/* GDB-specific functions for operating on agent expressions Copyright 1998, 1999, 2000 Free Software Foundation, Inc. This file is part of GDB. This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ #ifndef AX_GDB_H #define AX_GDB_H struct expression; /* Types and enums */ /* GDB stores expressions in the form of a flattened tree (struct expression), so we just walk that tree and generate agent bytecodes as we go along. GDB's normal evaluation uses struct value, which contains the expression's value as well as its address or the register it came from. The `+' operator uses the value, whereas the unary `&' operator will use the address portion. The `=' operator will use the address or register number of its left hand side. The issues are different when generating agent bytecode. Given a variable reference expression, we should not necessarily generate code to fetch its value, because the next operator may be `=' or unary `&'. Instead, when we recurse on a subexpression, we indicate whether we want that expression to produce an lvalue or an rvalue. If we requested an lvalue, then the recursive call tells us whether it generated code to compute an address on the stack, or whether the lvalue lives in a register. The `axs' prefix here means `agent expression, static', because this is all static analysis of the expression, i.e. analysis which doesn't depend on the contents of memory and registers. */ /* Different kinds of agent expression static values. */ enum axs_lvalue_kind { /* We generated code to compute the subexpression's value. Constants and arithmetic operators yield this. */ axs_rvalue, /* We generated code to yield the subexpression's value's address on the top of the stack. If the caller needs an rvalue, it should call require_rvalue to produce the rvalue from this address. */ axs_lvalue_memory, /* We didn't generate any code, and the stack is undisturbed, because the subexpression's value lives in a register; u.reg is the register number. If the caller needs an rvalue, it should call require_rvalue to produce the rvalue from this register number. */ axs_lvalue_register }; /* Structure describing what we got from a subexpression. Think of this as parallel to value.h's enum lval_type, except that we're describing a value which will exist when the expression is evaluated in the future, not a value we have in our hand. */ struct axs_value { enum axs_lvalue_kind kind; /* see above */ /* The type of the subexpression. Even if lvalue == axs_lvalue_memory, this is the type of the value itself; the value on the stack is a "pointer to" an object of this type. */ struct type *type; union { /* if kind == axs_lvalue_register, this is the register number */ int reg; } u; }; /* Translating GDB expressions into agent expressions. */ /* Given a GDB expression EXPR, translate it into the agent bytecode, and return it. FLAGS are from enum expr_to_agent_flags. */ extern struct agent_expr *expr_to_agent (struct expression *EXPR, struct axs_value *VALUE); /* Given a GDB expression EXPR denoting an lvalue in memory, produce a string of agent bytecode which will leave its address and size on the top of stack. Return the agent expression. */ extern struct agent_expr *expr_to_address_and_size (struct expression *EXPR); /* Given a GDB expression EXPR, return bytecode to trace its value. The result will use the `trace' and `trace_quick' bytecodes to record the value of all memory touched by the expression, and leave no values on the stack. The caller can then use the ax_reqs function to discover which registers the expression uses. */ extern struct agent_expr *gen_trace_for_expr (CORE_ADDR, struct expression *); #endif /* AX_GDB_H */