better error messages

ldebug.c

@@ -1,5 +1,5 @@
 /*
-** $Id: ldebug.c,v 1.23 2000/06/12 13:52:05 roberto Exp roberto $
+** $Id: ldebug.c,v 1.24 2000/06/26 19:28:31 roberto Exp roberto $
 ** Debug Interface
 ** See Copyright Notice in lua.h
 */
@@ -13,10 +13,12 @@
 
 #include "lapi.h"
 #include "lauxlib.h"
+#include "lcode.h"
 #include "ldebug.h"
 #include "ldo.h"
 #include "lfunc.h"
 #include "lobject.h"
+#include "lopcodes.h"
 #include "lstate.h"
 #include "ltable.h"
 #include "ltm.h"
@@ -97,6 +99,13 @@ static int lua_nups (StkId f) {
 }
 
 
+static int lua_currentpc (StkId f) {
+  CallInfo *ci = infovalue(f);
+  LUA_ASSERT(L, ttype(f) == TAG_LMARK, "function has no pc");
+  return (*ci->pc - 1) - ci->func->f.l->code;
+}
+
+
 static int lua_currentline (StkId f) {
   if (ttype(f) != TAG_LMARK)
     return -1;  /* only active lua functions have current-line information */
@@ -104,15 +113,11 @@ static int lua_currentline (StkId f) {
     CallInfo *ci = infovalue(f);
     int *lines = ci->func->f.l->lines;
     if (!lines) return -1;  /* no static debug information */
-    else return lines[ci->pc];
+    else return lines[lua_currentpc(f)];
   }
 }
 
 
-static int lua_currentpc (StkId f) {
-  return infovalue(f)->pc;
-}
-
 
 static Proto *getluaproto (StkId f) {
   return (ttype(f) == TAG_LMARK) ?  infovalue(f)->func->f.l : NULL;
@@ -225,17 +230,136 @@ int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar) {
 }
 
 
+/*
+** {======================================================
+** Symbolic Execution
+** =======================================================
+*/
 
-static void call_index_error (lua_State *L, TObject *o, const char *v) {
-  luaL_verror(L, "attempt to %.10s a %.10s value", v, lua_type(L, o));
+static Instruction luaG_symbexec (const Proto *pt, int lastpc, int stackpos) {
+  int stack[MAXSTACK];  /* stores last instruction that changes each value */
+  const Instruction *code = pt->code;
+  int top = pt->numparams;
+  int pc = 0;
+  if (pt->is_vararg)  /* varargs? */
+    top++;  /* `arg' */
+  while (pc < lastpc) {
+    const Instruction i = code[pc++];
+    switch (GET_OPCODE(i)) {
+      case OP_CALL: {
+        int nresults = GETARG_B(i);
+        if (nresults == MULT_RET) nresults = 1;
+        top = GETARG_A(i);
+        while (nresults--)
+          stack[top++] = pc-1;
+        break;
+      }
+      case OP_PUSHNIL: {
+        int n;
+        for (n=0; n<GETARG_U(i); n++)
+          stack[top++] = pc-1;
+        break;
+      }
+      case OP_POP: {
+        top -= GETARG_U(i);
+        break;
+      }
+      case OP_SETTABLE:
+      case OP_SETLIST: {
+        top -= GETARG_B(i);
+        break;
+      }
+      case OP_SETMAP: {
+        top -= 2*GETARG_U(i);
+        break;
+      }
+      case OP_CONCAT: {
+        top -= GETARG_U(i);
+        stack[top++] = pc-1;
+        break;
+      }
+      case OP_JMPONT:
+      case OP_JMPONF: {
+        int newpc = pc + GETARG_S(i);
+        if (newpc >= lastpc) {
+          stack[top-1] = pc-1;  /* value generated by or-and */
+          pc = newpc;  /* do the jump */
+        }
+        else
+          top--;  /* original code did not jump; condition was false */
+        break;
+      }
+      case OP_PUSHNILJMP: {
+        break;  /* do not `push', to compensate next instruction */
+      }
+      case OP_CLOSURE: {
+        top -= GETARG_B(i);
+        stack[top++] = pc-1;
+        break;
+      }
+      default: {
+        int n;
+        LUA_ASSERT(NULL, luaK_opproperties[GET_OPCODE(i)].push != VD,
+                   "invalid opcode for default");
+        top -= luaK_opproperties[GET_OPCODE(i)].pop;
+        for (n=0; n<luaK_opproperties[GET_OPCODE(i)].push; n++)
+          stack[top++] = pc-1;
+      }
+    }
+  }
+  return code[stack[stackpos]];
 }
 
 
-void luaG_callerror (lua_State *L, TObject *func) {
-  call_index_error(L, func, "call");
+static const char *getname (lua_State *L, StkId obj, const char **name) {
+  StkId func = aux_stackedfunction(L, 0, obj);
+  if (func == NULL || ttype(func) != TAG_LMARK)
+    return NULL;  /* not a Lua function */
+  else {
+    Proto *p = infovalue(func)->func->f.l;
+    int pc = lua_currentpc(func);
+    int stackpos = obj - (func+1);  /* func+1 == function base */
+    Instruction i = luaG_symbexec(p, pc, stackpos);
+    switch (GET_OPCODE(i)) {
+      case OP_GETGLOBAL: {
+        *name = p->kstr[GETARG_U(i)]->str;
+        return "global";
+      }
+      case OP_GETLOCAL: {
+        *name = luaF_getlocalname(p, GETARG_U(i)+1, pc);
+        return (*name) ? "local" : NULL;
+      }
+      case OP_PUSHSELF:
+      case OP_GETDOTTED: {
+        *name = p->kstr[GETARG_U(i)]->str;
+        return "field";
+      }
+      default:
+        return NULL;  /* no usefull name found */
+    }
+  }
 }
 
 
-void luaG_indexerror (lua_State *L, TObject *t) {
-  call_index_error(L, t, "index");
+/* }====================================================== */
+
+
+static void call_index_error (lua_State *L, StkId o, const char *op,
+                              const char *tp) {
+  const char *name;
+  const char *kind = getname(L, o, &name);
+  if (kind)
+    luaL_verror(L, "%s `%s' is not a %s", kind, name, tp);
+  else
+    luaL_verror(L, "attempt to %.10s a %.10s value", op, lua_type(L, o));
+}
+
+
+void luaG_callerror (lua_State *L, StkId func) {
+  call_index_error(L, func, "call", "function");
+}
+
+
+void luaG_indexerror (lua_State *L, StkId t) {
+  call_index_error(L, t, "index", "table");
 }