usr/src/usr.bin/pascal/pdx/process/step.c

/* Copyright (c) 1982 Regents of the University of California */

static char sccsid[] = "@(#)step.c 1.1 %G%";

/*
 * Continue execution up to the next source line.
 *
 * We call "nextaddr" from the machine module to figure out
 * what the object address is that corresponds to the next source line.
 * If nextaddr returns -1, then the end of the program has been reached.
 *
 * There are two ways to define the next source line depending on what
 * is desired when a procedure or function call is encountered.  Step
 * stops at the beginning of the procedure or call; next skips over it.
 */

#include "defs.h"
#include "process.h"
#include "machine.h"
#include "breakpoint.h"
#include "source.h"
#include "mappings.h"
#include "process.rep"

#       if (isvax)
#               include "machine/vaxops.h"

                LOCAL ADDRESS getcall();
#       endif

/*
 * Stepc is what is called when the step command is given.
 * It has to play with the "isstopped" information.
 */

stepc()
{
        if (!isstopped) {
                error("can't continue execution");
        }
        isstopped = FALSE;
        dostep(FALSE);
        isstopped = TRUE;
}

next()
{
        if (!isstopped) {
                error("can't continue execution");
        }
        isstopped = FALSE;
        dostep(TRUE);
        isstopped = TRUE;
}

step()
{
        dostep(FALSE);
}

/*
 * Resume execution up to the given address.  It is assumed that
 * no breakpoints exist between the current address and the one
 * we're stepping to.  This saves us from setting all the breakpoints.
 */

stepto(addr)
ADDRESS addr;
{
        setbp(addr);
        resume();
        unsetbp(addr);
        if (!isbperr()) {
                printstatus();
        }
}

LOCAL dostep(isnext)
BOOLEAN isnext;
{
        register ADDRESS addr;
        register LINENO line;
        char *filename;

        addr = pc;
        do {
#               if (isvaxpx)
                        addr = nextaddr(addr, isnext);
#               else
                        if (isnext && (addr = getcall(addr)) != 0) {
                                stepto(addr);
                        } else {
                                pstep(process);
                                addr = process->pc;
                                pc = process->pc;
                                errnum = process->signo;
                                if (!isbperr()) {
                                        printstatus();
                                }
                        }
#               endif
                line = linelookup(addr);
        } while (line == 0 && !ss_instructions);
        stepto(addr);
        curline = line;
        filename = srcfilename(addr);
        if (filename != cursource) {
                skimsource(filename);
        }
}

# if (isvax)

/*
 * If the current address contains a call instruction, return the
 * address of the instruction where control will return.
 *
 * This function is intentionally dependent on a particular type
 * of calling sequence.
 */

LOCAL ADDRESS getcall(addr)
ADDRESS addr;
{
        VAXOP op;

        iread(&op, addr, sizeof(addr));
        if (op == O_CALLS) {
                return(addr + 7);
        } else {
                return(0);
        }
}

# endif