c4.c

// c4.c - C in four functions

// char, int, and pointer types
// if, while, return, and expression statements
// just enough features to allow self-compilation and a bit more

// Written by Robert Swierczek

#include <stdio.h>
#include <stdlib.h>
#include <memory.h>
#include <unistd.h>
#include <fcntl.h>
#define int long long

char *p, *lp, // current position in source code
     *data;   // data/bss pointer

int *e, *le,  // current position in emitted code
    *id,      // currently parsed identifier
    *sym,     // symbol table (simple list of identifiers)
    tk,       // current token
    ival,     // current token value
    ty,       // current expression type
    loc,      // local variable offset
    line,     // current line number
    src,      // print source and assembly flag
    debug,    // print executed instructions
    ops,      // print opcodes
    portable; // generate portable code by making ptr, int and char the same size (1)

// tokens and classes (operators last and in precedence order)
enum {
  Num = 128, Fun, Sys, Glo, Loc, Id,
  Char, Else, Enum, If, Int, Return, Sizeof, While,
  Assign, Cond, Lor, Lan, Or, Xor, And, Eq, Ne, Lt, Gt, Le, Ge, Shl, Shr, Add, Sub, Mul, Div, Mod, Inc, Dec, Brak
};

// opcodes
enum { LEA ,IMM ,REF ,JMP ,JSR ,BZ  ,BNZ ,ENT ,ADJ ,LEV ,LI  ,LC  ,SI  ,SC  ,PSH ,
       OR  ,XOR ,AND ,EQ  ,NE  ,LT  ,GT  ,LE  ,GE  ,SHL ,SHR ,ADD ,SUB ,MUL ,DIV ,MOD ,
       OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT };

// types
enum { CHAR, INT, PTR };

// identifier offsets (since we can't create an ident struct)
enum { Tk, Hash, Name, Class, Type, Val, HClass, HType, HVal, Idsz };

void next()
{
  char *pp;

  while (tk = *p) {
    ++p;
    if (tk == '\n') {
      if (src) {
        printf("%d: %.*s", line, p - lp, lp);
        lp = p;
        while (le < e) {
          printf("%8.4s", &"LEA ,IMM ,REF ,JMP ,JSR ,BZ  ,BNZ ,ENT ,ADJ ,LEV ,LI  ,LC  ,SI  ,SC  ,PSH ,"
                           "OR  ,XOR ,AND ,EQ  ,NE  ,LT  ,GT  ,LE  ,GE  ,SHL ,SHR ,ADD ,SUB ,MUL ,DIV ,MOD ,"
                           "OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT,"[*++le * 5]);
          if (*le <= ADJ) printf(" %d\n", *++le); else printf("\n");
        }
      }
      ++line;
    }
    else if (tk == '#') {
      while (*p != 0 && *p != '\n') ++p;
    }
    else if ((tk >= 'a' && tk <= 'z') || (tk >= 'A' && tk <= 'Z') || tk == '_') {
      pp = p - 1;
      while ((*p >= 'a' && *p <= 'z') || (*p >= 'A' && *p <= 'Z') || (*p >= '0' && *p <= '9') || *p == '_')
        tk = tk * 47 + *p++;
      tk = (tk << 6) + (p - pp);
      id = sym;
      while (id[Tk]) {
        if (tk == id[Hash] && !memcmp((char *)id[Name], pp, p - pp)) { tk = id[Tk]; return; }
        id = id + Idsz;
      }
      id[Name] = (int)pp;
      id[Hash] = tk;
      tk = id[Tk] = Id;
      return;
    }
    else if (tk >= '0' && tk <= '9') {
      if (ival = tk - '0') { while (*p >= '0' && *p <= '9') ival = ival * 10 + *p++ - '0'; }
      else if (*p == 'x' || *p == 'X') {
        while ((tk = *++p) && ((tk >= '0' && tk <= '9') || (tk >= 'a' && tk <= 'f') || (tk >= 'A' && tk <= 'F')))
          ival = ival * 16 + (tk & 15) + (tk >= 'A' ? 9 : 0);
      }
      else { while (*p >= '0' && *p <= '7') ival = ival * 8 + *p++ - '0'; }
      tk = Num;
      return;
    }
    else if (tk == '/') {
      if (*p == '/') {
        ++p;
        while (*p != 0 && *p != '\n') ++p;
      }
      else {
        tk = Div;
        return;
      }
    }
    else if (tk == '\'' || tk == '"') {
      pp = data;
      while (*p != 0 && *p != tk) {
        if ((ival = *p++) == '\\') {
          if ((ival = *p++) == 'n') ival = '\n';
        }
        if (tk == '"') *data++ = ival;
      }
      ++p;
      if (tk == '"') ival = (int)pp; else tk = Num;
      return;
    }
    else if (tk == '=') { if (*p == '=') { ++p; tk = Eq; } else tk = Assign; return; }
    else if (tk == '+') { if (*p == '+') { ++p; tk = Inc; } else tk = Add; return; }
    else if (tk == '-') { if (*p == '-') { ++p; tk = Dec; } else tk = Sub; return; }
    else if (tk == '!') { if (*p == '=') { ++p; tk = Ne; } return; }
    else if (tk == '<') { if (*p == '=') { ++p; tk = Le; } else if (*p == '<') { ++p; tk = Shl; } else tk = Lt; return; }
    else if (tk == '>') { if (*p == '=') { ++p; tk = Ge; } else if (*p == '>') { ++p; tk = Shr; } else tk = Gt; return; }
    else if (tk == '|') { if (*p == '|') { ++p; tk = Lor; } else tk = Or; return; }
    else if (tk == '&') { if (*p == '&') { ++p; tk = Lan; } else tk = And; return; }
    else if (tk == '^') { tk = Xor; return; }
    else if (tk == '%') { tk = Mod; return; }
    else if (tk == '*') { tk = Mul; return; }
    else if (tk == '[') { tk = Brak; return; }
    else if (tk == '?') { tk = Cond; return; }
    else if (tk == '~' || tk == ';' || tk == '{' || tk == '}' || tk == '(' || tk == ')' || tk == ']' || tk == ',' || tk == ':') return;
  }
}

void expr(int lev)
{
  int t, *d;

  if (!tk) { printf("%d: unexpected eof in expression\n", line); exit(-1); }
  else if (tk == Num) { *++e = IMM; *++e = ival; next(); ty = INT; }
  else if (tk == '"') {
    *++e = REF; *++e = ival; next();
    while (tk == '"') next();
    data = (char *)((int)data + sizeof(int) & -sizeof(int)); ty = PTR; // Not sure if this needs to check portable here
  }
  else if (tk == Sizeof) {
    next(); if (tk == '(') next(); else { printf("%d: open paren expected in sizeof\n", line); exit(-1); }
    ty = INT; if (tk == Int) next(); else if (tk == Char) { next(); ty = CHAR; }
    while (tk == Mul) { next(); ty = ty + PTR; }
    if (tk == ')') next(); else { printf("%d: close paren expected in sizeof\n", line); exit(-1); }
    *++e = IMM; *++e = portable ? 1 : (ty == CHAR) ? sizeof(char) : sizeof(int);
    ty = INT;
  }
  else if (tk == Id) {
    d = id; next();
    if (tk == '(') {
      next();
      t = 0;
      while (tk != ')') { expr(Assign); *++e = PSH; ++t; if (tk == ',') next(); }
      next();
      if (d[Class] == Sys) *++e = d[Val];
      else if (d[Class] == Fun) { *++e = JSR; *++e = d[Val]; }
      else { printf("%d: bad function call\n", line); exit(-1); }
      if (t) { *++e = ADJ; *++e = t; }
      ty = d[Type];
    }
    else if (d[Class] == Num) { *++e = IMM; *++e = d[Val]; ty = INT; }
    else {
      if (d[Class] == Loc) { *++e = LEA; *++e = loc - d[Val]; }
      else if (d[Class] == Glo) { *++e = REF; *++e = d[Val]; } // TODO
      else { printf("%d: undefined variable\n", line); exit(-1); }
      *++e = ((ty = d[Type]) == CHAR) ? LC : LI;
    }
  }
  else if (tk == '(') {
    next();
    if (tk == Int || tk == Char) {
      t = (tk == Int) ? INT : CHAR; next();
      while (tk == Mul) { next(); t = t + PTR; }
      if (tk == ')') next(); else { printf("%d: bad cast\n", line); exit(-1); }
      expr(Inc);
      ty = t;
    }
    else {
      expr(Assign);
      if (tk == ')') next(); else { printf("%d: close paren expected\n", line); exit(-1); }
    }
  }
  else if (tk == Mul) {
    next(); expr(Inc);
    if (ty > INT) ty = ty - PTR; else { printf("%d: bad dereference\n", line); exit(-1); }
    *++e = (ty == CHAR) ? LC : LI;
  }
  else if (tk == And) {
    next(); expr(Inc);
    if (*e == LC || *e == LI) --e; else { printf("%d: bad address-of\n", line); exit(-1); }
    ty = ty + PTR;
  }
  else if (tk == '!') { next(); expr(Inc); *++e = PSH; *++e = IMM; *++e = 0; *++e = EQ; ty = INT; }
  else if (tk == '~') { next(); expr(Inc); *++e = PSH; *++e = IMM; *++e = -1; *++e = XOR; ty = INT; }
  else if (tk == Add) { next(); expr(Inc); ty = INT; }
  else if (tk == Sub) {
    next(); *++e = IMM;
    if (tk == Num) { *++e = -ival; next(); } else { *++e = -1; *++e = PSH; expr(Inc); *++e = MUL; }
    ty = INT;
  }
  else if (tk == Inc || tk == Dec) {
    t = tk; next(); expr(Inc);
    if (*e == LC) { *e = PSH; *++e = LC; }
    else if (*e == LI) { *e = PSH; *++e = LI; }
    else { printf("%d: bad lvalue in pre-increment\n", line); exit(-1); }
    *++e = PSH;
    *++e = IMM; *++e = portable ? 1 : (ty > PTR) ? sizeof(int) : sizeof(char);
    *++e = (t == Inc) ? ADD : SUB;
    *++e = (ty == CHAR) ? SC : SI;
  }
  else { printf("%d: bad expression\n", line); exit(-1); }

  while (tk >= lev) { // "precedence climbing" or "Top Down Operator Precedence" method
    t = ty;
    if (tk == Assign) {
      next();
      if (*e == LC || *e == LI) *e = PSH; else { printf("%d: bad lvalue in assignment\n", line); exit(-1); }
      expr(Assign); *++e = ((ty = t) == CHAR) ? SC : SI;
    }
    else if (tk == Cond) {
      next();
      *++e = BZ; d = ++e;
      expr(Assign);
      if (tk == ':') next(); else { printf("%d: conditional missing colon\n", line); exit(-1); }
      *d = (int)(e + 3); *++e = JMP; d = ++e;
      expr(Cond);
      *d = (int)(e + 1);
    }
    else if (tk == Lor) { next(); *++e = BNZ; d = ++e; expr(Lan); *d = (int)(e + 1); ty = INT; }
    else if (tk == Lan) { next(); *++e = BZ;  d = ++e; expr(Or);  *d = (int)(e + 1); ty = INT; }
    else if (tk == Or)  { next(); *++e = PSH; expr(Xor); *++e = OR;  ty = INT; }
    else if (tk == Xor) { next(); *++e = PSH; expr(And); *++e = XOR; ty = INT; }
    else if (tk == And) { next(); *++e = PSH; expr(Eq);  *++e = AND; ty = INT; }
    else if (tk == Eq)  { next(); *++e = PSH; expr(Lt);  *++e = EQ;  ty = INT; }
    else if (tk == Ne)  { next(); *++e = PSH; expr(Lt);  *++e = NE;  ty = INT; }
    else if (tk == Lt)  { next(); *++e = PSH; expr(Shl); *++e = LT;  ty = INT; }
    else if (tk == Gt)  { next(); *++e = PSH; expr(Shl); *++e = GT;  ty = INT; }
    else if (tk == Le)  { next(); *++e = PSH; expr(Shl); *++e = LE;  ty = INT; }
    else if (tk == Ge)  { next(); *++e = PSH; expr(Shl); *++e = GE;  ty = INT; }
    else if (tk == Shl) { next(); *++e = PSH; expr(Add); *++e = SHL; ty = INT; }
    else if (tk == Shr) { next(); *++e = PSH; expr(Add); *++e = SHR; ty = INT; }
    else if (tk == Add) {
      next(); *++e = PSH; expr(Mul);
      if ((ty = t) > PTR) { *++e = PSH; *++e = IMM; *++e = portable ? 1 : sizeof(int); *++e = MUL;  }
      *++e = ADD;
    }
    else if (tk == Sub) {
      next(); *++e = PSH; expr(Mul);
      if (t > PTR && t == ty) { *++e = SUB; *++e = PSH; *++e = IMM; *++e = portable ? 1 : sizeof(int); *++e = DIV; ty = INT; }
      else if ((ty = t) > PTR) { *++e = PSH; *++e = IMM; *++e = portable ? 1 : sizeof(int); *++e = MUL; *++e = SUB; }
      else *++e = SUB;
    }
    else if (tk == Mul) { next(); *++e = PSH; expr(Inc); *++e = MUL; ty = INT; }
    else if (tk == Div) { next(); *++e = PSH; expr(Inc); *++e = DIV; ty = INT; }
    else if (tk == Mod) { next(); *++e = PSH; expr(Inc); *++e = MOD; ty = INT; }
    else if (tk == Inc || tk == Dec) {
      if (*e == LC) { *e = PSH; *++e = LC; }
      else if (*e == LI) { *e = PSH; *++e = LI; }
      else { printf("%d: bad lvalue in post-increment\n", line); exit(-1); }
      *++e = PSH; *++e = IMM; *++e = portable ? 1 : (ty > PTR) ? sizeof(int) : sizeof(char);
      *++e = (tk == Inc) ? ADD : SUB;
      *++e = (ty == CHAR) ? SC : SI;
      *++e = PSH; *++e = IMM; *++e = portable ? 1 : (ty > PTR) ? sizeof(int) : sizeof(char);
      *++e = (tk == Inc) ? SUB : ADD;
      next();
    }
    else if (tk == Brak) {
      next(); *++e = PSH; expr(Assign);
      if (tk == ']') next(); else { printf("%d: close bracket expected\n", line); exit(-1); }
      if (t > PTR) { *++e = PSH; *++e = IMM; *++e = portable ? 1 : sizeof(int); *++e = MUL;  }
      else if (t < PTR) { printf("%d: pointer type expected\n", line); exit(-1); }
      *++e = ADD;
      *++e = ((ty = t - PTR) == CHAR) ? LC : LI;
    }
    else { printf("%d: compiler error tk=%d\n", line, tk); exit(-1); }
  }
}

void stmt()
{
  int *a, *b;

  if (tk == If) {
    next();
    if (tk == '(') next(); else { printf("%d: open paren expected\n", line); exit(-1); }
    expr(Assign);
    if (tk == ')') next(); else { printf("%d: close paren expected\n", line); exit(-1); }
    *++e = BZ; b = ++e;
    stmt();
    if (tk == Else) {
      *b = (int)(e + 3); *++e = JMP; b = ++e;
      next();
      stmt();
    }
    *b = (int)(e + 1);
  }
  else if (tk == While) {
    next();
    a = e + 1;
    if (tk == '(') next(); else { printf("%d: open paren expected\n", line); exit(-1); }
    expr(Assign);
    if (tk == ')') next(); else { printf("%d: close paren expected\n", line); exit(-1); }
    *++e = BZ; b = ++e;
    stmt();
    *++e = JMP; *++e = (int)a;
    *b = (int)(e + 1);
  }
  else if (tk == Return) {
    next();
    if (tk != ';') expr(Assign);
    *++e = LEV;
    if (tk == ';') next(); else { printf("%d: semicolon expected\n", line); exit(-1); }
  }
  else if (tk == '{') {
    next();
    while (tk != '}') stmt();
    next();
  }
  else if (tk == ';') {
    next();
  }
  else {
    expr(Assign);
    if (tk == ';') next(); else { printf("%d: semicolon expected\n", line); exit(-1); }
  }
}

int main(signed argc, char **argv)
{
  int fd, bt, ty, poolsz, *idmain;
  int *pc, *sp, *bp, a, cycle; // vm registers
  int i, *t, *spstart, *stack_ix; // temps

  int *estart;  // start of emitted code
  char *datastart, *datastart2; // start of data/bss

  --argc; ++argv;
  if (argc > 0 && **argv == '-' && (*argv)[1] == 's') { src = 1; --argc; ++argv; }
  if (argc > 0 && **argv == '-' && (*argv)[1] == 'd') { debug = 1; --argc; ++argv; }
  if (argc > 0 && **argv == '-' && (*argv)[1] == 'b') { ops = 1; --argc; ++argv; }
  if (argc > 0 && **argv == '-' && (*argv)[1] == 'p') { portable = 1; --argc; ++argv; }
  if (argc < 1) { printf("usage: c4 [-s] [-d] file ...\n"); return -1; }

  if ((fd = open(*argv, 0)) < 0) { printf("could not open(%s)\n", *argv); return -1; }

  poolsz = 256*1024; // arbitrary size
  if (!(sym = malloc(poolsz))) { printf("could not malloc(%d) symbol area\n", poolsz); return -1; }
  if (!(estart = le = e = malloc(poolsz))) { printf("could not malloc(%d) text area\n", poolsz); return -1; }
  if (!(datastart = data = malloc(poolsz))) { printf("could not malloc(%d) data area\n", poolsz); return -1; }
  if (!(sp = malloc(poolsz))) { printf("could not malloc(%d) stack area\n", poolsz); return -1; }

  memset(sym,  0, poolsz);
  memset(e,    0, poolsz);
  memset(data, 0, poolsz);

  p = "char else enum if int return sizeof while "
      "open read close printf malloc free memset memcmp exit void main";
  i = Char; while (i <= While) { next(); id[Tk] = i++; } // add keywords to symbol table
  i = OPEN; while (i <= EXIT) { next(); id[Class] = Sys; id[Type] = INT; id[Val] = i++; } // add library to symbol table
  next(); id[Tk] = Char; // handle void type
  next(); idmain = id; // keep track of main

  if (!(lp = p = malloc(poolsz))) { printf("could not malloc(%d) source area\n", poolsz); return -1; }
  if ((i = read(fd, p, poolsz-1)) <= 0) { printf("read() returned %d\n", i); return -1; }
  p[i] = 0;
  close(fd);

  // parse declarations
  line = 1;
  next();
  while (tk) {
    bt = INT; // basetype
    if (tk == Int) next();
    else if (tk == Char) { next(); bt = CHAR; }
    else if (tk == Enum) {
      next();
      if (tk != '{') next();
      if (tk == '{') {
        next();
        i = 0;
        while (tk != '}') {
          if (tk != Id) { printf("%d: bad enum identifier %d\n", line, tk); return -1; }
          next();
          if (tk == Assign) {
            next();
            if (tk != Num) { printf("%d: bad enum initializer\n", line); return -1; }
            i = ival;
            next();
          }
          id[Class] = Num; id[Type] = INT; id[Val] = i++;
          if (tk == ',') next();
        }
        next();
      }
    }
    while (tk != ';' && tk != '}') {
      ty = bt;
      while (tk == Mul) { next(); ty = ty + PTR; }
      if (tk != Id) { printf("%d: bad global declaration\n", line); return -1; }
      if (id[Class]) { printf("%d: duplicate global definition\n", line); return -1; }
      next();
      id[Type] = ty;
      if (tk == '(') { // function
        id[Class] = Fun;
        id[Val] = (int)(e + 1);
        next(); i = 0;
        while (tk != ')') {
          ty = INT;
          if (tk == Int) next();
          else if (tk == Char) { next(); ty = CHAR; }
          while (tk == Mul) { next(); ty = ty + PTR; }
          if (tk != Id) { printf("%d: bad parameter declaration\n", line); return -1; }
          if (id[Class] == Loc) { printf("%d: duplicate parameter definition\n", line); return -1; }
          id[HClass] = id[Class]; id[Class] = Loc;
          id[HType]  = id[Type];  id[Type] = ty;
          id[HVal]   = id[Val];   id[Val] = i++;
          next();
          if (tk == ',') next();
        }
        next();
        if (tk != '{') { printf("%d: bad function definition\n", line); return -1; }
        loc = ++i;
        next();
        while (tk == Int || tk == Char) {
          bt = (tk == Int) ? INT : CHAR;
          next();
          while (tk != ';') {
            ty = bt;
            while (tk == Mul) { next(); ty = ty + PTR; }
            if (tk != Id) { printf("%d: bad local declaration\n", line); return -1; }
            if (id[Class] == Loc) { printf("%d: duplicate local definition\n", line); return -1; }
            id[HClass] = id[Class]; id[Class] = Loc;
            id[HType]  = id[Type];  id[Type] = ty;
            id[HVal]   = id[Val];   id[Val] = ++i;
            next();
            if (tk == ',') next();
          }
          next();
        }
        *++e = ENT; *++e = i - loc;
        while (tk != '}') stmt();
        *++e = LEV;
        id = sym; // unwind symbol table locals
        while (id[Tk]) {
          if (id[Class] == Loc) {
            id[Class] = id[HClass];
            id[Type] = id[HType];
            id[Val] = id[HVal];
          }
          id = id + Idsz;
        }
      }
      else {
        id[Class] = Glo;
        id[Val] = (int)data;
        data = data + sizeof(int);
      }
      if (tk == ',') next();
    }
    next();
  }

  if (!(pc = (int *)idmain[Val])) { printf("main() not defined\n"); return -1; }
  if (src) return 0;

  // setup stack
  bp = sp = (int *)((int)sp + poolsz);
  spstart = sp;
  *--sp = EXIT; // call exit if main returns
  *--sp = PSH; t = sp;
  *--sp = argc;
  *--sp = (int)argv;
  *--sp = (int)t;

  // Dump the heap and op codes
  // The format is:
  //  <data size>
  //  <data>
  //  <main address>
  //  <opcodes> \n <opcodes> \n ...
  if (ops) {
    estart++; // Instructions start being encoded at position 1. See line containing: *++e = ENT; *++e = i - loc;
    // <data size>
    printf("%d\n", data - datastart);
    // <data>
    datastart2 = datastart; // Saving this to compute reference offset
    while (datastart < data) {
      // Escape non-printable characters and '\'
      if (*datastart <= 31 || *datastart >= 127 || *datastart == '\\') {
        printf("\\%x%x", *datastart / 16, *datastart % 16);
      } else {
        printf("%c", *datastart);
      }
      datastart++;
    }
    datastart = datastart2;
    printf("\n");

    // <main address>
    printf("%d\n", (pc - (int *)estart));
    // <opcodes>
    le = estart;
    while (le <= e) {
      i = *le;
      // Relocate addresses
      if (i == JMP || i == JSR || i == BZ || i == BNZ) {
        printf("%4.4s", &"LEA ,IMM ,REF ,JMP ,JSR ,BZ  ,BNZ ,ENT ,ADJ ,LEV ,LI  ,LC  ,SI  ,SC  ,PSH ,"
                              "OR  ,XOR ,AND ,EQ  ,NE  ,LT  ,GT  ,LE  ,GE  ,SHL ,SHR ,ADD ,SUB ,MUL ,DIV ,MOD ,"
                              "OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT,"[i * 5]);
        if (*le <= ADJ) printf(" %d\n", ((*++le) - (int) estart) / sizeof(int)); else printf("\n");
      } else if (i == REF) {
        printf("REF  %d\n", (*++le - (int) datastart));
      } else {
        printf("%4.4s", &"LEA ,IMM ,REF ,JMP ,JSR ,BZ  ,BNZ ,ENT ,ADJ ,LEV ,LI  ,LC  ,SI  ,SC  ,PSH ,"
                              "OR  ,XOR ,AND ,EQ  ,NE  ,LT  ,GT  ,LE  ,GE  ,SHL ,SHR ,ADD ,SUB ,MUL ,DIV ,MOD ,"
                              "OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT,"[i * 5]);
        if (*le <= ADJ) printf(" %d\n", *++le); else printf("\n");
      }
      le++;
    }
    return 0;
  }

  // run...
  cycle = 0;
  while (1) {
    i = *pc++; ++cycle;
    if (debug) {
      printf("%d> %.4s", cycle,
        &"LEA ,IMM ,REF ,JMP ,JSR ,BZ  ,BNZ ,ENT ,ADJ ,LEV ,LI  ,LC  ,SI  ,SC  ,PSH ,"
         "OR  ,XOR ,AND ,EQ  ,NE  ,LT  ,GT  ,LE  ,GE  ,SHL ,SHR ,ADD ,SUB ,MUL ,DIV ,MOD ,"
         "OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT,"[i * 5]);
      if (i <= ADJ) printf(" %d\n", *pc); else printf("\n");

      printf("    pc = %d, sp = %d, bp = %d, a = %d\n", pc, sp, bp, a);

      // Print stack
      stack_ix = spstart;
      while (stack_ix > sp) {
        stack_ix--;
        printf("    _stack_%d = %d\n", stack_ix, *stack_ix);
      }
    }
    if      (i == LEA) a = (int)(bp + *pc++);                             // load local address
    else if (i == IMM) a = *pc++;                                         // load global address or immediate
    else if (i == REF) a = *pc++;                                         // load global address
    else if (i == JMP) pc = (int *)*pc;                                   // jump
    else if (i == JSR) { *--sp = (int)(pc + 1); pc = (int *)*pc; }        // jump to subroutine
    else if (i == BZ)  pc = a ? pc + 1 : (int *)*pc;                      // branch if zero
    else if (i == BNZ) pc = a ? (int *)*pc : pc + 1;                      // branch if not zero
    else if (i == ENT) { *--sp = (int)bp; bp = sp; sp = sp - *pc++; }     // enter subroutine
    else if (i == ADJ) sp = sp + *pc++;                                   // stack adjust
    else if (i == LEV) { sp = bp; bp = (int *)*sp++; pc = (int *)*sp++; } // leave subroutine
    else if (i == LI)  a = *(int *)a;                                     // load int
    else if (i == LC)  a = *(char *)a;                                    // load char
    else if (i == SI)  *(int *)*sp++ = a;                                 // store int
    else if (i == SC)  a = *(char *)*sp++ = a;                            // store char
    else if (i == PSH) *--sp = a;                                         // push

    else if (i == OR)  a = *sp++ |  a;
    else if (i == XOR) a = *sp++ ^  a;
    else if (i == AND) a = *sp++ &  a;
    else if (i == EQ)  a = *sp++ == a;
    else if (i == NE)  a = *sp++ != a;
    else if (i == LT)  a = *sp++ <  a;
    else if (i == GT)  a = *sp++ >  a;
    else if (i == LE)  a = *sp++ <= a;
    else if (i == GE)  a = *sp++ >= a;
    else if (i == SHL) a = *sp++ << a;
    else if (i == SHR) a = *sp++ >> a;
    else if (i == ADD) a = *sp++ +  a;
    else if (i == SUB) a = *sp++ -  a;
    else if (i == MUL) a = *sp++ *  a;
    else if (i == DIV) a = *sp++ /  a;
    else if (i == MOD) a = *sp++ %  a;

    else if (i == OPEN) a = open((char *)sp[1], *sp);
    else if (i == READ) a = read(sp[2], (char *)sp[1], *sp);
    else if (i == CLOS) a = close(*sp);
    else if (i == PRTF) { t = sp + pc[1]; a = printf((char *)t[-1], t[-2], t[-3], t[-4], t[-5], t[-6]); }
    else if (i == MALC) a = (int)malloc(*sp);
    else if (i == FREE) free((void *)*sp);
    else if (i == MSET) a = (int)memset((char *)sp[2], sp[1], *sp);
    else if (i == MCMP) a = memcmp((char *)sp[2], (char *)sp[1], *sp);
    else if (i == EXIT) { printf("exit(%d) cycle = %d\n", *sp, cycle); return *sp; }
    else { printf("unknown instruction = %d! cycle = %d\n", i, cycle); return -1; }
  }
}