usr/src/usr.bin/pascal/pdx/runtime/callproc.c

/*-
 * Copyright (c) 1980 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char sccsid[] = "@(#)callproc.c  5.4 (Berkeley) 4/16/91";
#endif /* not lint */

/*
 * Evaluate a call to a procedure.
 *
 * This file is a botch as far as modularity is concerned.
 *
 * In fact, FIXME, it does not work on either the Vax or Tahoe
 * at this point (Sep 22, 1988).  It possibly doesn't work because
 * the ptrace interface never sets "pc" back into the interpreter's
 * program counter location.
 *
 * Due to portability changes
 * in px for ANSI C, it is now even further broken, since the operand
 * stack is no longer the system stack and since the interpreter's
 * "pc" that we see is never read by the interpreter.  We could fix
 * this, and increase the modularity, by:
 *
 *    * changing this whole module to build a string of bytecodes
 *      that would: push a series of constant parameters, then call a
 *      procedure, then take a breakpoint.
 *    * Having px allocate a place for us to do this, and pass us the
 *      address of this (otherwise unused) variable.
 *    * Creating an entry point into the px interpreter which would
 *      pick up the pc value from "*addrpc" and then enter the main loop.
 *      Currently we never pick up *addrpc for speed.
 *    * Fix the code below to use the new entry point rather than "loopaddr".
 *
 * But I suspect this code is dead enough that nobody will ever get
 * around to it.                -- gnu@toad.com, 22Sep88
 */

#include "defs.h"
#include "runtime.h"
#include "sym.h"
#include "tree.h"
#include "breakpoint.h"
#include "machine.h"
#include "process.h"
#include "source.h"
#include "frame.rep"
#include "sym/classes.h"
#include "sym/sym.rep"
#include "tree/tree.rep"
#include "process/process.rep"
#include "process/pxinfo.h"

LOCAL ADDRESS retaddr;
#ifdef tahoe
BOOLEAN didret;
#endif

/*
 * Controlling logic of procedure calling.
 * Calling a procedure before ever executing the program must
 * be special cased.
 */

callproc(procnode, arglist)
NODE *procnode;
NODE *arglist;
{
        register SYM *proc;
#ifdef tahoe
        register int tmpsp, tmptmp;
        extern BOOLEAN shouldrestart;

        if (shouldrestart) {
                initstart();
        }
#endif
        if (pc == 0) {
                curline = firstline(program);
                setbp(curline);
                resume();
                unsetbp(curline);
        }
        proc = procnode->nameval;
        if (!isblock(proc)) {
                error("\"%s\" is not a procedure or function", proc->symbol);
        }
#ifdef tahoe
        doret(process);
        tmpsp = process->sp;
#endif
        pushargs(proc, arglist);
#ifdef tahoe
        tmptmp = tmpsp;
        tmpsp = process->sp;
        process->sp = tmptmp;
#endif
        pushenv(proc->symvalue.funcv.codeloc);
#ifdef tahoe
        process->sp = tmpsp;
#endif
        pushframe(proc->blkno);
        execute(proc);
        /* NOTREACHED */
}

/*
 * Push the arguments on the process' stack.  We do this by first
 * evaluating them on the "eval" stack, then copying into the process'
 * space.
 */

LOCAL pushargs(proc, arglist)
SYM *proc;
NODE *arglist;
{
        STACK *savesp;
        int args_size;

        savesp = sp;
#ifdef tahoe
        /*
         * evalargs hopefully keeps stack aligned, so we won't bother
         * aligning it afterwards, neither will we align process->sp
         * after subtracting args_size.
         */
#endif
        evalargs(proc->symbol, proc->chain, arglist);
        args_size = sp - savesp;
        process->sp -= args_size;
        dwrite(savesp, process->sp, args_size);
        sp = savesp;
}

/*
 * Evaluate arguments right-to-left because the eval stack
 * grows up, px's stack grows down.
 */

LOCAL evalargs(procname, arg, explist)
char *procname;
SYM *arg;
NODE *explist;
{
        NODE *exp;
        STACK *savesp;
        ADDRESS addr;

        if (arg == NIL) {
                if (explist != NIL) {
                        error("too many parameters to \"%s\"", procname);
                }
        } else if (explist == NIL) {
                error("not enough parameters to \"%s\"", procname);
        } else {
                if (explist->op != O_COMMA) {
                        panic("evalargs: arglist missing comma");
                }
                savesp = sp;
                evalargs(procname, arg->chain, explist->right);
                exp = explist->left;
                if (!compatible(arg->type, exp->nodetype)) {
                        sp = savesp;
                        trerror("%t is not the same type as parameter \"%s\"",
                                exp, arg->symbol);
                }
                if (arg->class == REF) {
                        if (exp->op != O_RVAL) {
                                sp = savesp;
                                error("variable expected for parameter \"%s\"", arg->symbol);
                        }
                        addr = lval(exp->left);
                        push(ADDRESS, addr);
                } else {
                        eval(exp);
                }
        }
}

/*
 * Simulate a CALL instruction by pushing the appropriate
 * stack frame information.
 *
 * Massage register 10 or 11 appropriately since it contains the
 * stack frame pointer.
 */

LOCAL pushframe(b)
int b;
{
        ADDRESS *newdp;
        FRAME callframe;

        retaddr = program->symvalue.funcv.codeloc;

/*
 * This stuff is set by the callee, just here to take up space.
 */
        callframe.stackref = 0;
        callframe.file = 0;
        callframe.blockp = 0;
        callframe.save_loc = NIL;
        callframe.save_disp = NIL;

/*
 * This is the useful stuff.
 */
        callframe.save_dp = curdp();
        callframe.save_pc = retaddr + ENDOFF;
        callframe.save_lino = 0;
        newdp = DISPLAY + (2 * b);
        dwrite(&newdp, DP, sizeof(newdp));
        process->sp -= sizeof(callframe);
        dwrite(&callframe, process->sp, sizeof(callframe));
#ifdef tahoe
        process->reg[11] = process->sp;
#else
        process->reg[10] = process->sp;
#endif
}

/*
 * Execute the procedure.  This routine does NOT return because it
 * calls "cont", which doesn't return.  We set a CALLPROC breakpoint
 * at "retaddr", the address where the called routine will return.
 *
 * The action for a CALLPROC is to call "procreturn" where we restore
 * the environment.
 */

LOCAL execute(f)
SYM *f;
{
        isstopped = TRUE;
        addbp(retaddr, CALLPROC, f, NIL, NIL, 0);
        cont();
        /* NOTREACHED */
}

procreturn(f)
SYM *f;
{
        int len;

#ifdef tahoe
        doret(process);
#endif
        printf("%s returns ", f->symbol);
        if (f->class == FUNC) {
                len = size(f->type);
                dread(sp, process->sp, len);
#ifdef tahoe
                len = (len + 3) & ~3;
#endif
                sp += len;
                printval(f->type);
                putchar('\n');
        } else {
                printf("successfully\n");
        }
        popenv();
}

/*
 * Push the current environment.
 *
 * This involves both saving pdx and interpreter values.
 * LOOPADDR is the address of the main interpreter loop.
 */

LOCAL pushenv(newpc)
ADDRESS newpc;
{
#ifdef tahoe
        /* this should be done somewhere else, but... */
        INTFP = process->fp;
#endif
        push(ADDRESS, pc);
        push(LINENO, curline);
        push(char *, cursource);
        push(BOOLEAN, isstopped);
        push(SYM *, curfunc);
        push(WORD, process->pc);
        push(WORD, process->sp);
        process->pc = LOOPADDR;
        pc = newpc;
#ifdef tahoe
        process->reg[12] = pc + ENDOFF;
#else
        process->reg[11] = pc + ENDOFF;
#endif
}

/*
 * Pop back to the real world.
 */

popenv()
{
        register PROCESS *p;
        char *filename;

        p = process;
        p->sp = pop(WORD);
        p->pc = pop(WORD);
        curfunc = pop(SYM *);
        isstopped = pop(BOOLEAN);
        filename = pop(char *);
        curline = pop(LINENO);
        pc = pop(ADDRESS);
#ifdef tahoe
        p->reg[12] = pc + 1 + ENDOFF;
#endif
        if (filename != cursource) {
                skimsource(filename);
        }
}