Merge pull request #32 from nubok/patch-2

Avoid undefined behavior - bp is initialized when setting up the stack
2017-08-21 17:39:47 -04:00 · 2017-08-21 23:30:09 +02:00 · 2017-02-24 06:21:56 -05:00 · 2017-02-24 17:28:35 +08:00 · 2016-02-26 01:17:04 -05:00 · 2016-02-25 20:59:44 -05:00
2 changed files with 146 additions and 196 deletions
--- a/README.md
+++ b/README.md
@ -1,7 +1,7 @@
 c4 - C in four functions
 ========================

-An exercise in minimalism.  **This branch adds switch statement support.**
+An exercise in minimalism.

 Try the following:

--- a/c4.c
+++ b/c4.c
@ -1,15 +1,15 @@
 // c4.c - C in four functions

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

 // Written by Robert Swierczek

-#include <unistd.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <memory.h>
+#include <unistd.h>
 #include <fcntl.h>

 char *p, *lp, // current position in source code
@ -18,9 +18,6 @@ char *p, *lp, // current position in source code
 int *e, *le,  // current position in emitted code
    *id,      // currently parsed identifier
    *sym,     // symbol table (simple list of identifiers)
-    *cas,     // case statement patch-up pointer
-    *brk,     // break statement patch-up pointer
-    *def,     // default statement patch-up pointer
    tk,       // current token
    ival,     // current token value
    ty,       // current expression type
@ -32,14 +29,14 @@ int *e, *le,  // current position in emitted code
 // tokens and classes (operators last and in precedence order)
 enum {
  Num = 128, Fun, Sys, Glo, Loc, Id,
-  Break, Case, Char, Default, Else, Enum, If, Int, Return, Sizeof, Switch, While,
+  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 ,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,MSET,MCMP,EXIT };
+       OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT };

 // types
 enum { CHAR, INT, PTR };
@ -53,7 +50,23 @@ void next()

  while (tk = *p) {
    ++p;
-    if ((tk >= 'a' && tk <= 'z') || (tk >= 'A' && tk <= 'Z') || tk == '_') {
+    if (tk == '\n') {
+      if (src) {
+        printf("%d: %.*s", line, p - lp, lp);
+        lp = p;
+        while (le < e) {
+          printf("%8.4s", &"LEA ,IMM ,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 * 147 + *p++;
@ -78,25 +91,7 @@ void next()
      tk = Num;
      return;
    }
-    switch (tk) {
-    case '\n':
-      if (src) {
-        printf("%d: %.*s", line, p - lp, lp);
-        lp = p;
-        while (le < e) {
-          printf("%8.4s", &"LEA ,IMM ,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,MSET,MCMP,EXIT,"[*++le * 5]);
-          if (*le <= ADJ) printf(" %d\n", *++le); else printf("\n");
-        }
-      }
-      ++line;
-    case ' ': case '\t': case '\v': case '\f': case '\r':
-      break;
-    case '#':
-      while (*p != 0 && *p != '\n') ++p;
-      break;
-    case '/':
+    else if (tk == '/') {
      if (*p == '/') {
        ++p;
        while (*p != 0 && *p != '\n') ++p;
@ -105,40 +100,33 @@ void next()
        tk = Div;
        return;
      }
-      break;
-    case '\'':
-    case '"':
+    }
+    else if (tk == '\'' || tk == '"') {
      pp = data;
      while (*p != 0 && *p != tk) {
        if ((ival = *p++) == '\\') {
-          switch (ival = *p++) {
-          case 'n': ival = '\n'; break;
-          case 't': ival = '\t'; break;
-          case 'v': ival = '\v'; break;
-          case 'f': ival = '\f'; break;
-          case 'r': ival = '\r';
-          }
+          if ((ival = *p++) == 'n') ival = '\n';
        }
        if (tk == '"') *data++ = ival;
      }
      ++p;
      if (tk == '"') ival = (int)pp; else tk = Num;
      return;
-    case '=': if (*p == '=') { ++p; tk = Eq; } else tk = Assign; return;
-    case '+': if (*p == '+') { ++p; tk = Inc; } else tk = Add; return;
-    case '-': if (*p == '-') { ++p; tk = Dec; } else tk = Sub; return;
-    case '!': if (*p == '=') { ++p; tk = Ne; } return;
-    case '<': if (*p == '=') { ++p; tk = Le; } else if (*p == '<') { ++p; tk = Shl; } else tk = Lt; return;
-    case '>': if (*p == '=') { ++p; tk = Ge; } else if (*p == '>') { ++p; tk = Shr; } else tk = Gt; return;
-    case '|': if (*p == '|') { ++p; tk = Lor; } else tk = Or; return;
-    case '&': if (*p == '&') { ++p; tk = Lan; } else tk = And; return;
-    case '^': tk = Xor; return;
-    case '%': tk = Mod; return;
-    case '*': tk = Mul; return;
-    case '[': tk = Brak; return;
-    case '?': tk = Cond; return;
-    default: 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;
  }
 }

@ -146,23 +134,22 @@ void expr(int lev)
 {
  int t, *d;

-  switch (tk) {
-  case 0: printf("%d: unexpected eof in expression\n", line); exit(-1);
-  case Num: *++e = IMM; *++e = ival; next(); ty = INT; break;
-  case '"':
+  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 = IMM; *++e = ival; next();
    while (tk == '"') next();
    data = (char *)((int)data + sizeof(int) & -sizeof(int)); ty = PTR;
-    break;
-  case Sizeof:
+  }
+  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 = (ty == CHAR) ? sizeof(char) : sizeof(int);
    ty = INT;
-    break;
-  case Id:
+  }
+  else if (tk == Id) {
    d = id; next();
    if (tk == '(') {
      next();
@ -182,8 +169,8 @@ void expr(int lev)
      else { printf("%d: undefined variable\n", line); exit(-1); }
      *++e = ((ty = d[Type]) == CHAR) ? LC : LI;
    }
-    break;
-  case '(':
+  }
+  else if (tk == '(') {
    next();
    if (tk == Int || tk == Char) {
      t = (tk == Int) ? INT : CHAR; next();
@ -196,26 +183,26 @@ void expr(int lev)
      expr(Assign);
      if (tk == ')') next(); else { printf("%d: close paren expected\n", line); exit(-1); }
    }
-    break;
-  case Mul:
+  }
+  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;
-    break;
-  case And:
+  }
+  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;
-    break;
-  case '!': next(); expr(Inc); *++e = PSH; *++e = IMM; *++e = 0; *++e = EQ; ty = INT; break;
-  case '~': next(); expr(Inc); *++e = PSH; *++e = IMM; *++e = -1; *++e = XOR; ty = INT; break;
-  case Add: next(); expr(Inc); ty = INT; break;
-  case Sub:
+  }
+  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;
-    break;
-  case Inc: case Dec:
+  }
+  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; }
@ -224,19 +211,17 @@ void expr(int lev)
    *++e = IMM; *++e = (ty > PTR) ? sizeof(int) : sizeof(char);
    *++e = (t == Inc) ? ADD : SUB;
    *++e = (ty == CHAR) ? SC : SI;
-    break;
-  default: printf("%d: bad expression\n", line); exit(-1);
  }
+  else { printf("%d: bad expression\n", line); exit(-1); }

  while (tk >= lev) { // "precedence climbing" or "Top Down Operator Precedence" method
    t = ty;
-    switch (tk) {
-    case Assign:
+    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;
-      break;
-    case Cond:
+    }
+    else if (tk == Cond) {
      next();
      *++e = BZ; d = ++e;
      expr(Assign);
@ -244,35 +229,35 @@ void expr(int lev)
      *d = (int)(e + 3); *++e = JMP; d = ++e;
      expr(Cond);
      *d = (int)(e + 1);
-      break;
-    case Lor: next(); *++e = BNZ; d = ++e; expr(Lan); *d = (int)(e + 1); ty = INT; break;
-    case Lan: next(); *++e = BZ;  d = ++e; expr(Or);  *d = (int)(e + 1); ty = INT; break;
-    case Or:  next(); *++e = PSH; expr(Xor); *++e = OR;  ty = INT; break;
-    case Xor: next(); *++e = PSH; expr(And); *++e = XOR; ty = INT; break;
-    case And: next(); *++e = PSH; expr(Eq);  *++e = AND; ty = INT; break;
-    case Eq:  next(); *++e = PSH; expr(Lt);  *++e = EQ;  ty = INT; break;
-    case Ne:  next(); *++e = PSH; expr(Lt);  *++e = NE;  ty = INT; break;
-    case Lt:  next(); *++e = PSH; expr(Shl); *++e = LT;  ty = INT; break;
-    case Gt:  next(); *++e = PSH; expr(Shl); *++e = GT;  ty = INT; break;
-    case Le:  next(); *++e = PSH; expr(Shl); *++e = LE;  ty = INT; break;
-    case Ge:  next(); *++e = PSH; expr(Shl); *++e = GE;  ty = INT; break;
-    case Shl: next(); *++e = PSH; expr(Add); *++e = SHL; ty = INT; break;
-    case Shr: next(); *++e = PSH; expr(Add); *++e = SHR; ty = INT; break;
-    case Add:
+    }
+    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 = sizeof(int); *++e = MUL;  }
      *++e = ADD;
-      break;
-    case Sub:
+    }
+    else if (tk == Sub) {
      next(); *++e = PSH; expr(Mul);
      if (t > PTR && t == ty) { *++e = SUB; *++e = PSH; *++e = IMM; *++e = sizeof(int); *++e = DIV; ty = INT; }
      else if ((ty = t) > PTR) { *++e = PSH; *++e = IMM; *++e = sizeof(int); *++e = MUL; *++e = SUB; }
      else *++e = SUB;
-      break;
-    case Mul: next(); *++e = PSH; expr(Inc); *++e = MUL; ty = INT; break;
-    case Div: next(); *++e = PSH; expr(Inc); *++e = DIV; ty = INT; break;
-    case Mod: next(); *++e = PSH; expr(Inc); *++e = MOD; ty = INT; break;
-    case Inc: case Dec:
+    }
+    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); }
@ -282,26 +267,24 @@ void expr(int lev)
      *++e = PSH; *++e = IMM; *++e = (ty > PTR) ? sizeof(int) : sizeof(char);
      *++e = (tk == Inc) ? SUB : ADD;
      next();
-      break;
-    case Brak:
+    }
+    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 = 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;
-      break;
-    default: printf("%d: compiler error tk=%d\n", line, tk); exit(-1);
    }
+    else { printf("%d: compiler error tk=%d\n", line, tk); exit(-1); }
  }
 }

 void stmt()
 {
-  int *a, *b, *d, i;
+  int *a, *b;

-  switch (tk) {
-  case If:
+  if (tk == If) {
    next();
    if (tk == '(') next(); else { printf("%d: open paren expected\n", line); exit(-1); }
    expr(Assign);
@ -314,8 +297,8 @@ void stmt()
      stmt();
    }
    *b = (int)(e + 1);
-    return;
-  case While:
+  }
+  else if (tk == While) {
    next();
    a = e + 1;
    if (tk == '(') next(); else { printf("%d: open paren expected\n", line); exit(-1); }
@ -325,54 +308,22 @@ void stmt()
    stmt();
    *++e = JMP; *++e = (int)a;
    *b = (int)(e + 1);
-    return;
-  case Switch:
-    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); }
-    a = cas; *++e = JMP; cas = ++e;
-    b = brk; d = def; brk = def = 0;
-    stmt();
-    *cas = def ? (int)def : (int)(e + 1); cas = a; 
-    while (brk) { a = (int *)*brk; *brk = (int)(e + 1); brk = a; }
-    brk = b; def = d;
-    return;
-  case Case:
-    *++e = JMP; ++e; *e = (int)(e + 7); *++e = PSH; i = *cas; *cas = (int)e; 
-    next();
-    expr(Or);
-    if (e[-1] != IMM) { printf("%d: bad case immediate\n", line); exit(-1); }
-    *e = *e - i; *++e = SUB; *++e = BNZ; cas = ++e; *e = i + e[-3];
-    if (tk == ':') next(); else { printf("%d: colon expected\n", line); exit(-1); }
-    stmt();
-    return;
-  case Break:
-    next();
-    if (tk == ';') next(); else { printf("%d: semicolon expected\n", line); exit(-1); }
-    *++e = JMP; *++e = (int)brk; brk = e;
-    return;
-  case Default:
-    next();
-    if (tk == ':') next(); else { printf("%d: colon expected\n", line); exit(-1); }
-    def = e + 1;
-    stmt();
-    return;
-  case Return:
+  }
+  else if (tk == Return) {
    next();
    if (tk != ';') expr(Assign);
    *++e = LEV;
    if (tk == ';') next(); else { printf("%d: semicolon expected\n", line); exit(-1); }
-    return;
-  case '{':
+  }
+  else if (tk == '{') {
    next();
    while (tk != '}') stmt();
    next();
-    return;
-  case ';':
+  }
+  else if (tk == ';') {
    next();
-    return;
-  default:
+  }
+  else {
    expr(Assign);
    if (tk == ';') next(); else { printf("%d: semicolon expected\n", line); exit(-1); }
  }
@ -401,9 +352,9 @@ int main(int argc, char **argv)
  memset(e,    0, poolsz);
  memset(data, 0, poolsz);

-  p = "break case char default else enum if int return sizeof switch while "
-      "open read close printf malloc memset memcmp exit void main";
-  i = Break; while (i <= While) { next(); id[Tk] = i++; } // add keywords to symbol table
+  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
@ -512,7 +463,7 @@ int main(int argc, char **argv)
  if (src) return 0;

  // setup stack
-  sp = (int *)((int)sp + poolsz);
+  bp = sp = (int *)((int)sp + poolsz);
  *--sp = EXIT; // call exit if main returns
  *--sp = PSH; t = sp;
  *--sp = argc;
@ -527,51 +478,50 @@ int main(int argc, char **argv)
      printf("%d> %.4s", cycle,
        &"LEA ,IMM ,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,MSET,MCMP,EXIT,"[i * 5]);
+         "OPEN,READ,CLOS,PRTF,MALC,FREE,MSET,MCMP,EXIT,"[i * 5]);
      if (i <= ADJ) printf(" %d\n", *pc); else printf("\n");
    }
-    switch (i) {
-    case LEA: a = (int)(bp + *pc++); break;                         // load local address
-    case IMM: a = *pc++; break;                                     // load global address or immediate
-    case JMP: pc = (int *)*pc; break;                               // jump
-    case JSR: *--sp = (int)(pc + 1); pc = (int *)*pc; break;        // jump to subroutine
-    case BZ:  pc = a ? pc + 1 : (int *)*pc; break;                  // branch if zero
-    case BNZ: pc = a ? (int *)*pc : pc + 1; break;                  // branch if not zero
-    case ENT: *--sp = (int)bp; bp = sp; sp = sp - *pc++; break;     // enter subroutine
-    case ADJ: sp = sp + *pc++; break;                               // stack adjust
-    case LEV: sp = bp; bp = (int *)*sp++; pc = (int *)*sp++; break; // leave subroutine
-    case LI:  a = *(int *)a; break;                                 // load int
-    case LC:  a = *(char *)a; break;                                // load char
-    case SI:  *(int *)*sp++ = a; break;                             // store int
-    case SC:  a = *(char *)*sp++ = a; break;                        // store char
-    case PSH: *--sp = a; break;                                     // push
+    if      (i == LEA) a = (int)(bp + *pc++);                             // load local address
+    else if (i == IMM) a = *pc++;                                         // load global address or immediate
+    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

-    case OR:  a = *sp++ |  a; break;
-    case XOR: a = *sp++ ^  a; break;
-    case AND: a = *sp++ &  a; break;
-    case EQ:  a = *sp++ == a; break;
-    case NE:  a = *sp++ != a; break;
-    case LT:  a = *sp++ <  a; break;
-    case GT:  a = *sp++ >  a; break;
-    case LE:  a = *sp++ <= a; break;
-    case GE:  a = *sp++ >= a; break;
-    case SHL: a = *sp++ << a; break;
-    case SHR: a = *sp++ >> a; break;
-    case ADD: a = *sp++ +  a; break;
-    case SUB: a = *sp++ -  a; break;
-    case MUL: a = *sp++ *  a; break;
-    case DIV: a = *sp++ /  a; break;
-    case MOD: a = *sp++ %  a; break;
+    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;

-    case OPEN: a = open((char *)sp[1], *sp); break;
-    case READ: a = read(sp[2], (char *)sp[1], *sp); break;
-    case CLOS: a = close(*sp); break;
-    case PRTF: t = sp + pc[1]; a = printf((char *)t[-1], t[-2], t[-3], t[-4], t[-5], t[-6]); break;
-    case MALC: a = (int)malloc(*sp); break;
-    case MSET: a = (int)memset((char *)sp[2], sp[1], *sp); break;
-    case MCMP: a = memcmp((char *)sp[2], (char *)sp[1], *sp); break;
-    case EXIT: printf("exit(%d) cycle = %d\n", *sp, cycle); return *sp;
-    default: printf("unknown instruction = %d! cycle = %d\n", i, cycle); return -1;
-    }
+    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; }
  }
 }
Author	SHA1	Message	Date
Robert Swierczek	3f098f3ea8	Merge pull request #32 from nubok/patch-2 Avoid undefined behavior - bp is initialized when setting up the stack	2017-08-21 17:39:47 -04:00
Wolfgang Keller	6884cb4de9	Avoid undefined behavior - bp is initialized when setting up the stack	2017-08-21 23:30:09 +02:00
Robert Swierczek	567db57ef2	Merge pull request #27 from chainhelen/master add a FREE opcode	2017-02-24 06:21:56 -05:00
chainhelen	461f117cda	add a FREE opcode	2017-02-24 17:28:35 +08:00
rswier	80db11debf	Revert "Added structures" This reverts commit `32b33ff4f6`.	2016-02-26 01:17:04 -05:00
rswier	32b33ff4f6	Added structures This change adds structures (struct) along with the dot (.) and arrow (->) operators. It is very silly to add this level of complexity while keeping it just four functions. But it had to be done :-)	2016-02-25 20:59:44 -05:00
rswier	e78a343e1d	Merge pull request #22 from neosilky/fix-compile Fix a compile error from missing include	2016-01-28 19:52:59 -05:00
Daniel Lockyer	021abbc0b4	Fix a compile error from missing include open() needs the <fcntl.h> include so this has been added.	2016-01-29 00:28:40 +00:00