factor/vm/vm.hpp

using namespace std;

namespace factor {

typedef void (*c_to_factor_func_type)(cell quot);
typedef void (*unwind_native_frames_func_type)(cell quot, cell to);
typedef cell (*get_fpu_state_func_type)();
typedef void (*set_fpu_state_func_type)(cell state);

struct growable_array;
struct code_root;

struct factor_vm {
  //
  // vvvvvv
  // THESE FIELDS ARE ACCESSED DIRECTLY FROM FACTOR. See:
  //   basis/vm/vm.factor
  //   basis/compiler/constants/constants.factor

  // Current context
  context* ctx;

  // Spare context -- for callbacks
  context* spare_ctx;

  // New objects are allocated here, use the data->nursery reference
  // instead from c++ code.
  bump_allocator nursery;

  // Add this to a shifted address to compute write barrier offsets
  cell cards_offset;
  cell decks_offset;

  // cdecl signal handler address, used by signal handler subprimitives
  cell signal_handler_addr;

  // are we handling a memory error? used to detect double faults
  cell faulting_p;

  // Various special objects, accessed by special-object and
  // set-special-object primitives
  cell special_objects[special_object_count];

  // THESE FIELDS ARE ACCESSED DIRECTLY FROM FACTOR.
  // ^^^^^^
  //

  // Handle to the main thread we run in
  THREADHANDLE thread;

  // Data stack and retain stack sizes
  cell datastack_size, retainstack_size, callstack_size;

  // Stack of callback IDs
  std::vector<int> callback_ids;

  // Next callback ID
  int callback_id;

  // List of callback function descriptors for PPC
  std::list<void**> function_descriptors;

  // Pooling unused contexts to make context allocation cheaper
  std::list<context*> unused_contexts;

  // Active contexts, for tracing by the GC
  std::set<context*> active_contexts;

  // External entry points
  c_to_factor_func_type c_to_factor_func;

  // Is profiling enabled?
  volatile cell sampling_profiler_p;
  fixnum samples_per_second;

  // Global variables used to pass fault handler state from signal handler
  // to VM
  bool signal_resumable;
  cell signal_number;
  cell signal_fault_addr;
  cell signal_fault_pc;
  unsigned int signal_fpu_status;

  // Pipe used to notify Factor multiplexer of signals
  int signal_pipe_input, signal_pipe_output;

  // State kept by the sampling profiler
  std::vector<profiling_sample> samples;
  volatile profiling_sample current_sample;

  // GC is off during heap walking
  bool gc_off;

  // Data heap
  data_heap* data;

  // Code heap
  code_heap* code;

  // Pinned callback stubs
  callback_heap* callbacks;

  // Only set if we're performing a GC
  gc_state* current_gc;
  volatile cell current_gc_p;

  // Set if we're in the jit
  volatile fixnum current_jit_count;

  // Mark stack used for mark & sweep GC
  std::vector<cell> mark_stack;

  // If not NULL, we push GC events here
  std::vector<gc_event>* gc_events;

  // If a runtime function needs to call another function which potentially
  // allocates memory, it must wrap any references to the data and code
  // heaps with data_root and code_root smart pointers, which register
  // themselves here. See data_roots.hpp and code_roots.hpp

  std::vector<cell*> data_roots;
  std::vector<code_root*> code_roots;

  // Debugger
  bool fep_p;
  bool fep_help_was_shown;
  bool fep_disabled;
  bool full_output;

  // Method dispatch statistics
  dispatch_statistics dispatch_stats;

  // Number of entries in a polymorphic inline cache
  cell max_pic_size;

  // Incrementing object counter for identity hashing
  cell object_counter;

  // Sanity check to ensure that monotonic counter doesn't decrease
  uint64_t last_nano_count;

  // Stack for signal handlers, only used on Unix
  segment* signal_callstack_seg;

  // Are we already handling a fault? Used to catch double memory faults
  static bool fatal_erroring_p;

  // Two fep_p variants, one might be redundant.
  volatile cell safepoint_fep_p;

  // Allow Ctrl-Break a busy loop in the Listener, only used on Windows
  volatile bool stop_on_ctrl_break;

  // contexts
  context* new_context();
  void init_context(context* ctx);
  void delete_context();
  cell begin_callback(cell quot);
  void end_callback();
  void primitive_current_callback();
  void primitive_context_object();
  void primitive_context_object_for();
  void primitive_set_context_object();
  cell stack_to_array(cell bottom, cell top, vm_error_type error);
  cell datastack_to_array(context* ctx);
  void primitive_datastack_for();
  cell retainstack_to_array(context* ctx);
  void primitive_retainstack_for();
  void primitive_set_datastack();
  void primitive_set_retainstack();
  void primitive_check_datastack();
  void primitive_load_locals();

  // run
  void primitive_exit();
  void primitive_nano_count();
  void primitive_sleep();
  void primitive_set_slot();

  // objects
  void primitive_special_object();
  void primitive_set_special_object();
  void primitive_identity_hashcode();
  void primitive_compute_identity_hashcode();
  void primitive_clone();
  void primitive_become();

  // sampling_profiler
  void record_sample(bool prolog_p);
  void start_sampling_profiler(fixnum rate);
  void end_sampling_profiler();
  void set_sampling_profiler(fixnum rate);
  void primitive_sampling_profiler();
  void primitive_get_samples();
  array* allot_growarr();
  void growarr_add(array *growarr_, cell value);

  // errors
  void general_error(vm_error_type error, cell arg1, cell arg2);
  void type_error(cell type, cell tagged);
  void set_memory_protection_error(cell fault_addr, cell fault_pc);
  void divide_by_zero_error();

  // bignum
  int bignum_equal_p(bignum* x, bignum* y);
  enum bignum_comparison bignum_compare(bignum* x, bignum* y);
  bignum* bignum_add(bignum* x, bignum* y);
  bignum* bignum_subtract(bignum* x, bignum* y);
  bignum* bignum_square(bignum* x_);
  bignum* bignum_multiply(bignum* x, bignum* y);
  void bignum_divide(bignum* numerator, bignum* denominator, bignum** quotient,
                     bignum** remainder);
  bignum* bignum_quotient(bignum* numerator, bignum* denominator);
  bignum* bignum_remainder(bignum* numerator, bignum* denominator);
  fixnum bignum_to_fixnum_strict(bignum* bn);
  bignum* double_to_bignum(double x);
  int bignum_equal_p_unsigned(bignum* x, bignum* y);
  enum bignum_comparison bignum_compare_unsigned(bignum* x, bignum* y);
  bignum* bignum_add_unsigned(bignum* x_, bignum* y_, int negative_p);
  bignum* bignum_subtract_unsigned(bignum* x_, bignum* y_);
  bignum* bignum_multiply_unsigned(bignum* x_, bignum* y_, int negative_p);
  bignum* bignum_multiply_unsigned_small_factor(bignum* x, bignum_digit_type y,
                                                int negative_p);
  void bignum_destructive_add(bignum* bn, bignum_digit_type n);
  void bignum_destructive_scale_up(bignum* bn, bignum_digit_type factor);
  void bignum_divide_unsigned_large_denominator(
      bignum* numerator_, bignum* denominator_, bignum** quotient,
      bignum** remainder, int q_negative_p, int r_negative_p);
  void bignum_divide_unsigned_normalized(bignum* u, bignum* v, bignum* q);
  bignum_digit_type bignum_divide_subtract(bignum_digit_type* v_start,
                                           bignum_digit_type* v_end,
                                           bignum_digit_type guess,
                                           bignum_digit_type* u_start);
  void bignum_divide_unsigned_medium_denominator(
      bignum* numerator_, bignum_digit_type denominator, bignum** quotient,
      bignum** remainder, int q_negative_p, int r_negative_p);
  void bignum_destructive_normalization(bignum* source, bignum* target,
                                        int shift_left);
  void bignum_destructive_unnormalization(bignum* bn, int shift_right);
  bignum_digit_type bignum_digit_divide(
      bignum_digit_type uh, bignum_digit_type ul, bignum_digit_type v,
      bignum_digit_type* q); // return value
  bignum_digit_type bignum_digit_divide_subtract(bignum_digit_type v1,
                                                 bignum_digit_type v2,
                                                 bignum_digit_type guess,
                                                 bignum_digit_type* u);
  void bignum_divide_unsigned_small_denominator(
      bignum* numerator_, bignum_digit_type denominator, bignum** quotient,
      bignum** remainder, int q_negative_p, int r_negative_p);
  bignum_digit_type bignum_destructive_scale_down(
      bignum* bn, bignum_digit_type denominator);
  bignum* bignum_remainder_unsigned_small_denominator(bignum* n,
                                                      bignum_digit_type d,
                                                      int negative_p);
  bignum* bignum_digit_to_bignum(bignum_digit_type digit, int negative_p);
  bignum* allot_bignum(bignum_length_type length, int negative_p);
  bignum* allot_bignum_zeroed(bignum_length_type length, int negative_p);
  bignum* bignum_shorten_length(bignum* bn, bignum_length_type length);
  bignum* bignum_trim(bignum* bn);
  bignum* bignum_new_sign(bignum* x_, int negative_p);
  bignum* bignum_maybe_new_sign(bignum* x_, int negative_p);
  void bignum_destructive_copy(bignum* source, bignum* target);
  bignum* bignum_bitwise_not(bignum* x_);
  bignum* bignum_arithmetic_shift(bignum* arg1, fixnum n);
  bignum* bignum_bitwise_and(bignum* arg1, bignum* arg2);
  bignum* bignum_bitwise_ior(bignum* arg1, bignum* arg2);
  bignum* bignum_bitwise_xor(bignum* arg1, bignum* arg2);
  bignum* bignum_magnitude_ash(bignum* arg1_, fixnum n);
  bignum* bignum_pospos_bitwise_op(int op, bignum* arg1_, bignum* arg2_);
  bignum* bignum_posneg_bitwise_op(int op, bignum* arg1_, bignum* arg2_);
  bignum* bignum_negneg_bitwise_op(int op, bignum* arg1_, bignum* arg2_);
  void bignum_negate_magnitude(bignum* arg);
  bignum* bignum_integer_length(bignum* x_);
  int bignum_logbitp(int shift, bignum* arg);
  int bignum_unsigned_logbitp(int shift, bignum* bn);
  bignum* bignum_gcd(bignum* a_, bignum* b_);

  //data heap
  void set_data_heap(data_heap* data_);
  void primitive_size();
  data_heap_room data_room();
  void primitive_data_room();
  cell instances(cell type);
  void primitive_all_instances();

  template <typename Generation, typename Iterator>
  inline void each_object(Generation* gen, Iterator& iterator) {
    cell obj = gen->first_object();
    while (obj) {
      iterator((object*)obj);
      obj = gen->next_object_after(obj);
    }
  }

  template <typename Iterator> inline void each_object(Iterator& iterator) {

    // The nursery can't be iterated because there may be gaps between
    // the objects (see factor_vm::reallot_array) so we require it to
    // be empty first.
    FACTOR_ASSERT(data->nursery->occupied_space() == 0);

    gc_off = true;
    each_object(data->tenured, iterator);
    each_object(data->aging, iterator);
    gc_off = false;
  }

  template <typename Iterator>
  inline void each_object_each_slot(Iterator& iterator) {
    auto each_object_func = [&](object* obj) {
      auto each_slot_func = [&](cell* slot) {
        iterator(obj, slot);
      };
      obj->each_slot(each_slot_func);
    };
    each_object(each_object_func);
  }

  // the write barrier must be called any time we are potentially storing a
  // pointer from an older generation to a younger one
  inline void write_barrier(cell* slot_ptr) {
    *(unsigned char*)(cards_offset + ((cell)slot_ptr >> card_bits)) = card_mark_mask;
    *(unsigned char*)(decks_offset + ((cell)slot_ptr >> deck_bits)) = card_mark_mask;
  }

  inline void write_barrier(object* obj, cell size) {
    cell start = (cell)obj & (~card_size + 1);
    cell end = ((cell)obj + size + card_size - 1) & (~card_size + 1);

    for (cell offset = start; offset < end; offset += card_size)
      write_barrier((cell*)offset);
  }

  // data heap checker
  void check_data_heap();

  // gc
  void set_current_gc_op(gc_op op);
  void start_gc_again();
  void collect_nursery();
  void collect_aging();
  void collect_to_tenured();
  void update_code_roots_for_compaction();
  void collect_mark_impl();
  void collect_sweep_impl();
  void collect_full();
  void collect_compact_impl();
  void collect_compact();
  void collect_growing_data_heap(cell requested_size);
  void gc(gc_op op, cell requested_size);
  void primitive_minor_gc();
  void primitive_full_gc();
  void primitive_compact_gc();
  void primitive_enable_gc_events();
  void primitive_disable_gc_events();
  object* allot_object(cell type, cell size);
  object* allot_large_object(cell type, cell size);

  // Allocates memory
  template <typename Type> Type* allot(cell size) {
    return (Type*)allot_object(Type::type_number, size);
  }

  // generic arrays
  template <typename Array> Array* allot_uninitialized_array(cell capacity);
  template <typename Array>
  bool reallot_array_in_place_p(Array* array, cell capacity);
  template <typename Array> Array* reallot_array(Array* array_, cell capacity);

  // debug
  void print_chars(ostream& out, string* str);
  void print_word(ostream& out, word* word, cell nesting);
  void print_factor_string(ostream& out, string* str);
  void print_array(ostream& out, array* array, cell nesting);
  void print_byte_array(ostream& out, byte_array* array, cell nesting);
  void print_tuple(ostream& out, tuple* tuple, cell nesting);
  void print_alien(ostream& out, alien* alien, cell nesting);
  void print_nested_obj(ostream& out, cell obj, fixnum nesting);
  void print_obj(ostream& out, cell obj);
  void print_objects(ostream& out, cell* start, cell* end);
  void print_datastack(ostream& out);
  void print_retainstack(ostream& out);
  void print_callstack(ostream& out);
  void print_callstack_object(ostream& out, callstack* obj);
  void dump_cell(ostream& out, cell x);
  void dump_memory(ostream& out, cell from, cell to);
  void dump_memory_layout(ostream& out);
  void dump_objects(ostream& out, cell type);
  void dump_edges(ostream& out);
  void find_data_references(ostream& out, cell look_for_);
  void dump_code_heap(ostream& out);
  void factorbug_usage(bool advanced_p);
  void factorbug();
  void primitive_die();
  void primitive_enable_ctrl_break();
  void primitive_disable_ctrl_break();

  // arrays
  inline void set_array_nth(array* array, cell slot, cell value);
  array* allot_array(cell capacity, cell fill_);
  void primitive_array();
  cell allot_array_4(cell v1_, cell v2_, cell v3_, cell v4_);
  void primitive_resize_array();
  cell std_vector_to_array(std::vector<cell>& elements);

  // strings
  string* allot_string_internal(cell capacity);
  void fill_string(string* str_, cell start, cell capacity, cell fill);
  string* allot_string(cell capacity, cell fill);
  void primitive_string();
  bool reallot_string_in_place_p(string* str, cell capacity);
  string* reallot_string(string* str_, cell capacity);
  void primitive_resize_string();
  void primitive_set_string_nth_fast();

  // booleans
  cell tag_boolean(cell untagged) {
    return untagged ? special_objects[OBJ_CANONICAL_TRUE] : false_object;
  }

  // byte arrays
  byte_array* allot_byte_array(cell size);
  void primitive_byte_array();
  void primitive_uninitialized_byte_array();
  void primitive_resize_byte_array();

  template <typename Type> byte_array* byte_array_from_value(Type* value);

  // tuples
  void primitive_tuple();
  void primitive_tuple_boa();

  // words
  word* allot_word(cell name_, cell vocab_, cell hashcode_);
  void primitive_word();
  void primitive_word_code();
  void primitive_word_optimized_p();
  void primitive_wrapper();
  void jit_compile_word(cell word_, cell def_, bool relocating);

  // math
  void primitive_bignum_to_fixnum();
  void primitive_bignum_to_fixnum_strict();
  void primitive_float_to_fixnum();
  void primitive_fixnum_divint();
  void primitive_fixnum_divmod();
  bignum* fixnum_to_bignum(fixnum);
  bignum* cell_to_bignum(cell);
  bignum* long_long_to_bignum(int64_t n);
  bignum* ulong_long_to_bignum(uint64_t n);
  inline fixnum sign_mask(fixnum x);
  inline fixnum branchless_max(fixnum x, fixnum y);
  inline fixnum branchless_abs(fixnum x);
  void primitive_fixnum_shift();
  void primitive_fixnum_to_bignum();
  void primitive_float_to_bignum();
  void primitive_bignum_eq();
  void primitive_bignum_add();
  void primitive_bignum_subtract();
  void primitive_bignum_multiply();
  void primitive_bignum_divint();
  void primitive_bignum_divmod();
  void primitive_bignum_mod();
  void primitive_bignum_gcd();
  void primitive_bignum_and();
  void primitive_bignum_or();
  void primitive_bignum_xor();
  void primitive_bignum_shift();
  void primitive_bignum_less();
  void primitive_bignum_lesseq();
  void primitive_bignum_greater();
  void primitive_bignum_greatereq();
  void primitive_bignum_not();
  void primitive_bignum_bitp();
  void primitive_bignum_log2();
  inline cell unbox_array_size();
  void primitive_fixnum_to_float();
  void primitive_format_float();
  void primitive_float_eq();
  void primitive_float_add();
  void primitive_float_subtract();
  void primitive_float_multiply();
  void primitive_float_divfloat();
  void primitive_float_less();
  void primitive_float_lesseq();
  void primitive_float_greater();
  void primitive_float_greatereq();
  void primitive_float_bits();
  void primitive_bits_float();
  void primitive_double_bits();
  void primitive_bits_double();
  fixnum to_fixnum(cell tagged);
  fixnum to_fixnum_strict(cell tagged);
  cell to_cell(cell tagged);
  cell from_signed_8(int64_t n);
  int64_t to_signed_8(cell obj);
  cell from_unsigned_8(uint64_t n);
  uint64_t to_unsigned_8(cell obj);
  float to_float(cell value);
  double to_double(cell value);
  inline void overflow_fixnum_add(fixnum x, fixnum y);
  inline void overflow_fixnum_subtract(fixnum x, fixnum y);
  inline void overflow_fixnum_multiply(fixnum x, fixnum y);
  inline cell from_signed_cell(fixnum x);
  inline cell from_unsigned_cell(cell x);
  inline cell allot_float(double n);
  inline bignum* float_to_bignum(cell tagged);
  inline double untag_float(cell tagged);
  inline double untag_float_check(cell tagged);
  inline fixnum float_to_fixnum(cell tagged);
  inline double fixnum_to_float(cell tagged);

  // tagged
  template <typename Type> void check_tagged(tagged<Type> t) {
    if (!t.type_p())
      type_error(Type::type_number, t.value_);
  }

  template <typename Type> Type* untag_check(cell value) {
    tagged<Type> t(value);
    check_tagged(t);
    return t.untagged();
  }

  // io
  void io_error_if_not_EINTR();
  FILE* safe_fopen(char* filename, const char* mode);
  int safe_fgetc(FILE* stream);
  size_t safe_fread(void* ptr, size_t size, size_t nitems, FILE* stream);
  void safe_fputc(int c, FILE* stream);
  size_t safe_fwrite(void* ptr, size_t size, size_t nitems, FILE* stream);
  int safe_ftell(FILE* stream);
  void safe_fseek(FILE* stream, off_t offset, int whence);
  void safe_fflush(FILE* stream);
  void primitive_fopen();
  FILE* pop_file_handle();
  FILE* peek_file_handle();
  void primitive_fgetc();
  void primitive_fread();
  void primitive_fputc();
  void primitive_fwrite();
  void primitive_ftell();
  void primitive_fseek();
  void primitive_fflush();
  void primitive_fclose();

  // code_block
  cell compute_entry_point_pic_address(word* w, cell tagged_quot);
  cell compute_entry_point_pic_address(cell w_);
  cell compute_entry_point_pic_tail_address(cell w_);
  cell compute_external_address(instruction_operand op);

  void update_word_references(code_block* compiled, bool reset_inline_caches);
  void undefined_symbol();
  cell compute_dlsym_address(array* literals, cell index, bool toc);
  cell lookup_external_address(relocation_type rel_type,
                               code_block* compiled,
                               array* parameters,
                               cell index);
  void initialize_code_block(code_block* compiled, cell literals);
  void initialize_code_block(code_block* compiled);
  void fixup_labels(array* labels, code_block* compiled);
  code_block* allot_code_block(cell size, code_block_type type);
  code_block* add_code_block(code_block_type type, cell code_, cell labels_,
                             cell owner_, cell relocation_, cell parameters_,
                             cell literals_, cell frame_size_untagged);

  //code heap
  template <typename Iterator> void each_code_block(Iterator& iter) {
    code->allocator->iterate(iter, no_fixup());
  }

  void update_code_heap_words(bool reset_inline_caches);
  void primitive_modify_code_heap();
  void primitive_code_room();
  void primitive_strip_stack_traces();
  void primitive_code_blocks();

  // callbacks
  void primitive_free_callback();
  void primitive_callback();
  void primitive_callback_room();

  // image
  void load_data_heap(FILE* file, image_header* h, vm_parameters* p);
  void load_code_heap(FILE* file, image_header* h, vm_parameters* p);
  bool save_image(const vm_char* saving_filename, const vm_char* filename);
  void primitive_save_image();
  void fixup_heaps(cell data_offset, cell code_offset);
  void load_image(vm_parameters* p);
  bool read_embedded_image_footer(FILE* file, embedded_image_footer* footer);
  bool embedded_image_p();

  template <typename Iterator, typename Fixup>
  void iterate_callstack_object(callstack* stack_, Iterator& iterator,
                                Fixup& fixup);
  template <typename Iterator>
  void iterate_callstack_object(callstack* stack_, Iterator& iterator);

  callstack* allot_callstack(cell size);
  cell second_from_top_stack_frame(context* ctx);
  cell capture_callstack(context* ctx);
  void primitive_callstack_for();
  void primitive_callstack_to_array();
  void primitive_innermost_stack_frame_executing();
  void primitive_innermost_stack_frame_scan();
  void primitive_set_innermost_stack_frame_quotation();
  void primitive_callstack_bounds();

  template <typename Iterator, typename Fixup>
  void iterate_callstack(context* ctx, Iterator& iterator, Fixup& fixup);
  template <typename Iterator>
  void iterate_callstack(context* ctx, Iterator& iterator);

  // cpu-*
  void dispatch_signal_handler(cell* sp, cell* pc, cell newpc);
#if defined(FACTOR_X86) || defined(FACTOR_64)
  void dispatch_non_resumable_signal(cell* sp, cell* pc,
                                     cell handler,
                                     cell limit);
  void dispatch_resumable_signal(cell* sp, cell* pc, cell handler);
#endif

  // alien
  char* pinned_alien_offset(cell obj);
  cell allot_alien(cell delegate_, cell displacement);
  cell allot_alien(cell address);
  void primitive_displaced_alien();
  void primitive_alien_address();
  void* alien_pointer();
  void primitive_dlopen();
  void primitive_dlsym();
  void primitive_dlsym_raw();
  void primitive_dlclose();
  void primitive_dll_validp();
  char* alien_offset(cell obj);

  // quotations
  void primitive_jit_compile();
  cell lazy_jit_compile_entry_point();
  void primitive_array_to_quotation();
  void primitive_quotation_code();
  code_block* jit_compile_quotation(cell owner_, cell quot_, bool relocating);
  void jit_compile_quotation(cell quot_, bool relocating);
  fixnum quot_code_offset_to_scan(cell quot_, cell offset);
  cell lazy_jit_compile(cell quot);
  bool quotation_compiled_p(quotation* quot);
  void primitive_quotation_compiled_p();

  // dispatch
  cell lookup_tuple_method(cell obj, cell methods);
  cell lookup_method(cell obj, cell methods);
  void primitive_lookup_method();
  cell object_class(cell obj);
  void update_method_cache(cell cache, cell klass, cell method);
  void primitive_mega_cache_miss();
  void primitive_reset_dispatch_stats();
  void primitive_dispatch_stats();

  // inline cache
  void deallocate_inline_cache(cell return_address);
  void update_pic_count(cell type);
  cell add_inline_cache_entry(cell cache_entries_, cell klass_, cell method_);
  void update_pic_transitions(cell pic_size);
  cell inline_cache_miss(cell return_address);

  // entry points
  void c_to_factor(cell quot);
  void unwind_native_frames(cell quot, cell to);
  cell get_fpu_state();
  void set_fpu_state(cell state);

  // safepoints
  void handle_safepoint(cell pc);
  void enqueue_samples(cell samples, cell pc, bool foreign_thread_p);
  void enqueue_fep();

  // factor
  void prepare_boot_image();
  void init_factor(vm_parameters* p);
  void pass_args_to_factor(int argc, vm_char** argv);
  void stop_factor();
  void start_standalone_factor(int argc, vm_char** argv);
  char* factor_eval_string(char* string);
  void factor_eval_free(char* result);
  void factor_yield();
  void factor_sleep(long us);

  // os-*
  void primitive_existsp();
  void init_ffi();
  void ffi_dlopen(dll* dll);
  cell ffi_dlsym(dll* dll, symbol_char* symbol);
  cell ffi_dlsym_raw(dll* dll, symbol_char* symbol);
  void ffi_dlclose(dll* dll);
  void c_to_factor_toplevel(cell quot);
  void init_signals();
  void start_sampling_profiler_timer();
  void end_sampling_profiler_timer();

// os-windows
#if defined(WINDOWS)
  /* Id of the main thread we run in. Used for Ctrl-Break handling. */
  DWORD thread_id;

  HANDLE ctrl_break_thread;

  HANDLE sampler_thread;
  void sampler_thread_loop();

  const vm_char* vm_executable_path();
  const vm_char* default_image_path();
  BOOL windows_stat(vm_char* path);

  LONG exception_handler(PEXCEPTION_RECORD e, void* frame, PCONTEXT c,
                         void* dispatch);

#else  // UNIX
  void dispatch_signal(void* uap, void(handler)());
  void unix_init_signals();
#endif

#ifdef __APPLE__
  void call_fault_handler(exception_type_t exception,
                          exception_data_type_t code,
                          MACH_EXC_STATE_TYPE* exc_state,
                          MACH_THREAD_STATE_TYPE* thread_state,
                          MACH_FLOAT_STATE_TYPE* float_state);
#endif

  factor_vm(THREADHANDLE thread_id);
  ~factor_vm();
};

}