eval.c

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/**********************************************************************

  eval.c -

  $Author: yugui $
  created at: Thu Jun 10 14:22:17 JST 1993

  Copyright (C) 1993-2007 Yukihiro Matsumoto
  Copyright (C) 2000  Network Applied Communication Laboratory, Inc.
  Copyright (C) 2000  Information-technology Promotion Agency, Japan

**********************************************************************/

#include "eval_intern.h"
#include "iseq.h"
#include "gc.h"
#include "ruby/vm.h"
#include "ruby/encoding.h"

#define numberof(array) (int)(sizeof(array) / sizeof((array)[0]))

VALUE proc_invoke(VALUE, VALUE, VALUE, VALUE);
VALUE rb_binding_new(void);
NORETURN(void rb_raise_jump(VALUE));

ID rb_frame_callee(void);
VALUE rb_eLocalJumpError;
VALUE rb_eSysStackError;

#define exception_error GET_VM()->special_exceptions[ruby_error_reenter]

#include "eval_error.c"
#include "eval_jump.c"

/* initialize ruby */

void rb_clear_trace_func(void);
void rb_thread_stop_timer_thread(void);

void rb_call_inits(void);
void Init_heap(void);
void Init_BareVM(void);

void
ruby_init(void)
{
    static int initialized = 0;
    int state;

    if (initialized)
        return;
    initialized = 1;

    ruby_init_stack((void *)&state);
    Init_BareVM();
    Init_heap();

    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        rb_call_inits();
        ruby_prog_init();
    }
    POP_TAG();

    if (state) {
        error_print();
        exit(EXIT_FAILURE);
    }
    GET_VM()->running = 1;
}

extern void rb_clear_trace_func(void);

void *
ruby_options(int argc, char **argv)
{
    int state;
    void *volatile iseq = 0;

    ruby_init_stack((void *)&iseq);
    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        SAVE_ROOT_JMPBUF(GET_THREAD(), iseq = ruby_process_options(argc, argv));
    }
    else {
        rb_clear_trace_func();
        state = error_handle(state);
        iseq = (void *)INT2FIX(state);
    }
    POP_TAG();
    return iseq;
}

static void
ruby_finalize_0(void)
{
    PUSH_TAG();
    if (EXEC_TAG() == 0) {
        rb_trap_exit();
    }
    POP_TAG();
    rb_exec_end_proc();
    rb_clear_trace_func();
}

static void
ruby_finalize_1(void)
{
    ruby_sig_finalize();
    GET_THREAD()->errinfo = Qnil;
    rb_gc_call_finalizer_at_exit();
}

void
ruby_finalize(void)
{
    ruby_finalize_0();
    ruby_finalize_1();
}

void rb_thread_stop_timer_thread(void);

int
ruby_cleanup(volatile int ex)
{
    int state;
    volatile VALUE errs[2];
    rb_thread_t *th = GET_THREAD();
    int nerr;
    void rb_threadptr_interrupt(rb_thread_t *th);
    void rb_threadptr_check_signal(rb_thread_t *mth);

    rb_threadptr_interrupt(th);
    rb_threadptr_check_signal(th);
    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        SAVE_ROOT_JMPBUF(th, { RUBY_VM_CHECK_INTS(); });
    }
    POP_TAG();

    errs[1] = th->errinfo;
    th->safe_level = 0;
    ruby_init_stack(&errs[STACK_UPPER(errs, 0, 1)]);

    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        SAVE_ROOT_JMPBUF(th, ruby_finalize_0());
    }
    POP_TAG();

    errs[0] = th->errinfo;
    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        SAVE_ROOT_JMPBUF(th, rb_thread_terminate_all());
    }
    else if (ex == 0) {
        ex = state;
    }
    th->errinfo = errs[1];
    ex = error_handle(ex);
    ruby_finalize_1();
    POP_TAG();
    rb_thread_stop_timer_thread();

    state = 0;
    for (nerr = 0; nerr < numberof(errs); ++nerr) {
        VALUE err = errs[nerr];

        if (!RTEST(err)) continue;

        /* th->errinfo contains a NODE while break'ing */
        if (TYPE(err) == T_NODE) continue;

        if (rb_obj_is_kind_of(err, rb_eSystemExit)) {
            return sysexit_status(err);
        }
        else if (rb_obj_is_kind_of(err, rb_eSignal)) {
            VALUE sig = rb_iv_get(err, "signo");
            state = NUM2INT(sig);
            break;
        }
        else if (ex == 0) {
            ex = 1;
        }
    }
    ruby_vm_destruct(GET_VM());
    if (state) ruby_default_signal(state);

#if EXIT_SUCCESS != 0 || EXIT_FAILURE != 1
    switch (ex) {
#if EXIT_SUCCESS != 0
      case 0: return EXIT_SUCCESS;
#endif
#if EXIT_FAILURE != 1
      case 1: return EXIT_FAILURE;
#endif
    }
#endif

    return ex;
}

static int
ruby_exec_internal(void *n)
{
    volatile int state;
    VALUE iseq = (VALUE)n;
    rb_thread_t *th = GET_THREAD();

    if (!n) return 0;

    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        SAVE_ROOT_JMPBUF(th, {
            th->base_block = 0;
            rb_iseq_eval_main(iseq);
        });
    }
    POP_TAG();
    return state;
}

void
ruby_stop(int ex)
{
    exit(ruby_cleanup(ex));
}

int
ruby_executable_node(void *n, int *status)
{
    VALUE v = (VALUE)n;
    int s;

    switch (v) {
      case Qtrue:  s = EXIT_SUCCESS; break;
      case Qfalse: s = EXIT_FAILURE; break;
      default:
        if (!FIXNUM_P(v)) return TRUE;
        s = FIX2INT(v);
    }
    if (status) *status = s;
    return FALSE;
}

int
ruby_run_node(void *n)
{
    int status;
    if (!ruby_executable_node(n, &status)) {
        ruby_cleanup(0);
        return status;
    }
    return ruby_cleanup(ruby_exec_node(n));
}

int
ruby_exec_node(void *n)
{
    ruby_init_stack((void *)&n);
    return ruby_exec_internal(n);
}

/*
 *  call-seq:
 *     Module.nesting    -> array
 *
 *  Returns the list of +Modules+ nested at the point of call.
 *
 *     module M1
 *       module M2
 *         $a = Module.nesting
 *       end
 *     end
 *     $a           #=> [M1::M2, M1]
 *     $a[0].name   #=> "M1::M2"
 */

static VALUE
rb_mod_nesting(void)
{
    VALUE ary = rb_ary_new();
    const NODE *cref = rb_vm_cref();

    while (cref && cref->nd_next) {
        VALUE klass = cref->nd_clss;
        if (!(cref->flags & NODE_FL_CREF_PUSHED_BY_EVAL) &&
            !NIL_P(klass)) {
            rb_ary_push(ary, klass);
        }
        cref = cref->nd_next;
    }
    return ary;
}

/*
 *  call-seq:
 *     Module.constants   -> array
 *
 *  Returns an array of the names of all constants defined in the
 *  system. This list includes the names of all modules and classes.
 *
 *     p Module.constants.sort[1..5]
 *
 *  <em>produces:</em>
 *
 *     ["ARGV", "ArgumentError", "Array", "Bignum", "Binding"]
 */

static VALUE
rb_mod_s_constants(int argc, VALUE *argv, VALUE mod)
{
    const NODE *cref = rb_vm_cref();
    VALUE klass;
    VALUE cbase = 0;
    void *data = 0;

    if (argc > 0) {
        return rb_mod_constants(argc, argv, rb_cModule);
    }

    while (cref) {
        klass = cref->nd_clss;
        if (!NIL_P(klass)) {
            data = rb_mod_const_at(cref->nd_clss, data);
            if (!cbase) {
                cbase = klass;
            }
        }
        cref = cref->nd_next;
    }

    if (cbase) {
        data = rb_mod_const_of(cbase, data);
    }
    return rb_const_list(data);
}

void
rb_frozen_class_p(VALUE klass)
{
    const char *desc = "something(?!)";

    if (OBJ_FROZEN(klass)) {
        if (FL_TEST(klass, FL_SINGLETON))
            desc = "object";
        else {
            switch (TYPE(klass)) {
              case T_MODULE:
              case T_ICLASS:
                desc = "module";
                break;
              case T_CLASS:
                desc = "class";
                break;
            }
        }
        rb_error_frozen(desc);
    }
}

NORETURN(static void rb_longjmp(int, volatile VALUE));

static void
setup_exception(rb_thread_t *th, int tag, volatile VALUE mesg)
{
    VALUE at;
    VALUE e;
    const char *file;
    volatile int line = 0;

    if (NIL_P(mesg))
        mesg = th->errinfo;
    if (NIL_P(mesg)) {
        mesg = rb_exc_new(rb_eRuntimeError, 0, 0);
    }

    file = rb_sourcefile();
    if (file) line = rb_sourceline();
    if (file && !NIL_P(mesg)) {
        if (mesg == sysstack_error) {
            at = rb_enc_sprintf(rb_usascii_encoding(), "%s:%d", file, line);
            at = rb_ary_new3(1, at);
            rb_iv_set(mesg, "bt", at);
        }
        else {
            at = get_backtrace(mesg);
            if (NIL_P(at)) {
                at = rb_make_backtrace();
                if (OBJ_FROZEN(mesg)) {
                    mesg = rb_obj_dup(mesg);
                }
                set_backtrace(mesg, at);
            }
        }
    }
    if (!NIL_P(mesg)) {
        th->errinfo = mesg;
    }

    if (RTEST(ruby_debug) && !NIL_P(e = th->errinfo) &&
        !rb_obj_is_kind_of(e, rb_eSystemExit)) {
        int status;

        PUSH_TAG();
        if ((status = EXEC_TAG()) == 0) {
            RB_GC_GUARD(e) = rb_obj_as_string(e);
            if (file && line) {
                warn_printf("Exception `%s' at %s:%d - %s\n",
                            rb_obj_classname(th->errinfo),
                            file, line, RSTRING_PTR(e));
            }
            else if (file) {
                warn_printf("Exception `%s' at %s - %s\n",
                            rb_obj_classname(th->errinfo),
                            file, RSTRING_PTR(e));
            }
            else {
                warn_printf("Exception `%s' - %s\n",
                            rb_obj_classname(th->errinfo),
                            RSTRING_PTR(e));
            }
        }
        POP_TAG();
        if (status == TAG_FATAL && th->errinfo == exception_error) {
            th->errinfo = mesg;
        }
        else if (status) {
            rb_threadptr_reset_raised(th);
            JUMP_TAG(status);
        }
    }

    if (rb_threadptr_set_raised(th)) {
        th->errinfo = exception_error;
        rb_threadptr_reset_raised(th);
        JUMP_TAG(TAG_FATAL);
    }

    rb_trap_restore_mask();

    if (tag != TAG_FATAL) {
        EXEC_EVENT_HOOK(th, RUBY_EVENT_RAISE, th->cfp->self, 0, 0);
    }
}

static void
rb_longjmp(int tag, volatile VALUE mesg)
{
    rb_thread_t *th = GET_THREAD();
    setup_exception(th, tag, mesg);
    rb_thread_raised_clear(th);
    JUMP_TAG(tag);
}

static VALUE make_exception(int argc, VALUE *argv, int isstr);

void
rb_exc_raise(VALUE mesg)
{
    if (!NIL_P(mesg)) {
        mesg = make_exception(1, &mesg, FALSE);
    }
    rb_longjmp(TAG_RAISE, mesg);
}

void
rb_exc_fatal(VALUE mesg)
{
    if (!NIL_P(mesg)) {
        mesg = make_exception(1, &mesg, FALSE);
    }
    rb_longjmp(TAG_FATAL, mesg);
}

void
rb_interrupt(void)
{
    rb_raise(rb_eInterrupt, "%s", "");
}

static VALUE get_errinfo(void);

/*
 *  call-seq:
 *     raise
 *     raise(string)
 *     raise(exception [, string [, array]])
 *     fail
 *     fail(string)
 *     fail(exception [, string [, array]])
 *
 *  With no arguments, raises the exception in <code>$!</code> or raises
 *  a <code>RuntimeError</code> if <code>$!</code> is +nil+.
 *  With a single +String+ argument, raises a
 *  +RuntimeError+ with the string as a message. Otherwise,
 *  the first parameter should be the name of an +Exception+
 *  class (or an object that returns an +Exception+ object when sent
 *  an +exception+ message). The optional second parameter sets the
 *  message associated with the exception, and the third parameter is an
 *  array of callback information. Exceptions are caught by the
 *  +rescue+ clause of <code>begin...end</code> blocks.
 *
 *     raise "Failed to create socket"
 *     raise ArgumentError, "No parameters", caller
 */

static VALUE
rb_f_raise(int argc, VALUE *argv)
{
    VALUE err;
    if (argc == 0) {
        err = get_errinfo();
        if (!NIL_P(err)) {
            argc = 1;
            argv = &err;
        }
    }
    rb_raise_jump(rb_make_exception(argc, argv));
    return Qnil;                /* not reached */
}

static VALUE
make_exception(int argc, VALUE *argv, int isstr)
{
    VALUE mesg;
    ID exception;
    int n;

    mesg = Qnil;
    switch (argc) {
      case 0:
        break;
      case 1:
        if (NIL_P(argv[0]))
            break;
        if (isstr) {
            mesg = rb_check_string_type(argv[0]);
            if (!NIL_P(mesg)) {
                mesg = rb_exc_new3(rb_eRuntimeError, mesg);
                break;
            }
        }
        n = 0;
        goto exception_call;

      case 2:
      case 3:
        n = 1;
      exception_call:
        if (argv[0] == sysstack_error) return argv[0];
        CONST_ID(exception, "exception");
        mesg = rb_check_funcall(argv[0], exception, n, argv+1);
        if (mesg == Qundef) {
            rb_raise(rb_eTypeError, "exception class/object expected");
        }
        break;
      default:
        rb_raise(rb_eArgError, "wrong number of arguments (%d for 0..3)", argc);
        break;
    }
    if (argc > 0) {
        if (!rb_obj_is_kind_of(mesg, rb_eException))
            rb_raise(rb_eTypeError, "exception object expected");
        if (argc > 2)
            set_backtrace(mesg, argv[2]);
    }

    return mesg;
}

VALUE
rb_make_exception(int argc, VALUE *argv)
{
    return make_exception(argc, argv, TRUE);
}

void
rb_raise_jump(VALUE mesg)
{
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = th->cfp;
    VALUE klass = cfp->me->klass;
    VALUE self = cfp->self;
    ID mid = cfp->me->called_id;

    th->cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(th->cfp);

    setup_exception(th, TAG_RAISE, mesg);

    EXEC_EVENT_HOOK(th, RUBY_EVENT_C_RETURN, self, mid, klass);
    rb_thread_raised_clear(th);
    JUMP_TAG(TAG_RAISE);
}

void
rb_jump_tag(int tag)
{
    JUMP_TAG(tag);
}

int
rb_block_given_p(void)
{
    rb_thread_t *th = GET_THREAD();

    if ((th->cfp->lfp[0] & 0x02) == 0 &&
        GC_GUARDED_PTR_REF(th->cfp->lfp[0])) {
        return TRUE;
    }
    else {
        return FALSE;
    }
}

int
rb_iterator_p(void)
{
    return rb_block_given_p();
}

VALUE rb_eThreadError;

void
rb_need_block(void)
{
    if (!rb_block_given_p()) {
        rb_vm_localjump_error("no block given", Qnil, 0);
    }
}

VALUE
rb_rescue2(VALUE (* b_proc) (ANYARGS), VALUE data1,
           VALUE (* r_proc) (ANYARGS), VALUE data2, ...)
{
    int state;
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = th->cfp;
    volatile VALUE result;
    volatile VALUE e_info = th->errinfo;
    va_list args;

    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
      retry_entry:
        result = (*b_proc) (data1);
    }
    else {
        th->cfp = cfp; /* restore */

        if (state == TAG_RAISE) {
            int handle = FALSE;
            VALUE eclass;

            va_init_list(args, data2);
            while ((eclass = va_arg(args, VALUE)) != 0) {
                if (rb_obj_is_kind_of(th->errinfo, eclass)) {
                    handle = TRUE;
                    break;
                }
            }
            va_end(args);

            if (handle) {
                if (r_proc) {
                    PUSH_TAG();
                    if ((state = EXEC_TAG()) == 0) {
                        result = (*r_proc) (data2, th->errinfo);
                    }
                    POP_TAG();
                    if (state == TAG_RETRY) {
                        state = 0;
                        th->errinfo = Qnil;
                        goto retry_entry;
                    }
                }
                else {
                    result = Qnil;
                    state = 0;
                }
                if (state == 0) {
                    th->errinfo = e_info;
                }
            }
        }
    }
    POP_TAG();
    if (state)
        JUMP_TAG(state);

    return result;
}

VALUE
rb_rescue(VALUE (* b_proc)(ANYARGS), VALUE data1,
          VALUE (* r_proc)(ANYARGS), VALUE data2)
{
    return rb_rescue2(b_proc, data1, r_proc, data2, rb_eStandardError,
                      (VALUE)0);
}

VALUE
rb_protect(VALUE (* proc) (VALUE), VALUE data, int * state)
{
    volatile VALUE result = Qnil;
    int status;
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = th->cfp;
    struct rb_vm_protect_tag protect_tag;
    rb_jmpbuf_t org_jmpbuf;

    protect_tag.prev = th->protect_tag;

    PUSH_TAG();
    th->protect_tag = &protect_tag;
    MEMCPY(&org_jmpbuf, &(th)->root_jmpbuf, rb_jmpbuf_t, 1);
    if ((status = EXEC_TAG()) == 0) {
        SAVE_ROOT_JMPBUF(th, result = (*proc) (data));
    }
    MEMCPY(&(th)->root_jmpbuf, &org_jmpbuf, rb_jmpbuf_t, 1);
    th->protect_tag = protect_tag.prev;
    POP_TAG();

    if (state) {
        *state = status;
    }
    if (status != 0) {
        th->cfp = cfp;
        return Qnil;
    }

    return result;
}

VALUE
rb_ensure(VALUE (*b_proc)(ANYARGS), VALUE data1, VALUE (*e_proc)(ANYARGS), VALUE data2)
{
    int state;
    volatile VALUE result = Qnil;

    PUSH_TAG();
    if ((state = EXEC_TAG()) == 0) {
        result = (*b_proc) (data1);
    }
    POP_TAG();
    /* TODO: fix me */
    /* retval = prot_tag ? prot_tag->retval : Qnil; */     /* save retval */
    (*e_proc) (data2);
    if (state)
        JUMP_TAG(state);
    return result;
}

static ID
frame_func_id(rb_control_frame_t *cfp)
{
    rb_iseq_t *iseq = cfp->iseq;
    if (!iseq) {
        return cfp->me->def->original_id;
    }
    while (iseq) {
        if (RUBY_VM_IFUNC_P(iseq)) {
            return rb_intern("<ifunc>");
        }
        if (iseq->defined_method_id) {
            return iseq->defined_method_id;
        }
        if (iseq->local_iseq == iseq) {
            break;
        }
        iseq = iseq->parent_iseq;
    }
    return 0;
}

ID
rb_frame_this_func(void)
{
    return frame_func_id(GET_THREAD()->cfp);
}

ID
rb_frame_callee(void)
{
    return frame_func_id(GET_THREAD()->cfp);
}

static ID
rb_frame_caller(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *prev_cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(th->cfp);
    /* check if prev_cfp can be accessible */
    if ((void *)(th->stack + th->stack_size) == (void *)(prev_cfp)) {
        return 0;
    }
    return frame_func_id(prev_cfp);
}

void
rb_frame_pop(void)
{
    rb_thread_t *th = GET_THREAD();
    th->cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(th->cfp);
}

/*
 *  call-seq:
 *     append_features(mod)   -> mod
 *
 *  When this module is included in another, Ruby calls
 *  <code>append_features</code> in this module, passing it the
 *  receiving module in _mod_. Ruby's default implementation is
 *  to add the constants, methods, and module variables of this module
 *  to _mod_ if this module has not already been added to
 *  _mod_ or one of its ancestors. See also <code>Module#include</code>.
 */

static VALUE
rb_mod_append_features(VALUE module, VALUE include)
{
    switch (TYPE(include)) {
      case T_CLASS:
      case T_MODULE:
        break;
      default:
        Check_Type(include, T_CLASS);
        break;
    }
    rb_include_module(include, module);

    return module;
}

/*
 *  call-seq:
 *     include(module, ...)    -> self
 *
 *  Invokes <code>Module.append_features</code> on each parameter in reverse order.
 */

static VALUE
rb_mod_include(int argc, VALUE *argv, VALUE module)
{
    int i;

    for (i = 0; i < argc; i++)
        Check_Type(argv[i], T_MODULE);
    while (argc--) {
        rb_funcall(argv[argc], rb_intern("append_features"), 1, module);
        rb_funcall(argv[argc], rb_intern("included"), 1, module);
    }
    return module;
}

void
rb_obj_call_init(VALUE obj, int argc, VALUE *argv)
{
    PASS_PASSED_BLOCK();
    rb_funcall2(obj, idInitialize, argc, argv);
}

void
rb_extend_object(VALUE obj, VALUE module)
{
    rb_include_module(rb_singleton_class(obj), module);
}

/*
 *  call-seq:
 *     extend_object(obj)    -> obj
 *
 *  Extends the specified object by adding this module's constants and
 *  methods (which are added as singleton methods). This is the callback
 *  method used by <code>Object#extend</code>.
 *
 *     module Picky
 *       def Picky.extend_object(o)
 *         if String === o
 *           puts "Can't add Picky to a String"
 *         else
 *           puts "Picky added to #{o.class}"
 *           super
 *         end
 *       end
 *     end
 *     (s = Array.new).extend Picky  # Call Object.extend
 *     (s = "quick brown fox").extend Picky
 *
 *  <em>produces:</em>
 *
 *     Picky added to Array
 *     Can't add Picky to a String
 */

static VALUE
rb_mod_extend_object(VALUE mod, VALUE obj)
{
    rb_extend_object(obj, mod);
    return obj;
}

/*
 *  call-seq:
 *     obj.extend(module, ...)    -> obj
 *
 *  Adds to _obj_ the instance methods from each module given as a
 *  parameter.
 *
 *     module Mod
 *       def hello
 *         "Hello from Mod.\n"
 *       end
 *     end
 *
 *     class Klass
 *       def hello
 *         "Hello from Klass.\n"
 *       end
 *     end
 *
 *     k = Klass.new
 *     k.hello         #=> "Hello from Klass.\n"
 *     k.extend(Mod)   #=> #<Klass:0x401b3bc8>
 *     k.hello         #=> "Hello from Mod.\n"
 */

static VALUE
rb_obj_extend(int argc, VALUE *argv, VALUE obj)
{
    int i;

    if (argc == 0) {
        rb_raise(rb_eArgError, "wrong number of arguments (at least 1)");
    }
    for (i = 0; i < argc; i++)
        Check_Type(argv[i], T_MODULE);
    while (argc--) {
        rb_funcall(argv[argc], rb_intern("extend_object"), 1, obj);
        rb_funcall(argv[argc], rb_intern("extended"), 1, obj);
    }
    return obj;
}

/*
 *  call-seq:
 *     include(module, ...)   -> self
 *
 *  Invokes <code>Module.append_features</code>
 *  on each parameter in turn. Effectively adds the methods and constants
 *  in each module to the receiver.
 */

static VALUE
top_include(int argc, VALUE *argv, VALUE self)
{
    rb_thread_t *th = GET_THREAD();

    rb_secure(4);
    if (th->top_wrapper) {
        rb_warning
            ("main#include in the wrapped load is effective only in wrapper module");
        return rb_mod_include(argc, argv, th->top_wrapper);
    }
    return rb_mod_include(argc, argv, rb_cObject);
}

VALUE rb_f_trace_var();
VALUE rb_f_untrace_var();

static VALUE *
errinfo_place(rb_thread_t *th)
{
    rb_control_frame_t *cfp = th->cfp;
    rb_control_frame_t *end_cfp = RUBY_VM_END_CONTROL_FRAME(th);

    while (RUBY_VM_VALID_CONTROL_FRAME_P(cfp, end_cfp)) {
        if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
            if (cfp->iseq->type == ISEQ_TYPE_RESCUE) {
                return &cfp->dfp[-2];
            }
            else if (cfp->iseq->type == ISEQ_TYPE_ENSURE &&
                     TYPE(cfp->dfp[-2]) != T_NODE &&
                     !FIXNUM_P(cfp->dfp[-2])) {
                return &cfp->dfp[-2];
            }
        }
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
    }
    return 0;
}

static VALUE
get_thread_errinfo(rb_thread_t *th)
{
    VALUE *ptr = errinfo_place(th);
    if (ptr) {
        return *ptr;
    }
    else {
        return th->errinfo;
    }
}

static VALUE
get_errinfo(void)
{
    return get_thread_errinfo(GET_THREAD());
}

static VALUE
errinfo_getter(ID id)
{
    return get_errinfo();
}

#if 0
static void
errinfo_setter(VALUE val, ID id, VALUE *var)
{
    if (!NIL_P(val) && !rb_obj_is_kind_of(val, rb_eException)) {
        rb_raise(rb_eTypeError, "assigning non-exception to $!");
    }
    else {
        VALUE *ptr = errinfo_place(GET_THREAD());
        if (ptr) {
            *ptr = val;
        }
        else {
            rb_raise(rb_eRuntimeError, "errinfo_setter: not in rescue clause.");
        }
    }
}
#endif

VALUE
rb_errinfo(void)
{
    rb_thread_t *th = GET_THREAD();
    return th->errinfo;
}

void
rb_set_errinfo(VALUE err)
{
    if (!NIL_P(err) && !rb_obj_is_kind_of(err, rb_eException)) {
        rb_raise(rb_eTypeError, "assigning non-exception to $!");
    }
    GET_THREAD()->errinfo = err;
}

VALUE
rb_rubylevel_errinfo(void)
{
    return get_errinfo();
}

static VALUE
errat_getter(ID id)
{
    VALUE err = get_errinfo();
    if (!NIL_P(err)) {
        return get_backtrace(err);
    }
    else {
        return Qnil;
    }
}

static void
errat_setter(VALUE val, ID id, VALUE *var)
{
    VALUE err = get_errinfo();
    if (NIL_P(err)) {
        rb_raise(rb_eArgError, "$! not set");
    }
    set_backtrace(err, val);
}

/*
 *  call-seq:
 *     __method__         -> symbol
 *     __callee__         -> symbol
 *
 *  Returns the name of the current method as a Symbol.
 *  If called outside of a method, it returns <code>nil</code>.
 *
 */

static VALUE
rb_f_method_name(void)
{
    ID fname = rb_frame_caller(); /* need *caller* ID */

    if (fname) {
        return ID2SYM(fname);
    }
    else {
        return Qnil;
    }
}

void
Init_eval(void)
{
    rb_define_virtual_variable("$@", errat_getter, errat_setter);
    rb_define_virtual_variable("$!", errinfo_getter, 0);

    rb_define_global_function("raise", rb_f_raise, -1);
    rb_define_global_function("fail", rb_f_raise, -1);

    rb_define_global_function("global_variables", rb_f_global_variables, 0);    /* in variable.c */

    rb_define_global_function("__method__", rb_f_method_name, 0);
    rb_define_global_function("__callee__", rb_f_method_name, 0);

    rb_define_private_method(rb_cModule, "append_features", rb_mod_append_features, 1);
    rb_define_private_method(rb_cModule, "extend_object", rb_mod_extend_object, 1);
    rb_define_private_method(rb_cModule, "include", rb_mod_include, -1);

    rb_undef_method(rb_cClass, "module_function");

    {
        extern void Init_vm_eval(void);
        extern void Init_eval_method(void);
        Init_vm_eval();
        Init_eval_method();
    }

    rb_define_singleton_method(rb_cModule, "nesting", rb_mod_nesting, 0);
    rb_define_singleton_method(rb_cModule, "constants", rb_mod_s_constants, -1);

    rb_define_singleton_method(rb_vm_top_self(), "include", top_include, -1);

    rb_define_method(rb_mKernel, "extend", rb_obj_extend, -1);

    rb_define_global_function("trace_var", rb_f_trace_var, -1); /* in variable.c */
    rb_define_global_function("untrace_var", rb_f_untrace_var, -1);     /* in variable.c */

    exception_error = rb_exc_new3(rb_eFatal,
                                  rb_obj_freeze(rb_str_new2("exception reentered")));
    OBJ_TAINT(exception_error);
    OBJ_FREEZE(exception_error);
}

---