engine.cpp

UC Library Extensions UnderC comes with a pocket implementation of the standard C++ libraries, wh

/* ENGINE.CPP
 * The stackcode engine
 * UnderC C++ interpreter
 * Steve Donovan, 2001
 * This is GPL'd software, and the usual disclaimers apply.
 * See LICENCE
 */
#include "classlib.h"
#include <list>
#include <memory.h>
#include "stack.h"
#include "opcodes.h"
#include "directcall.h"
#include "hard_except.h"
#include "breakpoints.h"
#include "common.h"
#include "errors.h"
#include "program.h"
#include "loaded_module_list.h"

int lo_byte(int data)
{
   return data & 0xFF;
}

int hi_byte(int data)
{
	return (data & 0xFF00) >> 8;
}

// *change 1.2.2 Switch off ODS debugging by default in debug mode
#ifdef _DEBUG
//#define DEBUG_ODS
//#define TRACK_ODS
extern int gDebugBreak;
extern FBlock* gFunBlock;
void __break(int);
 void check_fun_block(FBlock* fb)
 {
  if (gFunBlock == fb)
      __break(3);
 }
#else
#define check_fun_block(x)
#endif

// *change 1.2.3 We now by default put all global objects requiring destruction
// onto a static ODL, which is cleared at the end of the session.
// Uncomment the next line if you don't want this!
// #define NO_STATIC_ODS

// from common.cpp
void unpack_bitfield(int data, int& offs, int& bit_offs, int& bit_size);

CEXPORT char *sh_fun();  // debug function

// later in this file....
int current_ip();  
void  exec_message(char *msg, bool was_error, bool dont_unwind = false);
bool get_curent_exec_pos(int& ip_offs, string& fname,  LineInfo& li);
int get_current_exec_line();

namespace Builtin {
  PClass imported_class_from_function(void *pfn);
}

// useful macro for tracing...
#define OUT(v) cout << #v " = " << v << endl

const int ODS_STACKSIZE = 200, ODS_TEMP_BUFFSIZE = 400;
const int MAX_CODE_LEVELS = 2;
const int MAX_FUNCTION_DEPTH = 8000;
const int EXEC_STACKSIZE = 100000, OBJECT_STACKSIZE = 9000;
#define START_FB (FBlock *)0x0a

void
CodeGenerator::out(Instruction *is)
{
 *pcode = *is;
 pcode++;
 NC++;
 mTotal++;
}

void
CodeGenerator::emitc(int opc, RMode rm, int data)
//------------------------------------------
{
 pcode->opcode = opc;
 pcode->rmode  = rm;
 pcode->data   = data;
 pcode++;
 NC++;
 mTotal++;
}

int
CodeGenerator::total_instructions()
{ return mTotal; }

int
CodeGenerator::ip_offset()
{ return NC; }   // *because it counts instructions!*

Instruction *
CodeGenerator::current_pi()
{ return pcode; }


Instruction *
CodeGenerator::last_pi()
{ return pcode-1; }

void
CodeGenerator::begin_code()
{
 NC = 0;
}

void
CodeGenerator::backspace()
{
 pcode--;
 NC--;
 mTotal--;
}


Instruction *
CodeGenerator::end_code()
//---------------------
{
 if (NC) {
   pcode->opcode = 0; NC++; // flag end-of-code!
   Instruction *pi = new Instruction[NC];
   memcpy(pi,_code_buff_,sizeof(Instruction)*NC);
   pcode = _code_buff_;
   NC = 0;
   mTotal = 0;  // *fix 1.1.2 Was not reset
   return pi;
 } 
 else return NULL;
}

// *add 1.2.3a Returns non-NULL ptr to instruction if this function
// has exactly one instruction
Instruction* 
CodeGenerator::has_one_instruction(Function* pf)
{
  Instruction* ip = pf->fun_block()->pstart;
  // look past the RETx instruction to see the end-of-code marker
  if (ip && (ip+2)->opcode == 0) return ip;
  else return NULL;
}

Instruction *
CodeGenerator::instruction_with_pointer(int opcode, void *ptr)
{
    typedef void *pvoid;
    Instruction *pi = new Instruction();
    pi->opcode = opcode;
    pi->rmode = DIRECT;
    pi->data = Parser::global().alloc(sizeof(pvoid),NULL);
    *(pvoid *)Parser::global().addr(pi->data) = ptr;
    return pi;
}



Instruction *
x_copy_code(Instruction *iptr)
{
 Instruction *pi = iptr;
 while (pi->opcode != 0) pi++;
 int sz = ((int)pi - (int)iptr)/sizeof(Instruction);
 pi = new Instruction[sz];
 memcpy(pi,iptr,sizeof(Instruction)*sz);
 return pi;
}


const int FUNCTION_STACK_DEPTH = 3*MAX_FUNCTION_DEPTH;
static Stack<void *,FUNCTION_STACK_DEPTH> fs;
char *mDataSeg;
static char *mDataPtr = mDataSeg;

void Engine::set_data_seg(void *ptr)
{ mDataSeg = (char *)ptr; }

// for reasons of efficiency, the execution stack
// is statically allocated.  Fine if thread-safe isn't
// a piority.
// (note: I know this should be in an anonymous namespace,
// but the Visual C++ debugger can't see them then...until
// then!)
static bool ptr_check;
static int _stack_[EXEC_STACKSIZE];
static int *mSP = _stack_ + EXEC_STACKSIZE - 1;
static int *mEndStack = _stack_;

void reset_execution_stack()
{ // currently only called after stack overflow....
  mSP = _stack_ + EXEC_STACKSIZE - 1;
}

// double-word stack operations

inline void push(int val) {
    *(--mSP) = val;
}

inline int  pop() {
    return *(mSP++);
}

int popp() { // specialized pointer-checking pop!
  int p = pop();
  if (ptr_check) Builtin::bad_ptr_check((void *)p);
  return p;
}

inline int& tos() {
    return *mSP;
}

inline void drop() {
    ++mSP;
}

inline void pushf(float v) {
     *((float *)--mSP) = v;
}

inline float popf() { 
    return *((float *)mSP++);
}

// quadword stack operations

inline void push2(double fval) {
    mSP -= 2; *((double *)mSP) = fval; 
}

inline double pop2() {
	double tmp = *(double *)mSP; mSP += 2; return tmp;  
}

inline double& tos2() {
       return *(double *)mSP;
}

inline void   drop2() {
    mSP += 2;
}

int stack_depth() { return  (int)_stack_ - (int)mSP; }

void stack_report(ostream& os,int *base)
{
    os << "STACK: ";
    if (base == NULL) base = _stack_;
    if (base == mSP) { os << "(Empty)" << endl; return; }
    while (base != mSP-1) {
        os << *base++ << ' ';
    } 
    os << '(' << *base << ')' << endl;
}

int Engine::retval()
{  return tos(); }

//----------------------- object-stack ------------------------------------
static Stack<char *,OBJECT_STACKSIZE> ostack;
static char *mOP;

// these functions define the Virtual Method Table structure of UC

inline PFBlock virtual_method_lookup(int slot)
{
  return PFBlock( (*VMT(mOP))[slot] );
}

PFBlock virtual_method_imported_lookup(int slot)
{
// *add 1.2.0 Imported objects may have associated VMTs!
    return PFBlock( (Class::find_VMT(mOP))[slot] );
}

PClass get_class_object(void *p)
{
// *change 1.2.0 In general, dynamic casts need to look in the VMT map
// because objects may have been imported without a VMT in the usual position
    PPClass pc = Class::find_VMT(p);
    if (pc) return pc[0];
    else return (*VMT(p))[0];
}

PPClass& get_object_VMT(void* p)
{
   return *VMT(p);
}

inline void opop() 
{ 
  mOP = ostack.pop();
}

void chk_ods()
{
  if (ostack.depth() > OBJECT_STACKSIZE) 
       ostack.clear();

}

inline void opush(void *data)
{ 
    if (ptr_check) Builtin::bad_ptr_check(data);
    ostack.push(mOP);
    mOP = (char *)data;
}

inline char *otos()
{
  return ostack.TOS();
}

void Engine::object_ptr(void *data)
{
 mOP = (char *)data;
}

void *Engine::object_ptr()
{
 return mOP;
}

// potentially quite dubious - at the mo., only used so we can use JINC to move mOP
// for object array construction.
char **Engine::object_ptr_addr()
{
 return &mOP;
}

  
//----------------------- THE ACTUAL ENGINE ---------------------------------
Instruction *ppcode;
FBlock *fb;
int *baseSP;

struct ExecutionState {
  Instruction *m_ppcode;
  FBlock* m_fb;
  int *m_baseSP;
  bool m_cntxt_pushed;
  ArgBlock *m_xargs;  

  void save(Instruction *_ppcode, bool cpushed)
  { 
      m_ppcode = _ppcode;
      m_fb = fb; 
      m_baseSP = baseSP;
      m_cntxt_pushed = cpushed;
  }

  void restore(bool& cpushed, ArgBlock *&args)
  {
      ppcode = m_ppcode;
      fb = m_fb;
      baseSP = m_baseSP;
      cpushed = m_cntxt_pushed;
      args = m_xargs;
  }

};

ExecutionState resume_state;

const Instruction *end_of_code = (Instruction *)4;

//----------------------- object destructor stack ---------------------------
// *change 1.0.0 The ODS is now a stack of <class,object> records
// *change 1.2.3 The stack is now backed by a vector, so we don't get
// unpleasant suprises with large numbers of objects.

template <class T, int N>
class VStack {
private:
    std::vector<T> m_vec;
public:
    VStack()
    { m_vec.reserve(N); m_vec.resize(0);}

    void push(const T& val)
    {
      m_vec.push_back(val);
    }

    T pop()
    { 
      T val = m_vec.back();
      m_vec.pop_back();
      return val;
    }

    bool empty()
    { 
      return m_vec.size() = 0;
    }

    void clear()
    {
      m_vec.resize(0);
    }

    int depth()
    {
      return m_vec.size();
    }

    T& get(int i)
    { return m_vec[i]; }
};

struct ODS_Record {
  PClass m_class;
  void  *m_obj;
#ifdef DEBUG_ODS
  Function *m_fn;  //DEBUG fields
  int m_offs;
#endif