eval.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

	case O_TRACEON:
	    traceon(p->value.trace.inst, p->value.trace.event,
		p->value.trace.actions);
	    break;

	case O_TRACEOFF:
	    traceoff(p->value.lcon);
	    break;

	default:
	    panic("eval: bad op %d", p->op);
    }
 if(debug_flag[2]) { 
	fprintf(stderr," evaluated %s \n",showoperator(p->op));
 }
           
}

/*
 * Evaluate a list of commands.
 */

public evalcmdlist(cl)
Cmdlist cl;
{
    Command c;

    foreach (Command, c, cl)
	evalcmd(c);
    endfor
}

/*
 * Push "len" bytes onto the expression stack from address "addr"
 * in the process.  If there isn't room on the stack, print an error message.
 */

public rpush(addr, len)
Address addr;
int len;
{
    if (not canpush(len)) {
	error("expression too large to evaluate");
    } else {
	chksp();
	dread(sp, addr, len);
	sp += len;
    }
}

/*
 * Check if the stack has n bytes available.
 */

public Boolean canpush(n)
Integer n;
{
    return (Boolean) (sp + n < &stack[STACKSIZE]);
}

/*
 * Push a small scalar of the given type onto the stack.
 */

public pushsmall(t, v)
Symbol t;
long v;
{
    register Integer s;

    s = size(t);
    switch (s) {
	case sizeof(char):
	    push(char, v);
	    break;

	case sizeof(short):
	    push(short, v);
	    break;

	case sizeof(long):
	    push(long, v);
	    break;

	default:
	    panic("bad size %d in popsmall", s);
    }
}

/*
 * Pop an item of the given type which is assumed to be no larger
 * than a long and return it expanded into a long.
 */

public long popsmall(t)
Symbol t;
{
    long r;

    switch (size(t)) {
	case sizeof(char):
	    r = (long) pop(char);
	    break;

	case sizeof(short):
	    r = (long) pop(short);
	    break;

	case sizeof(long):
	    r = pop(long);
	    break;

	default:
	    panic("popsmall: size is %d", size(t));
    }
    return r;
}

/*
 * Evaluate a conditional expression.
 */

public Boolean cond(p)
Node p;
{
    register Boolean b;

    if (p == nil) {
	b = true;
    } else {
	eval(p);
	b = (Boolean) pop(Boolrep);
    }
    return b;
}

/*
 * Return the address corresponding to a given tree.
 */

public Address lval(p)
Node p;
{
    if (p->op == O_RVAL) {
	eval(p->value.arg[0]);
    } else {
	eval(p);
    }
    return (Address) (pop(long));
}

/*
 * Process a trace command, translating into the appropriate events
 * and associated actions.
 */

public trace(p)
Node p;
{
    Node exp, place, cond;
    Node left;

    exp = p->value.arg[0];
    place = p->value.arg[1];
    cond = p->value.arg[2];
    if (exp == nil) {
	traceall(p->op, place, cond);
    } else if (exp->op == O_QLINE or exp->op == O_LCON) {
	traceinst(p->op, exp, cond);
    } else if (place != nil and place->op == O_QLINE) {
	traceat(p->op, exp, place, cond);
    } else {
	left = exp;
	if (left->op == O_RVAL or left->op == O_CALL) {
	    left = left->value.arg[0];
	}
	if (left->op == O_SYM and isblock(left->value.sym)) {
	    traceproc(p->op, left->value.sym, place, cond);
	} else {
	    tracedata(p->op, exp, place, cond);
	}
    }
}

/*
 * Set a breakpoint that will turn on tracing.
 */

private traceall(op, place, cond)
Operator op;
Node place;
Node cond;
{
    Symbol s;
    Node event;
    Command action;

    if (place == nil) {
	s = program;
    } else {
	s = place->value.sym;
    }
    event = build(O_EQ, build(O_SYM, procsym), build(O_SYM, s));
    action = build(O_PRINTSRCPOS,
	build(O_QLINE, nil, build(O_LCON, (op == O_TRACE) ? 1 : 0)));
    if (cond != nil) {
	action = build(O_IF, cond, buildcmdlist(action));
    }
    action = build(O_TRACEON, (op == O_TRACEI), buildcmdlist(action));
    action->value.trace.event = addevent(event, buildcmdlist(action));
    if (isstdin()) {
	printevent(action->value.trace.event);
    }
}

/*
 * Set up the appropriate breakpoint for tracing an instruction.
 */

private traceinst(op, exp, cond)
Operator op;
Node exp;
Node cond;
{
    Node event, wh;
    Command action;
    Event e;

    if (exp->op == O_LCON) {
	wh = build(O_QLINE, build(O_SCON, cursource), exp);
    } else {
	wh = exp;
    }
    if (op == O_TRACEI) {
	event = build(O_EQ, build(O_SYM, pcsym), wh);
    } else {
	event = build(O_EQ, build(O_SYM, linesym), wh);
    }
    action = build(O_PRINTSRCPOS, wh);
    if (cond) {
	action = build(O_IF, cond, buildcmdlist(action));
    }
    e = addevent(event, buildcmdlist(action));
    if (isstdin()) {
	printevent(e);
    }
}

/*
 * Set a breakpoint to print an expression at a given line or address.
 */

private traceat(op, exp, place, cond)
Operator op;
Node exp;
Node place;
Node cond;
{
    Node event;
    Command action;
    Event e;

    if (op == O_TRACEI) {
	event = build(O_EQ, build(O_SYM, pcsym), place);
    } else {
	event = build(O_EQ, build(O_SYM, linesym), place);
    }
    action = build(O_PRINTSRCPOS, exp);
    if (cond != nil) {
	action = build(O_IF, cond, buildcmdlist(action));
    }
    e = addevent(event, buildcmdlist(action));
    if (isstdin()) {
	printevent(e);
    }
}

/*
 * Construct event for tracing a procedure.
 *
 * What we want here is
 *
 * 	when $proc = p do
 *	    if <condition> then
 *	        printcall;
 *	        once $pc = $retaddr do
 *	            printrtn;
 *	        end;
 *	    end if;
 *	end;
 *
 * Note that "once" is like "when" except that the event
 * deletes itself as part of its associated action.
 */

private traceproc(op, p, place, cond)
Operator op;
Symbol p;
Node place;
Node cond;
{
    Node event;
    Command action;
    Cmdlist actionlist;
    Event e;

    action = build(O_PRINTCALL, p);
    actionlist = list_alloc();
    cmdlist_append(action, actionlist);
    event = build(O_EQ, build(O_SYM, pcsym), build(O_SYM, retaddrsym));
    action = build(O_ONCE, event, buildcmdlist(build(O_PRINTRTN, p)));
    cmdlist_append(action, actionlist);
    if (cond != nil) {
	actionlist = buildcmdlist(build(O_IF, cond, actionlist));
    }
    event = build(O_EQ, build(O_SYM, procsym), build(O_SYM, p));
    e = addevent(event, actionlist);
    if (isstdin()) {
	printevent(e);
    }
}

/*
 * Set up breakpoint for tracing data.
 */

private tracedata(op, exp, place, cond)
Operator op;
Node exp;
Node place;
Node cond;
{
    Symbol p;
    Node event;
    Command action;

    p = (place == nil) ? tcontainer(exp) : place->value.sym;
    if (p == nil) {
	p = program;
    }
    action = build(O_PRINTIFCHANGED, exp);
    if (cond != nil) {
	action = build(O_IF, cond, buildcmdlist(action));
    }
    action = build(O_TRACEON, (op == O_TRACEI), buildcmdlist(action));
    event = build(O_EQ, build(O_SYM, procsym), build(O_SYM, p));
    action->value.trace.event = addevent(event, buildcmdlist(action));
    if (isstdin()) {
	printevent(action->value.trace.event);
    }
}

/*
 * Setting and unsetting of stops.
 */

public stop(p)
Node p;
{
    Node exp, place, cond, t;
    Symbol s;
    Command action;
    Event e;

    exp = p->value.arg[0];
    place = p->value.arg[1];
    cond = p->value.arg[2];
    if (exp != nil) {
	stopvar(p->op, exp, place, cond);
    } else {
	action = build(O_STOPX);
	if (cond != nil) {
	    action = build(O_IF, cond, buildcmdlist(action));
	}
	if (place == nil or place->op == O_SYM) {
	    if (place == nil) {
		s = program;
	    } else {
		s = place->value.sym;
	    }
	    t = build(O_EQ, build(O_SYM, procsym), build(O_SYM, s));
	    if (cond != nil) {
		action = build(O_TRACEON, (p->op == O_STOPI),
		    buildcmdlist(action));
		e = addevent(t, buildcmdlist(action));
		action->value.trace.event = e;
	    } else {
		e = addevent(t, buildcmdlist(action));
	    }
	    if (isstdin()) {
		printevent(e);
	    }
	} else {
	    stopinst(p->op, place, cond, action);
	}
    }
}

private stopinst(op, place, cond, action)
Operator op;
Node place;
Node cond;
Command action;
{
    Node event;
    Event e;

    if (op == O_STOP) {
	event = build(O_EQ, build(O_SYM, linesym), place);
    } else {
	event = build(O_EQ, build(O_SYM, pcsym), place);
    }
    e = addevent(event, buildcmdlist(action));
    if (isstdin()) {
	printevent(e);
    }
}

/*
 * Implement stopping on assignment to a variable by adding it to
 * the variable list.
 */

private stopvar(op, exp, place, cond)
Operator op;
Node exp;
Node place;
Node cond;
{
    Symbol p;
    Node event;
    Command action;

    if (place == nil) {
	if (exp->op == O_LCON) {
	    p = program;
	} else {
	    p = tcontainer(exp);
	    if (p == nil) {
		p = program;
	    }
	}
    } else {
	p = place->value.sym;
    }
    action = build(O_STOPIFCHANGED, exp);
    if (cond != nil) {
	action = build(O_IF, cond, buildcmdlist(action));
    }
    action = build(O_TRACEON, (op == O_STOPI), buildcmdlist(action));
    event = build(O_EQ, build(O_SYM, procsym), build(O_SYM, p));
    action->value.trace.event = addevent(event, buildcmdlist(action));
    if (isstdin()) {
	printevent(action->value.trace.event);
    }
}

/*
 * Assign the value of an expression to a variable (or term).
 */

public assign(var, exp)
Node var;
Node exp;
{
    Address addr;
    integer varsize, expsize;
    char cvalue;
    short svalue;
    long lvalue;
    float fvalue;

    if (not compatible(var->nodetype, exp->nodetype)) {
	error("incompatible types");
    }
    addr = lval(var);
    varsize = size(var->nodetype);
    expsize = size(exp->nodetype);
    eval(exp);
    if (varsize == sizeof(float) and expsize == sizeof(double)) {
	fvalue = (float) pop(double);
	dwrite(&fvalue, addr, sizeof(fvalue));
    } else {
	if (varsize < sizeof(long)) {
	    lvalue = 0;
	    popn(expsize, &lvalue);
	    switch (varsize) {
		case sizeof(char):
		    cvalue = lvalue;
		    dwrite(&cvalue, addr, sizeof(cvalue));
		    break;

		case sizeof(short):
		    svalue = lvalue;
		    dwrite(&svalue, addr, sizeof(svalue));
		    break;

		default:
		    panic("bad size %d", varsize);
	    }
	} else {
	    if (expsize <= varsize) {
		sp -= expsize;
		dwrite(sp, addr, expsize);
	    } else {
		sp -= expsize;
		dwrite(sp, addr, varsize);
	    }
	}
    }
}

/*
 * Send some nasty mail to the current support person.
 */

public gripe()
{
    typedef Operation();
    Operation *old;
    int pid, status;
    extern int versionNumber;
    char subject[100];
    char *maintainer = "linton@berkeley";

    puts("Type control-D to end your message.  Be sure to include");
    puts("your name and the name of the file you are debugging.");
    putchar('\n');
    old = signal(SIGINT, SIG_DFL);
    sprintf(subject, "dbx (version %d) gripe", versionNumber);
    pid = back("Mail", stdin, stdout, "-s", subject, maintainer, nil);
    signal(SIGINT, SIG_IGN);
    pwait(pid, &status);
    signal(SIGINT, old);
    if (status == 0) {
	puts("Thank you.");
    } else {
	puts("\nMail not sent.");
    }
}

/*
 * Give the user some help.
 */

public help()
{
    puts("run                    - begin execution of the program");
    puts("print <exp>            - print the value of the expression");
    puts("where                  - print currently active procedures");
    puts("stop at <line>         - suspend execution at the line");
    puts("stop in <proc>         - suspend execution when <proc> is called");
    puts("cont                   - continue execution");
    puts("step                   - single step one line");
    puts("next                   - step to next line (skip over calls)");
    puts("trace <line#>          - trace execution of the line");
    puts("trace <proc>           - trace calls to the procedure");
    puts("trace <var>            - trace changes to the variable");
    puts("trace <exp> at <line#> - print <exp> when <line> is reached");
    puts("status                 - print trace/stop's in effect");
    puts("delete <number>        - remove trace or stop of given number");
    puts("call <proc>            - call a procedure in program");
    puts("whatis <name>          - print the declaration of the name");
    puts("list <line>, <line>    - list source lines");
    puts("gripe                  - send mail to the person in charge of dbx");
    puts("quit                   - exit dbx");
}

/*
 * Divert output to the given file name.
 * Cannot redirect to an existing file.
 */

private int so_fd;
private Boolean notstdout;

public setout(filename)
String filename;
{
    File f;

    f = fopen(filename, "r");
    if (f != nil) {
	fclose(f);
	error("%s: file already exists", filename);
    } else {
	so_fd = dup(1);
	close(1);
	if (creat(filename, 0666) == nil) {
	    unsetout();
	    error("can't create %s", filename);
	}
	notstdout = true;
    }
}

/*
 * Revert output to standard output.
 */

public unsetout()
{
    fflush(stdout);
    close(1);
    if (dup(so_fd) != 1) {
	panic("standard out dup failed");
    }
    close(so_fd);
    notstdout = false;
}

/*
 * Determine is standard output is currently being redirected
 * to a file (as far as we know).
 */

public Boolean isredirected()
{
    return notstdout;
}