gdb/ax-gdb.h

   1 /* GDB-specific functions for operating on agent expressions
   2    Copyright 1998 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #ifndef AX_GDB_H
  22 #define AX_GDB_H
  23 \f
  24
  25 /* Types and enums */
  26
  27 /* GDB stores expressions in the form of a flattened tree (struct
  28    expression), so we just walk that tree and generate agent bytecodes
  29    as we go along.
  30
  31    GDB's normal evaluation uses struct value, which contains the
  32    expression's value as well as its address or the register it came
  33    from.  The `+' operator uses the value, whereas the unary `&'
  34    operator will use the address portion.  The `=' operator will use
  35    the address or register number of its left hand side.
  36
  37    The issues are different when generating agent bytecode.  Given a
  38    variable reference expression, we should not necessarily generate
  39    code to fetch its value, because the next operator may be `=' or
  40    unary `&'.  Instead, when we recurse on a subexpression, we
  41    indicate whether we want that expression to produce an lvalue or an
  42    rvalue.  If we requested an lvalue, then the recursive call tells
  43    us whether it generated code to compute an address on the stack, or
  44    whether the lvalue lives in a register.
  45
  46    The `axs' prefix here means `agent expression, static', because
  47    this is all static analysis of the expression, i.e. analysis which
  48    doesn't depend on the contents of memory and registers.  */
  49
  50
  51 /* Different kinds of agent expression static values.  */
  52 enum axs_lvalue_kind
  53   {
  54     /* We generated code to compute the subexpression's value.
  55        Constants and arithmetic operators yield this.  */
  56     axs_rvalue,
  57
  58     /* We generated code to yield the subexpression's value's address on
  59        the top of the stack.  If the caller needs an rvalue, it should
  60        call require_rvalue to produce the rvalue from this address.  */
  61     axs_lvalue_memory,
  62
  63     /* We didn't generate any code, and the stack is undisturbed,
  64        because the subexpression's value lives in a register; u.reg is
  65        the register number.  If the caller needs an rvalue, it should
  66        call require_rvalue to produce the rvalue from this register
  67        number.  */
  68     axs_lvalue_register
  69   };
  70
  71 /* Structure describing what we got from a subexpression.  Think of
  72    this as parallel to value.h's enum lval_type, except that we're
  73    describing a value which will exist when the expression is
  74    evaluated in the future, not a value we have in our hand.  */
  75 struct axs_value
  76   {
  77     enum axs_lvalue_kind kind;  /* see above */
  78
  79     /* The type of the subexpression.  Even if lvalue == axs_lvalue_memory,
  80        this is the type of the value itself; the value on the stack is a
  81        "pointer to" an object of this type. */
  82     struct type *type;
  83
  84     union
  85       {
  86         /* if kind == axs_lvalue_register, this is the register number */
  87         int reg;
  88       }
  89     u;
  90   };
  91 \f
  92
  93 /* Translating GDB expressions into agent expressions.  */
  94
  95 /* Given a GDB expression EXPR, translate it into the agent bytecode,
  96    and return it.  FLAGS are from enum expr_to_agent_flags.  */
  97 extern struct agent_expr *expr_to_agent (struct expression *EXPR,
  98                                          struct axs_value *VALUE);
  99
 100 /* Given a GDB expression EXPR denoting an lvalue in memory, produce a
 101    string of agent bytecode which will leave its address and size on
 102    the top of stack.  Return the agent expression.  */
 103 extern struct agent_expr *expr_to_address_and_size (struct expression *EXPR);
 104
 105 /* Given a GDB expression EXPR, return bytecode to trace its value.
 106    The result will use the `trace' and `trace_quick' bytecodes to
 107    record the value of all memory touched by the expression, and leave
 108    no values on the stack.  The caller can then use the ax_reqs
 109    function to discover which registers the expression uses.  */
 110 extern struct agent_expr *gen_trace_for_expr (CORE_ADDR, struct expression *);
 111
 112 #endif /* AX_GDB_H */