vm.c

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

  vm.c -

  $Author: usa $

  Copyright (C) 2004-2007 Koichi Sasada

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

#include "ruby/ruby.h"
#include "ruby/vm.h"
#include "ruby/st.h"
#include "ruby/encoding.h"
#include "internal.h"

#include "gc.h"
#include "vm_core.h"
#include "iseq.h"
#include "eval_intern.h"

#include "vm_insnhelper.h"
#include "vm_insnhelper.c"
#include "vm_exec.h"
#include "vm_exec.c"

#include "vm_method.c"
#include "vm_eval.c"

#include <assert.h>

#define BUFSIZE 0x100
#define PROCDEBUG 0

VALUE rb_cRubyVM;
VALUE rb_cThread;
VALUE rb_cEnv;
VALUE rb_mRubyVMFrozenCore;

VALUE ruby_vm_const_missing_count = 0;

char ruby_vm_redefined_flag[BOP_LAST_];

rb_thread_t *ruby_current_thread = 0;
rb_vm_t *ruby_current_vm = 0;

static void thread_free(void *ptr);

void vm_analysis_operand(int insn, int n, VALUE op);
void vm_analysis_register(int reg, int isset);
void vm_analysis_insn(int insn);

/*
 * TODO: replace with better interface at the next release.
 *
 * these functions are exported just as a workaround for ruby-debug
 * for the time being.
 */
RUBY_FUNC_EXPORTED VALUE rb_vm_make_env_object(rb_thread_t *th, rb_control_frame_t *cfp);
RUBY_FUNC_EXPORTED int rb_vm_get_sourceline(const rb_control_frame_t *cfp);

void
rb_vm_change_state(void)
{
    INC_VM_STATE_VERSION();
}

static void vm_clear_global_method_cache(void);

static void
vm_clear_all_inline_method_cache(void)
{
    /* TODO: Clear all inline cache entries in all iseqs.
             How to iterate all iseqs in sweep phase?
             rb_objspace_each_objects() doesn't work at sweep phase.
     */
}

static void
vm_clear_all_cache()
{
    vm_clear_global_method_cache();
    vm_clear_all_inline_method_cache();
    ruby_vm_global_state_version = 1;
}

void
rb_vm_inc_const_missing_count(void)
{
    ruby_vm_const_missing_count +=1;
}

/* control stack frame */

static inline VALUE
rb_vm_set_finish_env(rb_thread_t * th)
{
    vm_push_frame(th, 0, VM_FRAME_MAGIC_FINISH,
                  Qnil, th->cfp->lfp[0], 0,
                  th->cfp->sp, 0, 1);
    th->cfp->pc = (VALUE *)&finish_insn_seq[0];
    return Qtrue;
}

static void
vm_set_top_stack(rb_thread_t * th, VALUE iseqval)
{
    rb_iseq_t *iseq;
    GetISeqPtr(iseqval, iseq);

    if (iseq->type != ISEQ_TYPE_TOP) {
        rb_raise(rb_eTypeError, "Not a toplevel InstructionSequence");
    }

    /* for return */
    rb_vm_set_finish_env(th);

    vm_push_frame(th, iseq, VM_FRAME_MAGIC_TOP,
                  th->top_self, 0, iseq->iseq_encoded,
                  th->cfp->sp, 0, iseq->local_size);

    CHECK_STACK_OVERFLOW(th->cfp, iseq->stack_max);
}

static void
vm_set_eval_stack(rb_thread_t * th, VALUE iseqval, const NODE *cref)
{
    rb_iseq_t *iseq;
    rb_block_t * const block = th->base_block;
    GetISeqPtr(iseqval, iseq);

    /* for return */
    rb_vm_set_finish_env(th);
    vm_push_frame(th, iseq, VM_FRAME_MAGIC_EVAL, block->self,
                  GC_GUARDED_PTR(block->dfp), iseq->iseq_encoded,
                  th->cfp->sp, block->lfp, iseq->local_size);

    if (cref) {
        th->cfp->dfp[-1] = (VALUE)cref;
    }

    CHECK_STACK_OVERFLOW(th->cfp, iseq->stack_max);
}

static void
vm_set_main_stack(rb_thread_t *th, VALUE iseqval)
{
    VALUE toplevel_binding = rb_const_get(rb_cObject, rb_intern("TOPLEVEL_BINDING"));
    rb_binding_t *bind;
    rb_iseq_t *iseq;
    rb_env_t *env;

    GetBindingPtr(toplevel_binding, bind);
    GetEnvPtr(bind->env, env);
    th->base_block = &env->block;
    vm_set_eval_stack(th, iseqval, 0);
    th->base_block = 0;

    /* save binding */
    GetISeqPtr(iseqval, iseq);
    if (bind && iseq->local_size > 0) {
        bind->env = rb_vm_make_env_object(th, th->cfp);
    }

    CHECK_STACK_OVERFLOW(th->cfp, iseq->stack_max);
}

rb_control_frame_t *
rb_vm_get_ruby_level_next_cfp(rb_thread_t *th, rb_control_frame_t *cfp)
{
    while (!RUBY_VM_CONTROL_FRAME_STACK_OVERFLOW_P(th, cfp)) {
        if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
            return cfp;
        }
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
    }
    return 0;
}

static rb_control_frame_t *
vm_get_ruby_level_caller_cfp(rb_thread_t *th, rb_control_frame_t *cfp)
{
    if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
        return cfp;
    }

    cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);

    while (!RUBY_VM_CONTROL_FRAME_STACK_OVERFLOW_P(th, cfp)) {
        if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
            return cfp;
        }

        if ((cfp->flag & VM_FRAME_FLAG_PASSED) == 0) {
            break;
        }
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
    }
    return 0;
}

/* at exit */

void
ruby_vm_at_exit(void (*func)(rb_vm_t *))
{
    rb_ary_push((VALUE)&GET_VM()->at_exit, (VALUE)func);
}

static void
ruby_vm_run_at_exit_hooks(rb_vm_t *vm)
{
    VALUE hook = (VALUE)&vm->at_exit;

    while (RARRAY_LEN(hook) > 0) {
        typedef void rb_vm_at_exit_func(rb_vm_t*);
        rb_vm_at_exit_func *func = (rb_vm_at_exit_func*)rb_ary_pop(hook);
        (*func)(vm);
    }
    rb_ary_free(hook);
}

/* Env */

/*
  env{
    env[0] // special (block or prev env)
    env[1] // env object
    env[2] // prev env val
  };
 */

#define ENV_IN_HEAP_P(th, env)  \
  (!((th)->stack < (env) && (env) < ((th)->stack + (th)->stack_size)))
#define ENV_VAL(env)        ((env)[1])

static void
env_mark(void * const ptr)
{
    RUBY_MARK_ENTER("env");
    if (ptr) {
        const rb_env_t * const env = ptr;

        if (env->env) {
            /* TODO: should mark more restricted range */
            RUBY_GC_INFO("env->env\n");
            rb_gc_mark_locations(env->env, env->env + env->env_size);
        }

        RUBY_GC_INFO("env->prev_envval\n");
        RUBY_MARK_UNLESS_NULL(env->prev_envval);
        RUBY_MARK_UNLESS_NULL(env->block.self);
        RUBY_MARK_UNLESS_NULL(env->block.proc);

        if (env->block.iseq) {
            if (BUILTIN_TYPE(env->block.iseq) == T_NODE) {
                RUBY_MARK_UNLESS_NULL((VALUE)env->block.iseq);
            }
            else {
                RUBY_MARK_UNLESS_NULL(env->block.iseq->self);
            }
        }
    }
    RUBY_MARK_LEAVE("env");
}

static void
env_free(void * const ptr)
{
    RUBY_FREE_ENTER("env");
    if (ptr) {
        rb_env_t *const env = ptr;
        RUBY_FREE_UNLESS_NULL(env->env);
        ruby_xfree(ptr);
    }
    RUBY_FREE_LEAVE("env");
}

static size_t
env_memsize(const void *ptr)
{
    if (ptr) {
        const rb_env_t * const env = ptr;
        size_t size = sizeof(rb_env_t);
        if (env->env) {
            size += env->env_size * sizeof(VALUE);
        }
        return size;
    }
    return 0;
}

static const rb_data_type_t env_data_type = {
    "VM/env",
    {env_mark, env_free, env_memsize,},
};

static VALUE
env_alloc(void)
{
    VALUE obj;
    rb_env_t *env;
    obj = TypedData_Make_Struct(rb_cEnv, rb_env_t, &env_data_type, env);
    env->env = 0;
    env->prev_envval = 0;
    env->block.iseq = 0;
    return obj;
}

static VALUE check_env_value(VALUE envval);

static int
check_env(rb_env_t * const env)
{
    printf("---\n");
    printf("envptr: %p\n", (void *)&env->block.dfp[0]);
    printf("orphan: %p\n", (void *)env->block.dfp[1]);
    printf("inheap: %p\n", (void *)env->block.dfp[2]);
    printf("envval: %10p ", (void *)env->block.dfp[3]);
    dp(env->block.dfp[3]);
    printf("penvv : %10p ", (void *)env->block.dfp[4]);
    dp(env->block.dfp[4]);
    printf("lfp:    %10p\n", (void *)env->block.lfp);
    printf("dfp:    %10p\n", (void *)env->block.dfp);
    if (env->block.dfp[4]) {
        printf(">>\n");
        check_env_value(env->block.dfp[4]);
        printf("<<\n");
    }
    return 1;
}

static VALUE
check_env_value(VALUE envval)
{
    rb_env_t *env;
    GetEnvPtr(envval, env);

    if (check_env(env)) {
        return envval;
    }
    rb_bug("invalid env");
    return Qnil;                /* unreachable */
}

static VALUE
vm_make_env_each(rb_thread_t * const th, rb_control_frame_t * const cfp,
                 VALUE *envptr, VALUE * const endptr)
{
    VALUE envval, penvval = 0;
    rb_env_t *env;
    VALUE *nenvptr;
    int i, local_size;

    if (ENV_IN_HEAP_P(th, envptr)) {
        return ENV_VAL(envptr);
    }

    if (envptr != endptr) {
        VALUE *penvptr = GC_GUARDED_PTR_REF(*envptr);
        rb_control_frame_t *pcfp = cfp;

        if (ENV_IN_HEAP_P(th, penvptr)) {
            penvval = ENV_VAL(penvptr);
        }
        else {
            while (pcfp->dfp != penvptr) {
                pcfp++;
                if (pcfp->dfp == 0) {
                    SDR();
                    rb_bug("invalid dfp");
                }
            }
            penvval = vm_make_env_each(th, pcfp, penvptr, endptr);
            cfp->lfp = pcfp->lfp;
            *envptr = GC_GUARDED_PTR(pcfp->dfp);
        }
    }

    /* allocate env */
    envval = env_alloc();
    GetEnvPtr(envval, env);

    if (!RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
        local_size = 2;
    }
    else {
        local_size = cfp->iseq->local_size;
    }

    env->env_size = local_size + 1 + 2;
    env->local_size = local_size;
    env->env = ALLOC_N(VALUE, env->env_size);
    env->prev_envval = penvval;

    for (i = 0; i <= local_size; i++) {
        env->env[i] = envptr[-local_size + i];
#if 0
        fprintf(stderr, "%2d ", &envptr[-local_size + i] - th->stack); dp(env->env[i]);
        if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
            /* clear value stack for GC */
            envptr[-local_size + i] = 0;
        }
#endif
    }

    *envptr = envval;           /* GC mark */
    nenvptr = &env->env[i - 1];
    nenvptr[1] = envval;        /* frame self */
    nenvptr[2] = penvval;       /* frame prev env object */

    /* reset lfp/dfp in cfp */
    cfp->dfp = nenvptr;
    if (envptr == endptr) {
        cfp->lfp = nenvptr;
    }

    /* as Binding */
    env->block.self = cfp->self;
    env->block.lfp = cfp->lfp;
    env->block.dfp = cfp->dfp;
    env->block.iseq = cfp->iseq;

    if (!RUBY_VM_NORMAL_ISEQ_P(cfp->iseq)) {
        /* TODO */
        env->block.iseq = 0;
    }
    return envval;
}

static int
collect_local_variables_in_iseq(rb_iseq_t *iseq, const VALUE ary)
{
    int i;
    if (!iseq) return 0;
    for (i = 0; i < iseq->local_table_size; i++) {
        ID lid = iseq->local_table[i];
        if (rb_is_local_id(lid)) {
            rb_ary_push(ary, ID2SYM(lid));
        }
    }
    return 1;
}

static int
collect_local_variables_in_env(rb_env_t * env, const VALUE ary)
{

    while (collect_local_variables_in_iseq(env->block.iseq, ary),
           env->prev_envval) {
        GetEnvPtr(env->prev_envval, env);
    }
    return 0;
}

static int
vm_collect_local_variables_in_heap(rb_thread_t *th, VALUE *dfp, VALUE ary)
{
    if (ENV_IN_HEAP_P(th, dfp)) {
        rb_env_t *env;
        GetEnvPtr(ENV_VAL(dfp), env);
        collect_local_variables_in_env(env, ary);
        return 1;
    }
    else {
        return 0;
    }
}

VALUE
rb_vm_make_env_object(rb_thread_t * th, rb_control_frame_t *cfp)
{
    VALUE envval;

    if (VM_FRAME_TYPE(cfp) == VM_FRAME_MAGIC_FINISH) {
        /* for method_missing */
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
    }

    envval = vm_make_env_each(th, cfp, cfp->dfp, cfp->lfp);
    rb_vm_rewrite_dfp_in_errinfo(th);

    if (PROCDEBUG) {
        check_env_value(envval);
    }

    return envval;
}

void
rb_vm_rewrite_dfp_in_errinfo(rb_thread_t *th)
{
    rb_control_frame_t *cfp = th->cfp;
    while (!RUBY_VM_CONTROL_FRAME_STACK_OVERFLOW_P(th, cfp)) {
        /* rewrite dfp in errinfo to point to heap */
        if (RUBY_VM_NORMAL_ISEQ_P(cfp->iseq) &&
            (cfp->iseq->type == ISEQ_TYPE_RESCUE ||
             cfp->iseq->type == ISEQ_TYPE_ENSURE)) {
            VALUE errinfo = cfp->dfp[-2]; /* #$! */
            if (RB_TYPE_P(errinfo, T_NODE)) {
                VALUE *escape_dfp = GET_THROWOBJ_CATCH_POINT(errinfo);
                if (! ENV_IN_HEAP_P(th, escape_dfp)) {
                    VALUE dfpval = *escape_dfp;
                    if (CLASS_OF(dfpval) == rb_cEnv) {
                        rb_env_t *dfpenv;
                        GetEnvPtr(dfpval, dfpenv);
                        SET_THROWOBJ_CATCH_POINT(errinfo, (VALUE)(dfpenv->env + dfpenv->local_size));
                    }
                }
            }
        }
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
    }
}

void
rb_vm_stack_to_heap(rb_thread_t *th)
{
    rb_control_frame_t *cfp = th->cfp;
    while ((cfp = rb_vm_get_ruby_level_next_cfp(th, cfp)) != 0) {
        rb_vm_make_env_object(th, cfp);
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
    }
}

/* Proc */

static VALUE
vm_make_proc_from_block(rb_thread_t *th, rb_block_t *block)
{
    if (!block->proc) {
        block->proc = rb_vm_make_proc(th, block, rb_cProc);
    }
    return block->proc;
}

VALUE
rb_vm_make_proc(rb_thread_t *th, const rb_block_t *block, VALUE klass)
{
    VALUE procval, envval, blockprocval = 0;
    rb_proc_t *proc;
    rb_control_frame_t *cfp = RUBY_VM_GET_CFP_FROM_BLOCK_PTR(block);

    if (block->proc) {
        rb_bug("rb_vm_make_proc: Proc value is already created.");
    }

    if (GC_GUARDED_PTR_REF(cfp->lfp[0])) {
        rb_proc_t *p;

        blockprocval = vm_make_proc_from_block(
            th, (rb_block_t *)GC_GUARDED_PTR_REF(*cfp->lfp));

        GetProcPtr(blockprocval, p);
        *cfp->lfp = GC_GUARDED_PTR(&p->block);
    }

    envval = rb_vm_make_env_object(th, cfp);

    if (PROCDEBUG) {
        check_env_value(envval);
    }
    procval = rb_proc_alloc(klass);
    GetProcPtr(procval, proc);
    proc->blockprocval = blockprocval;
    proc->block.self = block->self;
    proc->block.lfp = block->lfp;
    proc->block.dfp = block->dfp;
    proc->block.iseq = block->iseq;
    proc->block.proc = procval;
    proc->envval = envval;
    proc->safe_level = th->safe_level;

    if (VMDEBUG) {
        if (th->stack < block->dfp && block->dfp < th->stack + th->stack_size) {
            rb_bug("invalid ptr: block->dfp");
        }
        if (th->stack < block->lfp && block->lfp < th->stack + th->stack_size) {
            rb_bug("invalid ptr: block->lfp");
        }
    }

    return procval;
}

/* C -> Ruby: block */

static inline VALUE
invoke_block_from_c(rb_thread_t *th, const rb_block_t *block,
                    VALUE self, int argc, const VALUE *argv,
                    const rb_block_t *blockptr, const NODE *cref)
{
    if (SPECIAL_CONST_P(block->iseq))
        return Qnil;
    else if (BUILTIN_TYPE(block->iseq) != T_NODE) {
        const rb_iseq_t *iseq = block->iseq;
        const rb_control_frame_t *cfp;
        rb_control_frame_t *ncfp;
        int i, opt_pc, arg_size = iseq->arg_size;
        int type = block_proc_is_lambda(block->proc) ?
          VM_FRAME_MAGIC_LAMBDA : VM_FRAME_MAGIC_BLOCK;

        rb_vm_set_finish_env(th);

        cfp = th->cfp;
        CHECK_STACK_OVERFLOW(cfp, argc + iseq->stack_max);

        for (i=0; i<argc; i++) {
            cfp->sp[i] = argv[i];
        }

        opt_pc = vm_yield_setup_args(th, iseq, argc, cfp->sp, blockptr,
                                     type == VM_FRAME_MAGIC_LAMBDA);

        ncfp = vm_push_frame(th, iseq, type,
                             self, GC_GUARDED_PTR(block->dfp),
                             iseq->iseq_encoded + opt_pc, cfp->sp + arg_size, block->lfp,
                             iseq->local_size - arg_size);
        ncfp->me = th->passed_me;
        th->passed_me = 0;
        th->passed_block = blockptr;

        if (cref) {
            th->cfp->dfp[-1] = (VALUE)cref;
        }

        return vm_exec(th);
    }
    else {
        return vm_yield_with_cfunc(th, block, self, argc, argv, blockptr);
    }
}

static inline const rb_block_t *
check_block(rb_thread_t *th)
{
    const rb_block_t *blockptr = GC_GUARDED_PTR_REF(th->cfp->lfp[0]);

    if (blockptr == 0) {
        rb_vm_localjump_error("no block given", Qnil, 0);
    }

    return blockptr;
}

static inline VALUE
vm_yield_with_cref(rb_thread_t *th, int argc, const VALUE *argv, const NODE *cref)
{
    const rb_block_t *blockptr = check_block(th);
    return invoke_block_from_c(th, blockptr, blockptr->self, argc, argv, 0, cref);
}

static inline VALUE
vm_yield(rb_thread_t *th, int argc, const VALUE *argv)
{
    const rb_block_t *blockptr = check_block(th);
    return invoke_block_from_c(th, blockptr, blockptr->self, argc, argv, 0, 0);
}

VALUE
rb_vm_invoke_proc(rb_thread_t *th, rb_proc_t *proc, VALUE self,
                  int argc, const VALUE *argv, const rb_block_t * blockptr)
{
    VALUE val = Qundef;
    int state;
    volatile int stored_safe = th->safe_level;

    TH_PUSH_TAG(th);
    if ((state = EXEC_TAG()) == 0) {
        if (!proc->is_from_method) {
            th->safe_level = proc->safe_level;
        }
        val = invoke_block_from_c(th, &proc->block, self, argc, argv, blockptr, 0);
    }
    TH_POP_TAG();

    if (!proc->is_from_method) {
        th->safe_level = stored_safe;
    }

    if (state) {
        JUMP_TAG(state);
    }
    return val;
}

/* special variable */

static rb_control_frame_t *
vm_normal_frame(rb_thread_t *th, rb_control_frame_t *cfp)
{
    while (cfp->pc == 0) {
        cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
        if (RUBY_VM_CONTROL_FRAME_STACK_OVERFLOW_P(th, cfp)) {
            return 0;
        }
    }
    return cfp;
}

static VALUE
vm_cfp_svar_get(rb_thread_t *th, rb_control_frame_t *cfp, VALUE key)
{
    cfp = vm_normal_frame(th, cfp);
    return lfp_svar_get(th, cfp ? cfp->lfp : 0, key);
}

static void
vm_cfp_svar_set(rb_thread_t *th, rb_control_frame_t *cfp, VALUE key, const VALUE val)
{
    cfp = vm_normal_frame(th, cfp);
    lfp_svar_set(th, cfp ? cfp->lfp : 0, key, val);
}

static VALUE
vm_svar_get(VALUE key)
{
    rb_thread_t *th = GET_THREAD();
    return vm_cfp_svar_get(th, th->cfp, key);
}

static void
vm_svar_set(VALUE key, VALUE val)
{
    rb_thread_t *th = GET_THREAD();
    vm_cfp_svar_set(th, th->cfp, key, val);
}

VALUE
rb_backref_get(void)
{
    return vm_svar_get(1);
}

void
rb_backref_set(VALUE val)
{
    vm_svar_set(1, val);
}

VALUE
rb_lastline_get(void)
{
    return vm_svar_get(0);
}

void
rb_lastline_set(VALUE val)
{
    vm_svar_set(0, val);
}

/* backtrace */

int
rb_vm_get_sourceline(const rb_control_frame_t *cfp)
{
    int line_no = 0;
    const rb_iseq_t *iseq = cfp->iseq;

    if (RUBY_VM_NORMAL_ISEQ_P(iseq) && iseq->insn_info_size > 0) {
        rb_num_t i;
        size_t pos = cfp->pc - cfp->iseq->iseq_encoded;

        if (iseq->insn_info_table[0].position == pos) goto found;
        for (i = 1; i < iseq->insn_info_size; i++) {
            if (iseq->insn_info_table[i].position == pos) {
                line_no = iseq->insn_info_table[i - 1].line_no;
                goto found;
            }
        }
        line_no = iseq->insn_info_table[i - 1].line_no;
    }
  found:
    return line_no;
}

static int
vm_backtrace_each(rb_thread_t *th, int lev, void (*init)(void *), rb_backtrace_iter_func *iter, void *arg)
{
    const rb_control_frame_t *limit_cfp = th->cfp;
    const rb_control_frame_t *cfp = (void *)(th->stack + th->stack_size);
    VALUE file = Qnil;
    int line_no = 0;

    cfp -= 2;
    while (lev-- >= 0) {
        if (++limit_cfp > cfp) {
            return FALSE;
        }
    }
    if (init) (*init)(arg);
    limit_cfp = RUBY_VM_NEXT_CONTROL_FRAME(limit_cfp);
    if (th->vm->progname) file = th->vm->progname;
    while (cfp > limit_cfp) {
        if (cfp->iseq != 0) {
            if (cfp->pc != 0) {
                rb_iseq_t *iseq = cfp->iseq;

                line_no = rb_vm_get_sourceline(cfp);
                file = iseq->filename;
                if ((*iter)(arg, file, line_no, iseq->name)) break;
            }
        }
        else if (RUBYVM_CFUNC_FRAME_P(cfp)) {
            ID id;
            extern VALUE ruby_engine_name;

            if (NIL_P(file)) file = ruby_engine_name;
            if (cfp->me->def)
                id = cfp->me->def->original_id;
            else
                id = cfp->me->called_id;
            if (id != ID_ALLOCATOR && (*iter)(arg, file, line_no, rb_id2str(id)))
                break;
        }
        cfp = RUBY_VM_NEXT_CONTROL_FRAME(cfp);
    }
    return TRUE;
}

static void
vm_backtrace_alloc(void *arg)
{
    VALUE *aryp = arg;
    *aryp = rb_ary_new();
}

static int
vm_backtrace_push(void *arg, VALUE file, int line_no, VALUE name)
{
    VALUE *aryp = arg;
    VALUE bt;

    if (line_no) {
        bt = rb_enc_sprintf(rb_enc_compatible(file, name), "%s:%d:in `%s'",
                            RSTRING_PTR(file), line_no, RSTRING_PTR(name));
    }
    else {
        bt = rb_enc_sprintf(rb_enc_compatible(file, name), "%s:in `%s'",
                            RSTRING_PTR(file), RSTRING_PTR(name));
    }
    rb_ary_push(*aryp, bt);
    return 0;
}

static inline VALUE
vm_backtrace(rb_thread_t *th, int lev)
{
    VALUE ary = 0;

    if (lev < 0) {
        ary = rb_ary_new();
    }
    vm_backtrace_each(th, lev, vm_backtrace_alloc, vm_backtrace_push, &ary);
    if (!ary) return Qnil;
    return rb_ary_reverse(ary);
}

const char *
rb_sourcefile(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);

    if (cfp) {
        return RSTRING_PTR(cfp->iseq->filename);
    }
    else {
        return 0;
    }
}

int
rb_sourceline(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);

    if (cfp) {
        return rb_vm_get_sourceline(cfp);
    }
    else {
        return 0;
    }
}

NODE *
rb_vm_cref(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);

    if (cfp == 0) {
        rb_raise(rb_eRuntimeError, "Can't call on top of Fiber or Thread");
    }
    return vm_get_cref(cfp->iseq, cfp->lfp, cfp->dfp);
}

#if 0
void
debug_cref(NODE *cref)
{
    while (cref) {
        dp(cref->nd_clss);
        printf("%ld\n", cref->nd_visi);
        cref = cref->nd_next;
    }
}
#endif

VALUE
rb_vm_cbase(void)
{
    rb_thread_t *th = GET_THREAD();
    rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);

    if (cfp == 0) {
        rb_raise(rb_eRuntimeError, "Can't call on top of Fiber or Thread");
    }
    return vm_get_cbase(cfp->iseq, cfp->lfp, cfp->dfp);
}

/* jump */

static VALUE
make_localjump_error(const char *mesg, VALUE value, int reason)
{
    extern VALUE rb_eLocalJumpError;
    VALUE exc = rb_exc_new2(rb_eLocalJumpError, mesg);
    ID id;

    switch (reason) {
      case TAG_BREAK:
        CONST_ID(id, "break");
        break;
      case TAG_REDO:
        CONST_ID(id, "redo");
        break;
      case TAG_RETRY:
        CONST_ID(id, "retry");
        break;
      case TAG_NEXT:
        CONST_ID(id, "next");
        break;
      case TAG_RETURN:
        CONST_ID(id, "return");
        break;
      default:
        CONST_ID(id, "noreason");
        break;
    }
    rb_iv_set(exc, "@exit_value", value);
    rb_iv_set(exc, "@reason", ID2SYM(id));
    return exc;
}

void
rb_vm_localjump_error(const char *mesg, VALUE value, int reason)
{
    VALUE exc = make_localjump_error(mesg, value, reason);
    rb_exc_raise(exc);
}

VALUE
rb_vm_make_jump_tag_but_local_jump(int state, VALUE val)
{
    VALUE result = Qnil;

    if (val == Qundef) {
        val = GET_THREAD()->tag->retval;
    }
    switch (state) {
      case 0:
        break;
      case TAG_RETURN:
        result = make_localjump_error("unexpected return", val, state);
        break;
      case TAG_BREAK:
        result = make_localjump_error("unexpected break", val, state);
        break;
      case TAG_NEXT:
        result = make_localjump_error("unexpected next", val, state);
        break;
      case TAG_REDO:
        result = make_localjump_error("unexpected redo", Qnil, state);
        break;
      case TAG_RETRY:
        result = make_localjump_error("retry outside of rescue clause", Qnil, state);
        break;
      default:
        break;
    }
    return result;
}

void
rb_vm_jump_tag_but_local_jump(int state, VALUE val)
{
    if (val != Qnil) {
        VALUE exc = rb_vm_make_jump_tag_but_local_jump(state, val);
        if (!NIL_P(exc)) rb_exc_raise(exc);
    }
    JUMP_TAG(state);
}

NORETURN(static void vm_iter_break(rb_thread_t *th));

static void
vm_iter_break(rb_thread_t *th)
{
    rb_control_frame_t *cfp = th->cfp;
    VALUE *dfp = GC_GUARDED_PTR_REF(*cfp->dfp);

    th->state = TAG_BREAK;
    th->errinfo = (VALUE)NEW_THROW_OBJECT(Qnil, (VALUE)dfp, TAG_BREAK);
    TH_JUMP_TAG(th, TAG_BREAK);
}

void
rb_iter_break(void)
{
    vm_iter_break(GET_THREAD());
}

/* optimization: redefine management */

static st_table *vm_opt_method_table = 0;

static void
rb_vm_check_redefinition_opt_method(const rb_method_entry_t *me)
{
    st_data_t bop;
    if (!me->def || me->def->type == VM_METHOD_TYPE_CFUNC) {
        if (st_lookup(vm_opt_method_table, (st_data_t)me, &bop)) {
            ruby_vm_redefined_flag[bop] = 1;
        }
    }
}

static void
add_opt_method(VALUE klass, ID mid, VALUE bop)
{
    rb_method_entry_t *me;
    if (st_lookup(RCLASS_M_TBL(klass), mid, (void *)&me) && me->def &&
        me->def->type == VM_METHOD_TYPE_CFUNC) {
        st_insert(vm_opt_method_table, (st_data_t)me, (st_data_t)bop);
    }
    else {
        rb_bug("undefined optimized method: %s", rb_id2name(mid));
    }
}

static void
vm_init_redefined_flag(void)
{
    ID mid;
    VALUE bop;

    vm_opt_method_table = st_init_numtable();

#define OP(mid_, bop_) (mid = id##mid_, bop = BOP_##bop_, ruby_vm_redefined_flag[bop] = 0)
#define C(k) add_opt_method(rb_c##k, mid, bop)
    OP(PLUS, PLUS), (C(Fixnum), C(Float), C(String), C(Array));
    OP(MINUS, MINUS), (C(Fixnum));
    OP(MULT, MULT), (C(Fixnum), C(Float));
    OP(DIV, DIV), (C(Fixnum), C(Float));
    OP(MOD, MOD), (C(Fixnum), C(Float));
    OP(Eq, EQ), (C(Fixnum), C(Float), C(String));
    OP(Eqq, EQQ), (C(Fixnum), C(Bignum), C(Float), C(Symbol), C(String));
    OP(LT, LT), (C(Fixnum));
    OP(LE, LE), (C(Fixnum));
    OP(LTLT, LTLT), (C(String), C(Array));
    OP(AREF, AREF), (C(Array), C(Hash));
    OP(ASET, ASET), (C(Array), C(Hash));
    OP(Length, LENGTH), (C(Array), C(String), C(Hash));
    OP(Size, SIZE), (C(Array), C(String), C(Hash));
    OP(Succ, SUCC), (C(Fixnum), C(String), C(Time));
    OP(GT, GT), (C(Fixnum));
    OP(GE, GE), (C(Fixnum));
#undef C
#undef OP
}

/* for vm development */

#if VMDEBUG
static const char *
vm_frametype_name(const rb_control_frame_t *cfp)
{
    switch (VM_FRAME_TYPE(cfp)) {
      case VM_FRAME_MAGIC_METHOD: return "method";
      case VM_FRAME_MAGIC_BLOCK:  return "block";
      case VM_FRAME_MAGIC_CLASS:  return "class";
      case VM_FRAME_MAGIC_TOP:    return "top";
      case VM_FRAME_MAGIC_FINISH: return "finish";
      case VM_FRAME_MAGIC_CFUNC:  return "cfunc";
      case VM_FRAME_MAGIC_PROC:   return "proc";
      case VM_FRAME_MAGIC_IFUNC:  return "ifunc";
      case VM_FRAME_MAGIC_EVAL:   return "eval";
      case VM_FRAME_MAGIC_LAMBDA: return "lambda";
      default:
        rb_bug("unknown frame");
    }
}
#endif

/* evaluator body */

/*                  finish
  VMe (h1)          finish
    VM              finish F1 F2
      cfunc         finish F1 F2 C1
        rb_funcall  finish F1 F2 C1
          VMe       finish F1 F2 C1
            VM      finish F1 F2 C1 F3

  F1 - F3 : pushed by VM
  C1      : pushed by send insn (CFUNC)

  struct CONTROL_FRAME {
    VALUE *pc;                  // cfp[0], program counter
    VALUE *sp;                  // cfp[1], stack pointer
    VALUE *bp;                  // cfp[2], base pointer
    rb_iseq_t *iseq;            // cfp[3], iseq
    VALUE flag;                 // cfp[4], magic
    VALUE self;                 // cfp[5], self
    VALUE *lfp;                 // cfp[6], local frame pointer
    VALUE *dfp;                 // cfp[7], dynamic frame pointer
    rb_iseq_t * block_iseq;     // cfp[8], block iseq
    VALUE proc;                 // cfp[9], always 0
  };

  struct BLOCK {
    VALUE self;
    VALUE *lfp;
    VALUE *dfp;
    rb_iseq_t *block_iseq;
    VALUE proc;
  };

  struct METHOD_CONTROL_FRAME {
    rb_control_frame_t frame;
  };

  struct METHOD_FRAME {
    VALUE arg0;
    ...
    VALUE argM;
    VALUE param0;
    ...
    VALUE paramN;
    VALUE cref;
    VALUE special;                         // lfp [1]
    struct block_object *block_ptr | 0x01; // lfp [0]
  };

  struct BLOCK_CONTROL_FRAME {
    rb_control_frame_t frame;
  };

  struct BLOCK_FRAME {
    VALUE arg0;
    ...
    VALUE argM;
    VALUE param0;
    ...
    VALUE paramN;
    VALUE cref;
    VALUE *(prev_ptr | 0x01); // DFP[0]
  };

  struct CLASS_CONTROL_FRAME {
    rb_control_frame_t frame;
  };

  struct CLASS_FRAME {
    VALUE param0;
    ...
    VALUE paramN;
    VALUE cref;
    VALUE prev_dfp; // for frame jump
  };

  struct C_METHOD_CONTROL_FRAME {
    VALUE *pc;                       // 0
    VALUE *sp;                       // stack pointer
    VALUE *bp;                       // base pointer (used in exception)
    rb_iseq_t *iseq;               // cmi
    VALUE magic;                     // C_METHOD_FRAME
    VALUE self;                      // ?
    VALUE *lfp;                      // lfp
    VALUE *dfp;                      // == lfp
    rb_iseq_t * block_iseq;        //
    VALUE proc;                      // always 0
  };

  struct C_BLOCK_CONTROL_FRAME {
    VALUE *pc;                       // point only "finish" insn
    VALUE *sp;                       // sp
    rb_iseq_t *iseq;               // ?
    VALUE magic;                     // C_METHOD_FRAME
    VALUE self;                      // needed?
    VALUE *lfp;                      // lfp
    VALUE *dfp;                      // lfp
    rb_iseq_t * block_iseq; // 0
  };
 */


static VALUE
vm_exec(rb_thread_t *th)
{
    int state;
    VALUE result, err;
    VALUE initial = 0;
    VALUE *escape_dfp = NULL;

    TH_PUSH_TAG(th);
    _tag.retval = Qnil;
    if ((state = EXEC_TAG()) == 0) {
      vm_loop_start:
        result = vm_exec_core(th, initial);
        if ((state = th->state) != 0) {
            err = result;
            th->state = 0;
            goto exception_handler;
        }
    }
    else {
        int i;
        struct iseq_catch_table_entry *entry;
        unsigned long epc, cont_pc, cont_sp;
        VALUE catch_iseqval;
        rb_control_frame_t *cfp;
        VALUE type;

        err = th->errinfo;

      exception_handler:
        cont_pc = cont_sp = catch_iseqval = 0;

        while (th->cfp->pc == 0 || th->cfp->iseq == 0) {
            if (UNLIKELY(VM_FRAME_TYPE(th->cfp) == VM_FRAME_MAGIC_CFUNC)) {
                const rb_method_entry_t *me = th->cfp->me;
                EXEC_EVENT_HOOK(th, RUBY_EVENT_C_RETURN, th->cfp->self, me->called_id, me->klass);
            }
            th->cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(th->cfp);
        }

        cfp = th->cfp;
        epc = cfp->pc - cfp->iseq->iseq_encoded;

        if (state == TAG_BREAK || state == TAG_RETURN) {
            escape_dfp = GET_THROWOBJ_CATCH_POINT(err);

            if (cfp->dfp == escape_dfp) {
                if (state == TAG_RETURN) {
                    if ((cfp + 1)->pc != &finish_insn_seq[0]) {
                        SET_THROWOBJ_CATCH_POINT(err, (VALUE)(cfp + 1)->dfp);
                        SET_THROWOBJ_STATE(err, state = TAG_BREAK);
                    }
                    else {
                        for (i = 0; i < cfp->iseq->catch_table_size; i++) {
                            entry = &cfp->iseq->catch_table[i];
                            if (entry->start < epc && entry->end >= epc) {
                                if (entry->type == CATCH_TYPE_ENSURE) {
                                    catch_iseqval = entry->iseq;
                                    cont_pc = entry->cont;
                                    cont_sp = entry->sp;
                                    break;
                                }
                            }
                        }
                        if (!catch_iseqval) {
                            result = GET_THROWOBJ_VAL(err);
                            th->errinfo = Qnil;
                            th->cfp += 2;
                            goto finish_vme;
                        }
                    }
                    /* through */
                }
                else {
                    /* TAG_BREAK */
#if OPT_STACK_CACHING
                    initial = (GET_THROWOBJ_VAL(err));
#else
                    *th->cfp->sp++ = (GET_THROWOBJ_VAL(err));
#endif
                    th->errinfo = Qnil;
                    goto vm_loop_start;
                }
            }
        }

        if (state == TAG_RAISE) {
            for (i = 0; i < cfp->iseq->catch_table_size; i++) {
                entry = &cfp->iseq->catch_table[i];
                if (entry->start < epc && entry->end >= epc) {

                    if (entry->type == CATCH_TYPE_RESCUE ||
                        entry->type == CATCH_TYPE_ENSURE) {
                        catch_iseqval = entry->iseq;
                        cont_pc = entry->cont;
                        cont_sp = entry->sp;
                        break;
                    }
                }
            }
        }
        else if (state == TAG_RETRY) {
            for (i = 0; i < cfp->iseq->catch_table_size; i++) {
                entry = &cfp->iseq->catch_table[i];
                if (entry->start < epc && entry->end >= epc) {

                    if (entry->type == CATCH_TYPE_ENSURE) {
                        catch_iseqval = entry->iseq;
                        cont_pc = entry->cont;
                        cont_sp = entry->sp;
                        break;
                    }
                    else if (entry->type == CATCH_TYPE_RETRY) {
                        VALUE *escape_dfp;
                        escape_dfp = GET_THROWOBJ_CATCH_POINT(err);
                        if (cfp->dfp == escape_dfp) {
                            cfp->pc = cfp->iseq->iseq_encoded + entry->cont;
                            th->errinfo = Qnil;
                            goto vm_loop_start;
                        }
                    }
                }
            }
        }
        else if (state == TAG_BREAK && ((VALUE)escape_dfp & ~0x03) == 0) {
            type = CATCH_TYPE_BREAK;

          search_restart_point:
            for (i = 0; i < cfp->iseq->catch_table_size; i++) {
                entry = &cfp->iseq->catch_table[i];

                if (entry->start < epc && entry->end >= epc) {
                    if (entry->type == CATCH_TYPE_ENSURE) {
                        catch_iseqval = entry->iseq;
                        cont_pc = entry->cont;
                        cont_sp = entry->sp;
                        break;
                    }
                    else if (entry->type == type) {
                        cfp->pc = cfp->iseq->iseq_encoded + entry->cont;
                        cfp->sp = cfp->bp + entry->sp;

                        if (state != TAG_REDO) {
#if OPT_STACK_CACHING
                            initial = (GET_THROWOBJ_VAL(err));
#else
                            *th->cfp->sp++ = (GET_THROWOBJ_VAL(err));
#endif
                        }
                        th->errinfo = Qnil;
                        goto vm_loop_start;
                    }
                }
            }
        }
        else if (state == TAG_REDO) {
            type = CATCH_TYPE_REDO;
            goto search_restart_point;
        }
        else if (state == TAG_NEXT) {
            type = CATCH_TYPE_NEXT;
            goto search_restart_point;
        }
        else {
            for (i = 0; i < cfp->iseq->catch_table_size; i++) {
                entry = &cfp->iseq->catch_table[i];
                if (entry->start < epc && entry->end >= epc) {

                    if (entry->type == CATCH_TYPE_ENSURE) {
                        catch_iseqval = entry->iseq;
                        cont_pc = entry->cont;
                        cont_sp = entry->sp;
                        break;
                    }
                }
            }
        }

        if (catch_iseqval != 0) {
            /* found catch table */
            rb_iseq_t *catch_iseq;

            /* enter catch scope */
            GetISeqPtr(catch_iseqval, catch_iseq);
            cfp->sp = cfp->bp + cont_sp;
            cfp->pc = cfp->iseq->iseq_encoded + cont_pc;

            /* push block frame */
            cfp->sp[0] = err;
            vm_push_frame(th, catch_iseq, VM_FRAME_MAGIC_BLOCK,
                          cfp->self, (VALUE)cfp->dfp, catch_iseq->iseq_encoded,
                          cfp->sp + 1 /* push value */, cfp->lfp, catch_iseq->local_size - 1);

            state = 0;
            th->state = 0;
            th->errinfo = Qnil;
            goto vm_loop_start;
        }
        else {
            /* skip frame */

            switch (VM_FRAME_TYPE(th->cfp)) {
              case VM_FRAME_MAGIC_METHOD:
                EXEC_EVENT_HOOK(th, RUBY_EVENT_RETURN, th->cfp->self, 0, 0);
                break;
              case VM_FRAME_MAGIC_CLASS:
                EXEC_EVENT_HOOK(th, RUBY_EVENT_END, th->cfp->self, 0, 0);
                break;
            }

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

            if (VM_FRAME_TYPE(th->cfp) != VM_FRAME_MAGIC_FINISH) {
                goto exception_handler;
            }
            else {
                vm_pop_frame(th);
                th->errinfo = err;
                TH_POP_TAG2();
                JUMP_TAG(state);
            }
        }
    }
  finish_vme:
    TH_POP_TAG();
    return result;
}

/* misc */

VALUE
rb_iseq_eval(VALUE iseqval)
{
    rb_thread_t *th = GET_THREAD();
    VALUE val;
    volatile VALUE tmp;

    vm_set_top_stack(th, iseqval);

    val = vm_exec(th);
    tmp = iseqval; /* prohibit tail call optimization */
    return val;
}

VALUE
rb_iseq_eval_main(VALUE iseqval)
{
    rb_thread_t *th = GET_THREAD();
    VALUE val;
    volatile VALUE tmp;

    vm_set_main_stack(th, iseqval);

    val = vm_exec(th);
    tmp = iseqval; /* prohibit tail call optimization */
    return val;
}

int
rb_thread_method_id_and_class(rb_thread_t *th,
                              ID *idp, VALUE *klassp)
{
    rb_control_frame_t *cfp = th->cfp;
    rb_iseq_t *iseq = cfp->iseq;
    if (!iseq && cfp->me) {
        if (idp) *idp = cfp->me->def->original_id;
        if (klassp) *klassp = cfp->me->klass;
        return 1;
    }
    while (iseq) {
        if (RUBY_VM_IFUNC_P(iseq)) {
            if (idp) CONST_ID(*idp, "<ifunc>");
            if (klassp) *klassp = 0;
            return 1;
        }
        if (iseq->defined_method_id) {
            if (idp) *idp = iseq->defined_method_id;
            if (klassp) *klassp = iseq->klass;
            return 1;
        }
        if (iseq->local_iseq == iseq) {
            break;
        }
        iseq = iseq->parent_iseq;
    }
    return 0;
}

int
rb_frame_method_id_and_class(ID *idp, VALUE *klassp)
{
    return rb_thread_method_id_and_class(GET_THREAD(), idp, klassp);
}

VALUE
rb_thread_current_status(const rb_thread_t *th)
{
    const rb_control_frame_t *cfp = th->cfp;
    VALUE str = Qnil;

    if (cfp->iseq != 0) {
        if (cfp->pc != 0) {
            rb_iseq_t *iseq = cfp->iseq;
            int line_no = rb_vm_get_sourceline(cfp);
            char *file = RSTRING_PTR(iseq->filename);
            str = rb_sprintf("%s:%d:in `%s'",
                             file, line_no, RSTRING_PTR(iseq->name));
        }
    }
    else if (cfp->me->def->original_id) {
        str = rb_sprintf("`%s#%s' (cfunc)",
                         rb_class2name(cfp->me->klass),
                         rb_id2name(cfp->me->def->original_id));
    }

    return str;
}

VALUE
rb_vm_call_cfunc(VALUE recv, VALUE (*func)(VALUE), VALUE arg,
                 const rb_block_t *blockptr, VALUE filename)
{
    rb_thread_t *th = GET_THREAD();
    const rb_control_frame_t *reg_cfp = th->cfp;
    volatile VALUE iseqval = rb_iseq_new(0, filename, filename, Qnil, 0, ISEQ_TYPE_TOP);
    VALUE val;

    vm_push_frame(th, DATA_PTR(iseqval), VM_FRAME_MAGIC_TOP,
                  recv, (VALUE)blockptr, 0, reg_cfp->sp, 0, 1);

    val = (*func)(arg);

    vm_pop_frame(th);
    return val;
}

/* vm */

static int
vm_mark_each_thread_func(st_data_t key, st_data_t value, st_data_t dummy)
{
    VALUE thval = (VALUE)key;
    rb_gc_mark(thval);
    return ST_CONTINUE;
}

static void
mark_event_hooks(rb_event_hook_t *hook)
{
    while (hook) {
        rb_gc_mark(hook->data);
        hook = hook->next;
    }
}

void
rb_vm_mark(void *ptr)
{
    int i;

    RUBY_MARK_ENTER("vm");
    RUBY_GC_INFO("-------------------------------------------------\n");
    if (ptr) {
        rb_vm_t *vm = ptr;
        if (vm->living_threads) {
            st_foreach(vm->living_threads, vm_mark_each_thread_func, 0);
        }
        RUBY_MARK_UNLESS_NULL(vm->thgroup_default);
        RUBY_MARK_UNLESS_NULL(vm->mark_object_ary);
        RUBY_MARK_UNLESS_NULL(vm->load_path);
        RUBY_MARK_UNLESS_NULL(vm->loaded_features);
        RUBY_MARK_UNLESS_NULL(vm->top_self);
        RUBY_MARK_UNLESS_NULL(vm->coverages);
        rb_gc_mark_locations(vm->special_exceptions, vm->special_exceptions + ruby_special_error_count);

        if (vm->loading_table) {
            rb_mark_tbl(vm->loading_table);
        }

        mark_event_hooks(vm->event_hooks);

        for (i = 0; i < RUBY_NSIG; i++) {
            if (vm->trap_list[i].cmd)
                rb_gc_mark(vm->trap_list[i].cmd);
        }
    }

    RUBY_MARK_LEAVE("vm");
}

#define vm_free 0

int
ruby_vm_destruct(rb_vm_t *vm)
{
    RUBY_FREE_ENTER("vm");
    if (vm) {
        rb_thread_t *th = vm->main_thread;
#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
        struct rb_objspace *objspace = vm->objspace;
#endif
        rb_gc_force_recycle(vm->self);
        vm->main_thread = 0;
        if (th) {
            rb_fiber_reset_root_local_storage(th->self);
            thread_free(th);
        }
        if (vm->living_threads) {
            st_free_table(vm->living_threads);
            vm->living_threads = 0;
        }
#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
        if (objspace) {
            rb_objspace_free(objspace);
        }
#endif
        ruby_vm_run_at_exit_hooks(vm);
        rb_vm_gvl_destroy(vm);
        ruby_xfree(vm);
        ruby_current_vm = 0;
    }
    RUBY_FREE_LEAVE("vm");
    return 0;
}

static size_t
vm_memsize(const void *ptr)
{
    if (ptr) {
        const rb_vm_t *vmobj = ptr;
        return sizeof(rb_vm_t) + st_memsize(vmobj->living_threads);
    }
    else {
        return 0;
    }
}

static const rb_data_type_t vm_data_type = {
    "VM",
    {rb_vm_mark, vm_free, vm_memsize,},
};

static void
vm_init2(rb_vm_t *vm)
{
    MEMZERO(vm, rb_vm_t, 1);
    vm->src_encoding_index = -1;
    vm->at_exit.basic.flags = (T_ARRAY | RARRAY_EMBED_FLAG) & ~RARRAY_EMBED_LEN_MASK; /* len set 0 */
    vm->at_exit.basic.klass = 0;
}

/* Thread */

#define USE_THREAD_DATA_RECYCLE 1

#if USE_THREAD_DATA_RECYCLE
#define RECYCLE_MAX 64
static VALUE *thread_recycle_stack_slot[RECYCLE_MAX];
static int thread_recycle_stack_count = 0;

static VALUE *
thread_recycle_stack(size_t size)
{
    if (thread_recycle_stack_count) {
        return thread_recycle_stack_slot[--thread_recycle_stack_count];
    }
    else {
        return ALLOC_N(VALUE, size);
    }
}

#else
#define thread_recycle_stack(size) ALLOC_N(VALUE, (size))
#endif

void
rb_thread_recycle_stack_release(VALUE *stack)
{
#if USE_THREAD_DATA_RECYCLE
    if (thread_recycle_stack_count < RECYCLE_MAX) {
        thread_recycle_stack_slot[thread_recycle_stack_count++] = stack;
        return;
    }
#endif
    ruby_xfree(stack);
}

#ifdef USE_THREAD_RECYCLE
static rb_thread_t *
thread_recycle_struct(void)
{
    void *p = ALLOC_N(rb_thread_t, 1);
    memset(p, 0, sizeof(rb_thread_t));
    return p;
}
#endif

void
rb_thread_mark(void *ptr)
{
    rb_thread_t *th = NULL;
    RUBY_MARK_ENTER("thread");
    if (ptr) {
        th = ptr;
        if (th->stack) {
            VALUE *p = th->stack;
            VALUE *sp = th->cfp->sp;
            rb_control_frame_t *cfp = th->cfp;
            rb_control_frame_t *limit_cfp = (void *)(th->stack + th->stack_size);

            while (p < sp) {
                rb_gc_mark(*p++);
            }
            rb_gc_mark_locations(p, p + th->mark_stack_len);

            while (cfp != limit_cfp) {
                rb_iseq_t *iseq = cfp->iseq;
                rb_gc_mark(cfp->proc);
                rb_gc_mark(cfp->self);
                if (iseq) {
                    rb_gc_mark(RUBY_VM_NORMAL_ISEQ_P(iseq) ? iseq->self : (VALUE)iseq);
                }
                if (cfp->me) ((rb_method_entry_t *)cfp->me)->mark = 1;
                cfp = RUBY_VM_PREVIOUS_CONTROL_FRAME(cfp);
            }
        }

        /* mark ruby objects */
        RUBY_MARK_UNLESS_NULL(th->first_proc);
        if (th->first_proc) RUBY_MARK_UNLESS_NULL(th->first_args);

        RUBY_MARK_UNLESS_NULL(th->thgroup);
        RUBY_MARK_UNLESS_NULL(th->value);
        RUBY_MARK_UNLESS_NULL(th->errinfo);
        RUBY_MARK_UNLESS_NULL(th->thrown_errinfo);
        RUBY_MARK_UNLESS_NULL(th->local_svar);
        RUBY_MARK_UNLESS_NULL(th->top_self);
        RUBY_MARK_UNLESS_NULL(th->top_wrapper);
        RUBY_MARK_UNLESS_NULL(th->fiber);
        RUBY_MARK_UNLESS_NULL(th->root_fiber);
        RUBY_MARK_UNLESS_NULL(th->stat_insn_usage);
        RUBY_MARK_UNLESS_NULL(th->last_status);

        RUBY_MARK_UNLESS_NULL(th->locking_mutex);

        rb_mark_tbl(th->local_storage);

        if (GET_THREAD() != th && th->machine_stack_start && th->machine_stack_end) {
            rb_gc_mark_machine_stack(th);
            rb_gc_mark_locations((VALUE *)&th->machine_regs,
                                 (VALUE *)(&th->machine_regs) +
                                 sizeof(th->machine_regs) / sizeof(VALUE));
        }

        mark_event_hooks(th->event_hooks);
    }

    RUBY_MARK_LEAVE("thread");
}

static void
thread_free(void *ptr)
{
    rb_thread_t *th;
    RUBY_FREE_ENTER("thread");

    if (ptr) {
        th = ptr;

        if (!th->root_fiber) {
            RUBY_FREE_UNLESS_NULL(th->stack);
        }

        if (th->locking_mutex != Qfalse) {
            rb_bug("thread_free: locking_mutex must be NULL (%p:%p)", (void *)th, (void *)th->locking_mutex);
        }
        if (th->keeping_mutexes != NULL) {
            rb_bug("thread_free: keeping_mutexes must be NULL (%p:%p)", (void *)th, (void *)th->keeping_mutexes);
        }

        if (th->local_storage) {
            st_free_table(th->local_storage);
        }

        if (th->vm && th->vm->main_thread == th) {
            RUBY_GC_INFO("main thread\n");
        }
        else {
#ifdef USE_SIGALTSTACK
            if (th->altstack) {
                free(th->altstack);
            }
#endif
            ruby_xfree(ptr);
        }
        if (ruby_current_thread == th)
            ruby_current_thread = NULL;
    }
    RUBY_FREE_LEAVE("thread");
}

static size_t
thread_memsize(const void *ptr)
{
    if (ptr) {
        const rb_thread_t *th = ptr;
        size_t size = sizeof(rb_thread_t);

        if (!th->root_fiber) {
            size += th->stack_size * sizeof(VALUE);
        }
        if (th->local_storage) {
            size += st_memsize(th->local_storage);
        }
        return size;
    }
    else {
        return 0;
    }
}

#define thread_data_type ruby_threadptr_data_type
const rb_data_type_t ruby_threadptr_data_type = {
    "VM/thread",
    {
        rb_thread_mark,
        thread_free,
        thread_memsize,
    },
};

VALUE
rb_obj_is_thread(VALUE obj)
{
    if (rb_typeddata_is_kind_of(obj, &thread_data_type)) {
        return Qtrue;
    }
    else {
        return Qfalse;
    }
}

static VALUE
thread_alloc(VALUE klass)
{
    VALUE volatile obj;
#ifdef USE_THREAD_RECYCLE
    rb_thread_t *th = thread_recycle_struct();
    obj = TypedData_Wrap_Struct(klass, &thread_data_type, th);
#else
    rb_thread_t *th;
    obj = TypedData_Make_Struct(klass, rb_thread_t, &thread_data_type, th);
#endif
    return obj;
}

static void
th_init(rb_thread_t *th, VALUE self)
{
    th->self = self;

    /* allocate thread stack */
#ifdef USE_SIGALTSTACK
    /* altstack of main thread is reallocated in another place */
    th->altstack = malloc(ALT_STACK_SIZE);
#endif
    th->stack_size = RUBY_VM_THREAD_STACK_SIZE;
    th->stack = thread_recycle_stack(th->stack_size);

    th->cfp = (void *)(th->stack + th->stack_size);

    vm_push_frame(th, 0, VM_FRAME_MAGIC_TOP, Qnil, 0, 0,
                  th->stack, 0, 1);

    th->status = THREAD_RUNNABLE;
    th->errinfo = Qnil;
    th->last_status = Qnil;
    th->waiting_fd = -1;
}

static VALUE
ruby_thread_init(VALUE self)
{
    rb_thread_t *th;
    rb_vm_t *vm = GET_THREAD()->vm;
    GetThreadPtr(self, th);

    th_init(th, self);
    th->vm = vm;

    th->top_wrapper = 0;
    th->top_self = rb_vm_top_self();
    return self;
}

VALUE
rb_thread_alloc(VALUE klass)
{
    VALUE self = thread_alloc(klass);
    ruby_thread_init(self);
    return self;
}

static void
vm_define_method(rb_thread_t *th, VALUE obj, ID id, VALUE iseqval,
                 rb_num_t is_singleton, NODE *cref)
{
    VALUE klass = cref->nd_clss;
    int noex = (int)cref->nd_visi;
    rb_iseq_t *miseq;
    GetISeqPtr(iseqval, miseq);

    if (miseq->klass) {
        iseqval = rb_iseq_clone(iseqval, 0);
        RB_GC_GUARD(iseqval);
        GetISeqPtr(iseqval, miseq);
    }

    if (NIL_P(klass)) {
        rb_raise(rb_eTypeError, "no class/module to add method");
    }

    if (is_singleton) {
        if (FIXNUM_P(obj) || SYMBOL_P(obj)) {
            rb_raise(rb_eTypeError,
                     "can't define singleton method \"%s\" for %s",
                     rb_id2name(id), rb_obj_classname(obj));
        }

        rb_check_frozen(obj);
        klass = rb_singleton_class(obj);
        noex = NOEX_PUBLIC;
    }

    /* dup */
    COPY_CREF(miseq->cref_stack, cref);
    miseq->cref_stack->nd_visi = NOEX_PUBLIC;
    miseq->klass = klass;
    miseq->defined_method_id = id;
    rb_add_method(klass, id, VM_METHOD_TYPE_ISEQ, miseq, noex);

    if (!is_singleton && noex == NOEX_MODFUNC) {
        rb_add_method(rb_singleton_class(klass), id, VM_METHOD_TYPE_ISEQ, miseq, NOEX_PUBLIC);
    }
    INC_VM_STATE_VERSION();
}

#define REWIND_CFP(expr) do { \
    rb_thread_t *th__ = GET_THREAD(); \
    th__->cfp++; expr; th__->cfp--; \
} while (0)

static VALUE
m_core_define_method(VALUE self, VALUE cbase, VALUE sym, VALUE iseqval)
{
    REWIND_CFP({
        vm_define_method(GET_THREAD(), cbase, SYM2ID(sym), iseqval, 0, rb_vm_cref());
    });
    return Qnil;
}

static VALUE
m_core_define_singleton_method(VALUE self, VALUE cbase, VALUE sym, VALUE iseqval)
{
    REWIND_CFP({
        vm_define_method(GET_THREAD(), cbase, SYM2ID(sym), iseqval, 1, rb_vm_cref());
    });
    return Qnil;
}

static VALUE
m_core_set_method_alias(VALUE self, VALUE cbase, VALUE sym1, VALUE sym2)
{
    REWIND_CFP({
        rb_alias(cbase, SYM2ID(sym1), SYM2ID(sym2));
    });
    return Qnil;
}

static VALUE
m_core_set_variable_alias(VALUE self, VALUE sym1, VALUE sym2)
{
    REWIND_CFP({
        rb_alias_variable(SYM2ID(sym1), SYM2ID(sym2));
    });
    return Qnil;
}

static VALUE
m_core_undef_method(VALUE self, VALUE cbase, VALUE sym)
{
    REWIND_CFP({
        rb_undef(cbase, SYM2ID(sym));
        INC_VM_STATE_VERSION();
    });
    return Qnil;
}

static VALUE
m_core_set_postexe(VALUE self, VALUE iseqval)
{
    REWIND_CFP({
        rb_iseq_t *blockiseq;
        rb_block_t *blockptr;
        rb_thread_t *th = GET_THREAD();
        rb_control_frame_t *cfp = rb_vm_get_ruby_level_next_cfp(th, th->cfp);
        VALUE proc;

        if (cfp == 0) {
            rb_bug("m_core_set_postexe: unreachable");
        }

        GetISeqPtr(iseqval, blockiseq);

        blockptr = RUBY_VM_GET_BLOCK_PTR_IN_CFP(cfp);
        blockptr->iseq = blockiseq;
        blockptr->proc = 0;

        proc = rb_vm_make_proc(th, blockptr, rb_cProc);
        rb_set_end_proc(rb_call_end_proc, proc);
    });
    return Qnil;
}

extern VALUE *rb_gc_stack_start;
extern size_t rb_gc_stack_maxsize;
#ifdef __ia64
extern VALUE *rb_gc_register_stack_start;
#endif

/* debug functions */

/* :nodoc: */
static VALUE
sdr(void)
{
    rb_vm_bugreport();
    return Qnil;
}

/* :nodoc: */
static VALUE
nsdr(void)
{
    VALUE ary = rb_ary_new();
#if HAVE_BACKTRACE
#include <execinfo.h>
#define MAX_NATIVE_TRACE 1024
    static void *trace[MAX_NATIVE_TRACE];
    int n = backtrace(trace, MAX_NATIVE_TRACE);
    char **syms = backtrace_symbols(trace, n);
    int i;

    if (syms == 0) {
        rb_memerror();
    }

    for (i=0; i<n; i++) {
        rb_ary_push(ary, rb_str_new2(syms[i]));
    }
    free(syms); /* OK */
#endif
    return ary;
}

void
Init_VM(void)
{
    VALUE opts;
    VALUE klass;
    VALUE fcore;

    /* ::VM */
    rb_cRubyVM = rb_define_class("RubyVM", rb_cObject);
    rb_undef_alloc_func(rb_cRubyVM);
    rb_undef_method(CLASS_OF(rb_cRubyVM), "new");

    /* ::VM::FrozenCore */
    fcore = rb_class_new(rb_cBasicObject);
    RBASIC(fcore)->flags = T_ICLASS;
    klass = rb_singleton_class(fcore);
    rb_define_method_id(klass, id_core_set_method_alias, m_core_set_method_alias, 3);
    rb_define_method_id(klass, id_core_set_variable_alias, m_core_set_variable_alias, 2);
    rb_define_method_id(klass, id_core_undef_method, m_core_undef_method, 2);
    rb_define_method_id(klass, id_core_define_method, m_core_define_method, 3);
    rb_define_method_id(klass, id_core_define_singleton_method, m_core_define_singleton_method, 3);
    rb_define_method_id(klass, id_core_set_postexe, m_core_set_postexe, 1);
    rb_obj_freeze(fcore);
    rb_gc_register_mark_object(fcore);
    rb_mRubyVMFrozenCore = fcore;

    /* ::VM::Env */
    rb_cEnv = rb_define_class_under(rb_cRubyVM, "Env", rb_cObject);
    rb_undef_alloc_func(rb_cEnv);
    rb_undef_method(CLASS_OF(rb_cEnv), "new");

    /* ::Thread */
    rb_cThread = rb_define_class("Thread", rb_cObject);
    rb_undef_alloc_func(rb_cThread);

    /* ::VM::USAGE_ANALYSIS_* */
    rb_define_const(rb_cRubyVM, "USAGE_ANALYSIS_INSN", rb_hash_new());
    rb_define_const(rb_cRubyVM, "USAGE_ANALYSIS_REGS", rb_hash_new());
    rb_define_const(rb_cRubyVM, "USAGE_ANALYSIS_INSN_BIGRAM", rb_hash_new());
    rb_define_const(rb_cRubyVM, "OPTS", opts = rb_ary_new());

#if   OPT_DIRECT_THREADED_CODE
    rb_ary_push(opts, rb_str_new2("direct threaded code"));
#elif OPT_TOKEN_THREADED_CODE
    rb_ary_push(opts, rb_str_new2("token threaded code"));
#elif OPT_CALL_THREADED_CODE
    rb_ary_push(opts, rb_str_new2("call threaded code"));
#endif

#if OPT_STACK_CACHING
    rb_ary_push(opts, rb_str_new2("stack caching"));
#endif
#if OPT_OPERANDS_UNIFICATION
    rb_ary_push(opts, rb_str_new2("operands unification]"));
#endif
#if OPT_INSTRUCTIONS_UNIFICATION
    rb_ary_push(opts, rb_str_new2("instructions unification"));
#endif
#if OPT_INLINE_METHOD_CACHE
    rb_ary_push(opts, rb_str_new2("inline method cache"));
#endif
#if OPT_BLOCKINLINING
    rb_ary_push(opts, rb_str_new2("block inlining"));
#endif

    /* ::VM::InsnNameArray */
    rb_define_const(rb_cRubyVM, "INSTRUCTION_NAMES", rb_insns_name_array());

    /* debug functions ::VM::SDR(), ::VM::NSDR() */
#if VMDEBUG
    rb_define_singleton_method(rb_cRubyVM, "SDR", sdr, 0);
    rb_define_singleton_method(rb_cRubyVM, "NSDR", nsdr, 0);
#else
    (void)sdr;
    (void)nsdr;
#endif

    /* VM bootstrap: phase 2 */
    {
        rb_vm_t *vm = ruby_current_vm;
        rb_thread_t *th = GET_THREAD();
        VALUE filename = rb_str_new2("<main>");
        volatile VALUE iseqval = rb_iseq_new(0, filename, filename, Qnil, 0, ISEQ_TYPE_TOP);
        volatile VALUE th_self;
        rb_iseq_t *iseq;

        /* create vm object */
        vm->self = TypedData_Wrap_Struct(rb_cRubyVM, &vm_data_type, vm);

        /* create main thread */
        th_self = th->self = TypedData_Wrap_Struct(rb_cThread, &thread_data_type, th);
        vm->main_thread = th;
        vm->running_thread = th;
        th->vm = vm;
        th->top_wrapper = 0;
        th->top_self = rb_vm_top_self();
        rb_thread_set_current(th);

        vm->living_threads = st_init_numtable();
        st_insert(vm->living_threads, th_self, (st_data_t) th->thread_id);

        rb_gc_register_mark_object(iseqval);
        GetISeqPtr(iseqval, iseq);
        th->cfp->iseq = iseq;
        th->cfp->pc = iseq->iseq_encoded;
        th->cfp->self = th->top_self;

        /*
         * The Binding of the top level scope
         */
        rb_define_global_const("TOPLEVEL_BINDING", rb_binding_new());
    }
    vm_init_redefined_flag();
}

void
rb_vm_set_progname(VALUE filename)
{
    rb_thread_t *th = GET_VM()->main_thread;
    rb_control_frame_t *cfp = (void *)(th->stack + th->stack_size);
    --cfp;
    cfp->iseq->filename = filename;
}

#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
struct rb_objspace *rb_objspace_alloc(void);
#endif

void
Init_BareVM(void)
{
    /* VM bootstrap: phase 1 */
    rb_vm_t * vm = malloc(sizeof(*vm));
    rb_thread_t * th = malloc(sizeof(*th));
    if (!vm || !th) {
        fprintf(stderr, "[FATAL] failed to allocate memory\n");
        exit(EXIT_FAILURE);
    }
    MEMZERO(th, rb_thread_t, 1);

    rb_thread_set_current_raw(th);

    vm_init2(vm);
#if defined(ENABLE_VM_OBJSPACE) && ENABLE_VM_OBJSPACE
    vm->objspace = rb_objspace_alloc();
#endif
    ruby_current_vm = vm;

    Init_native_thread();
    th_init(th, 0);
    th->vm = vm;
    ruby_thread_init_stack(th);
}

/* top self */

static VALUE
main_to_s(VALUE obj)
{
    return rb_str_new2("main");
}

VALUE
rb_vm_top_self(void)
{
    return GET_VM()->top_self;
}

void
Init_top_self(void)
{
    rb_vm_t *vm = GET_VM();

    vm->top_self = rb_obj_alloc(rb_cObject);
    rb_define_singleton_method(rb_vm_top_self(), "to_s", main_to_s, 0);

    /* initialize mark object array */
    vm->mark_object_ary = rb_ary_tmp_new(1);
}

VALUE *
ruby_vm_verbose_ptr(rb_vm_t *vm)
{
    return &vm->verbose;
}

VALUE *
ruby_vm_debug_ptr(rb_vm_t *vm)
{
    return &vm->debug;
}

VALUE *
rb_ruby_verbose_ptr(void)
{
    return ruby_vm_verbose_ptr(GET_VM());
}

VALUE *
rb_ruby_debug_ptr(void)
{
    return ruby_vm_debug_ptr(GET_VM());
}

---