates all
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   bytecode streams, so we don't have to worry about type errors.  */
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union agent_val
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  {
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    LONGEST l;
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    DOUBLEST d;
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  };
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/* A buffer containing a agent expression.  */
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struct agent_expr
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  {
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    unsigned char *buf;
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    int len;                    /* number of characters used */
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    int size;                   /* allocated size */
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    CORE_ADDR scope;
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  };
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/* The actual values of the various bytecode operations.
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   Other independent implementations of the agent bytecode engine will
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   rely on the exact values of these enums, and may not be recompiled
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   when we change this table.  The numeric values should remain fixed
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   whenever possible.  Thus, we assign them values explicitly here (to
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   allow gaps to form safely), and the disassembly table in
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   agentexpr.h behaves like an opcode map.  If you want to see them
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   grouped logically, see doc/agentexpr.texi.  */
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enum agent_op
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  {
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    aop_float = 0x01,
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    aop_add = 0x02,
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    aop_sub = 0x03,
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    aop_mul = 0x04,
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    aop_div_signed = 0x05,
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    aop_div_unsigned = 0x06,
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    aop_rem_signed = 0x07,
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    aop_rem_unsigned = 0x08,
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    aop_lsh = 0x09,
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    aop_rsh_signed = 0x0a,
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    aop_rsh_unsigned = 0x0b,
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    aop_trace = 0x0c,
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    aop_trace_quick = 0x0d,
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    aop_log_not = 0x0e,
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    aop_bit_and = 0x0f,
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    aop_bit_or = 0x10,
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    aop_bit_xor = 0x11,
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    aop_bit_not = 0x12,
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    aop_equal = 0x13,
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    aop_less_signed = 0x14,
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    aop_less_unsigned = 0x15,
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    aop_ext = 0x16,
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    aop_ref8 = 0x17,
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    aop_ref16 = 0x18,
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    aop_ref32 = 0x19,
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    aop_ref64 = 0x1a,
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    aop_ref_float = 0x1b,
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    aop_ref_double = 0x1c,
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    aop_ref_long_double = 0x1d,
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    aop_l_to_d = 0x1e,
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    aop_d_to_l = 0x1f,
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    aop_if_goto = 0x20,
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    aop_goto = 0x21,
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    aop_const8 = 0x22,
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    aop_const16 = 0x23,
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    aop_const32 = 0x24,
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    aop_const64 = 0x25,
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    aop_reg = 0x26,
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    aop_end = 0x27,
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    aop_dup = 0x28,
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    aop_pop = 0x29,
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    aop_zero_ext = 0x2a,
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    aop_swap = 0x2b,
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    aop_trace16 = 0x30,
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    aop_last
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  };
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/* Functions for building expressions.  */
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/* Allocate a new, empty agent expression.  */
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extern struct agent_expr *new_agent_expr PARAMS ((CORE_ADDR));
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/* Free a agent expression.  */
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extern void free_agent_expr PARAMS ((struct agent_expr *));
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/* Append a simple operator OP to EXPR.  */
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extern void ax_simple PARAMS ((struct agent_expr * EXPR, enum agent_op OP));
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/* Append the floating-point prefix, for the next bytecode.  */
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#define ax_float(EXPR) (ax_simple ((EXPR), aop_float))
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/* Append a sign-extension instruction to EXPR, to extend an N-bit value.  */
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extern void ax_ext PARAMS ((struct agent_expr * EXPR, int N));
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/* Append a zero-extension instruction to EXPR, to extend an N-bit value.  */
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extern void ax_zero_ext PARAMS ((struct agent_expr * EXPR, int N));
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/* Append a trace_quick instruction to EXPR, to record N bytes.  */
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extern void ax_trace_quick PARAMS ((struct agent_expr * EXPR, int N));
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/* Append a goto op to EXPR.  OP is the actual op (must be aop_goto or
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   aop_if_goto).  We assume we don't know the target offset yet,
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   because it's probably a forward branch, so we leave space in EXPR
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   for the target, and return the offset in EXPR of that space, so we
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   can backpatch it once we do know the target offset.  Use ax_label
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   to do the backpatching.  */
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extern int ax_goto PARAMS ((struct agent_expr * EXPR, enum agent_op OP));
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/* Suppose a given call to ax_goto returns some value PATCH.  When you
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   know the offset TARGET that goto should jump to, call
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   ax_label (EXPR, PATCH, TARGET)
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   to patch TARGET into the ax_goto instruction.  */
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extern void ax_label PARAMS ((struct agent_expr * EXPR, int patch, int target));
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/* Assemble code to push a constant on the stack.  */
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extern void ax_const_l PARAMS ((struct agent_expr * EXPR, LONGEST l));
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extern void ax_const_d PARAMS ((struct agent_expr * EXPR, LONGEST d));
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/* Assemble code to push the value of register number REG on the
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   stack.  */
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extern void ax_reg PARAMS ((struct agent_expr * EXPR, int REG));
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/* Functions for printing out expressions, and otherwise debugging
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   things.  */
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/* Disassemble the expression EXPR, writing to F.  */
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extern void ax_print (struct ui_file *f, struct agent_expr * EXPR);
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/* An entry in the opcode map.  */
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struct aop_map
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  {
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    /* The name of the opcode.  Null means that this entry is not a
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       valid opcode --- a hole in the opcode space.  */
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    char *name;
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    /* All opcodes take no operands from the bytecode stream, or take
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       unsigned integers of various sizes.  If this is a positive number
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       n, then the opcode is followed by an n-byte operand, which should
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       be printed as an unsigned integer.  If this is zero, then the
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       opcode takes no operands from the bytecode stream.
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       If we get more complicated opcodes in the future, don't add other
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       magic values of this; that's a crock.  Add an `enum encoding'
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       field to this, or something like that.  */
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    int op_size;
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    /* The size of the data operated upon, in bits, for bytecodes that
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       care about that (ref and const).  Zero for all others.  */
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    int data_size;
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    /* Number of stack elements consumed, and number produced.  */
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    int consumed, produced;
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  };
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/* Map of the bytecodes, indexed by bytecode number.  */
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extern struct aop_map aop_map[];
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/* Different kinds of flaws an agent expression might have, as
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   detected by agent_reqs.  */
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enum agent_flaws
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  {
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    agent_flaw_none = 0, /* code is good */
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    /* There is an invalid instruction in the stream.  */
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    agent_flaw_bad_instruction,
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    /* There is an incomplete instruction at the end of the expression.  */
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    agent_flaw_incomplete_instruction,
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    /* agent_reqs was unable to prove that every jump target is to a
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       valid offset.  Valid offsets are within the bounds of the
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       expression, and to a valid instruction boundary.  */
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    agent_flaw_bad_jump,
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    /* agent_reqs was unable to prove to its satisfaction that, for each
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       jump target location, the stack will have the same height whether
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       that location is reached via a jump or by straight execution.  */
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    agent_flaw_height_mismatch,
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    /* agent_reqs was unable to prove that every instruction following
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       an unconditional jump was the target of some other jump.  */
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    agent_flaw_hole
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  };
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/* Structure describing the requirements of a bytecode expression.  */
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struct agent_reqs
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  {
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    /* If the following is not equal to agent_flaw_none, the rest of the
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       information in this structure is suspect.  */
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    enum agent_flaws flaw;
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    /* Number of elements left on stack at end; may be negative if expr
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       only consumes elements.  */
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    int final_height;
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    /* Maximum and minimum stack height, relative to initial height.  */
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    int max_height, min_height;
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    /* Largest `ref' or `const' opcode used, in bits.  Zero means the
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       expression has no such instructions.  */
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    int max_data_size;
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    /* Bit vector of registers used.  Register R is used iff
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       reg_mask[R / 8] & (1 << (R % 8))
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       is non-zero.  Note!  You may not assume that this bitmask is long
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       enough to hold bits for all the registers of the machine; the
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       agent expression code has no idea how many registers the machine
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       has.  However, the bitmask is reg_mask_len bytes long, so the
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       valid register numbers run from 0 to reg_mask_len * 8 - 1.
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       We're assuming eight-bit bytes.  So sue me.
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       The caller should free reg_list when done.  */
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    int reg_mask_len;
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    unsigned char *reg_mask;
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  };
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/* Given an agent expression AX, fill in an agent_reqs structure REQS
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   describing it.  */
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extern void ax_reqs PARAMS ((struct agent_expr * ax,
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                             struct agent_reqs * reqs));
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#endif /* AGENTEXPR_H */

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