runtime.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

 * Set the current function to the given symbol.
 * We must adjust "curframe" so that subsequent operations are
 * not confused; for simplicity we simply clear it.
 */

public setcurfunc (f)
Symbol f;
{
    curfunc = f;
    curframe = nil;
}

/*
 * Set curfunc to be N up/down the stack from its current value.
 */

public up (n)
integer n;
{
    integer i;
    Symbol f;
    Frame frp;
    boolean done;

    if (not isactive(program)) {
	error("program is not active");
    } else if (curfunc == nil) {
	error("no current function");
    } else {
	i = 0;
	f = curfunc;
	if (curframe != nil) {
	    frp = curframe;
	} else {
	    frp = findframe(f);
	}
	done = false;
	do {
	    if (frp == nil) {
		done = true;
		error("not that many levels");
	    } else if (i >= n) {
		done = true;
		curfunc = f;
		curframe = &curframerec;
		*curframe = *frp;
	    } else if (f == program) {
		done = true;
		error("not that many levels");
	    } else {
		frp = nextfunc(frp, &f);
	    }
	    ++i;
	} while (not done);
    }
}

public down (n)
integer n;
{
    integer i, depth;
    register Frame frp;
    Symbol f;
    struct Frame frame;

    if (not isactive(program)) {
	error("program is not active");
    } else if (curfunc == nil) {
	error("no current function");
    } else {
	depth = 0;
	frp = &frame;
	getcurfunc(frp, &f);
	if (curframe == nil) {
	    curframe = &curframerec;
	    *curframe = *(findframe(curfunc));
	}
	while ((f != curfunc or !frameeq(frp, curframe)) and f != nil) {
	    frp = nextfunc(frp, &f);
	    ++depth;
	}
	if (f == nil or n > depth) {
	    error("not that many levels");
	} else {
	    depth -= n;
	    frp = &frame;
	    getcurfunc(frp, &f);
	    for (i = 0; i < depth; i++) {
		frp = nextfunc(frp, &f);
		assert(frp != nil);
	    }
	    curfunc = f;
	    *curframe = *frp;
	}
    }
}

/*
 * Find the entry point of a procedure or function.
 */

public findbeginning(f)
Symbol f;
{
    if (isinternal(f)) {
	f->symvalue.funcv.beginaddr += 15;
    } else {
	f->symvalue.funcv.beginaddr += 2;
    }
}

/*
 * Return the address corresponding to the first line in a function.
 */

public Address firstline(f)
Symbol f;
{
    Address addr;

    addr = codeloc(f);
    while (linelookup(addr) == 0 and addr < objsize) {
	++addr;
    }
    if (addr == objsize) {
	addr = -1;
    }
    return addr;
}

/*
 * Catcher drops strike three ...
 */

public runtofirst()
{
    Address addr;

    addr = pc;
    while (linelookup(addr) == 0 and addr < objsize) {
	++addr;
    }
    if (addr < objsize) {
	stepto(addr);
    }
}

/*
 * Return the address corresponding to the end of the program.
 *
 * We look for the entry to "exit".
 */

public Address lastaddr()
{
    register Symbol s;

    s = lookup(identname("exit", true));
    if (s == nil) {
	panic("can't find exit");
    }
    return codeloc(s);
}

/*
 * Decide if the given function is currently active.
 *
 * We avoid calls to "findframe" during a stack trace for efficiency.
 * Presumably information evaluated while walking the stack is active.
 */

public Boolean isactive(f)
Symbol f;
{
    register Boolean b;

    if (isfinished(process)) {
	b = false;
    } else {
	if (walkingstack or f == program or
	  (ismodule(f) and isactive(container(f)))) {
	    b = true;
	} else {
	    b = (Boolean) (findframe(f) != nil);
	}
    }
    return b;
}

/*
 * Evaluate a call to a procedure.
 */

public callproc(procnode, arglist)
Node procnode;
Node arglist;
{
    Symbol proc;
    Integer argc;

    if (procnode->op != O_SYM) {
	beginerrmsg();
	fprintf(stderr, "can't call \"");
	prtree(stderr, procnode);
	fprintf(stderr, "\"");
	enderrmsg();
    }
    assert(procnode->op == O_SYM);
    proc = procnode->value.sym;
    if (not isblock(proc)) {
	error("\"%s\" is not a procedure or function", symname(proc));
    }
    pushenv();
    pc = codeloc(proc);
    argc = pushargs(proc, arglist);
    beginproc(proc, argc);
    isstopped = true;
    event_once(build(O_EQ, build(O_SYM, pcsym), build(O_SYM, retaddrsym)),
	buildcmdlist(build(O_PROCRTN, proc)));
    cont(0);
    /* 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.
 */

private Integer pushargs(proc, arglist)
Symbol proc;
Node arglist;
{
    Stack *savesp;
    int argc, args_size;

    savesp = sp;
    argc = evalargs(proc, arglist);
    args_size = sp - savesp;
    setreg(STKP, reg(STKP) - args_size);
    dwrite(savesp, reg(STKP), args_size);
    sp = savesp;
    return argc;
}

/*
 * Check to see if an expression is correct for a given parameter.
 * If the given parameter is false, don't worry about type inconsistencies.
 *
 * Return whether or not it is ok.
 */

private boolean chkparam (actual, formal, chk)
Node actual;
Symbol formal;
boolean chk;
{
    boolean b;

    b = true;
    if (chk) {
	if (formal == nil) {
	    beginerrmsg();
	    fprintf(stderr, "too many parameters");
	    b = false;
	} else if (not compatible(formal->type, actual->nodetype)) {
	    beginerrmsg();
	    fprintf(stderr, "type mismatch for %s", symname(formal));
	    b = false;
	}
    }
    if (b and formal != nil and isvarparam(formal) and
	not isopenarray(formal->type) and actual->op != O_RVAL)
    {
	beginerrmsg();
	fprintf(stderr, "expected variable, found \"");
	prtree(stderr, actual);
	fprintf(stderr, "\"");
	b = false;
    }
    return b;
}

/*
 * Pass an expression to a particular parameter.
 *
 * Normally we pass either the address or value, but in some cases
 * (such as C strings) we want to copy the value onto the stack and
 * pass its address.
 */

private passparam (actual, formal)
Node actual;
Symbol formal;
{
    boolean b;
    Address addr;
    Stack *savesp;
    integer paramsize;

    if (isvarparam(formal) and not isopenarray(formal->type)) {
	addr = lval(actual->value.arg[0]);
	push(Address, addr);
    } else if (passaddr(formal, actual->nodetype)) {
	savesp = sp;
	eval(actual);
	paramsize = sp - savesp;
	setreg(STKP, reg(STKP) - paramsize);
	dwrite(savesp, reg(STKP), paramsize);
	sp = savesp;
	push(Address, reg(STKP));
	if (formal != nil and isopenarray(formal->type)) {
	    push(integer, paramsize div size(formal->type->type));
	}
    } else {
	eval(actual);
    }
}

/*
 * Evaluate an argument list left-to-right.
 */

private Integer evalargs(proc, arglist)
Symbol proc;
Node arglist;
{
    Node p, actual;
    Symbol formal;
    Stack *savesp;
    Integer count;
    boolean chk;

    savesp = sp;
    count = 0;
    formal = proc->chain;
    chk = (boolean) (not nosource(proc));
    for (p = arglist; p != nil; p = p->value.arg[1]) {
	assert(p->op == O_COMMA);
	actual = p->value.arg[0];
	if (not chkparam(actual, formal, chk)) {
	    fprintf(stderr, " in call to %s", symname(proc));
	    sp = savesp;
	    enderrmsg();
	}
	passparam(actual, formal);
	if (formal != nil) {
	    formal = formal->chain;
	}
	++count;
    }
    if (chk) {
	if (formal != nil) {
	    sp = savesp;
	    error("not enough parameters to %s", symname(proc));
	}
    }
    return count;
}

public procreturn(f)
Symbol f;
{
    flushoutput();
    putchar('\n');
    printname(stdout, f);
    printf(" returns successfully\n", symname(f));
    popenv();
    erecover();
}

/*
 * Push the current environment.
 */

private pushenv()
{
    push(Address, pc);
    push(Lineno, curline);
    push(String, cursource);
    push(Boolean, isstopped);
    push(Symbol, curfunc);
    push(Frame, curframe);
    push(struct Frame, curframerec);
    push(Word, reg(PROGCTR));
    push(Word, reg(STKP));
}

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

public popenv()
{
    register String filename;

    setreg(STKP, pop(Word));
    setreg(PROGCTR, pop(Word));
    curframerec = pop(struct Frame);
    curframe = pop(Frame);
    curfunc = pop(Symbol);
    isstopped = pop(Boolean);
    filename = pop(String);
    curline = pop(Lineno);
    pc = pop(Address);
    setsource(filename);
}

/*
 * Flush the debuggee's standard output.
 *
 * This is VERY dependent on the use of stdio.
 */

public flushoutput()
{
    register Symbol p, iob;
    register Stack *savesp;

    p = lookup(identname("fflush", true));
    while (p != nil and not isblock(p)) {
	p = p->next_sym;
    }
    if (p != nil) {
	iob = lookup(identname("_iob", true));
	if (iob != nil) {
	    pushenv();
	    pc = codeloc(p);
	    savesp = sp;
	    push(long, address(iob, nil) + sizeof(struct _iobuf));
	    setreg(STKP, reg(STKP) - sizeof(long));
	    dwrite(savesp, reg(STKP), sizeof(long));
	    sp = savesp;
	    beginproc(p, 1);
	    stepto(return_addr());
	    popenv();
	}
    }
}