Prevent infinite recursion for eval, alias

Signed-off-by: Steve Bennett <steveb@workware.net.au>

jim.c

@@ -5051,7 +5051,8 @@ Jim_Interp *Jim_CreateInterp(void)
 
     memset(i, 0, sizeof(*i));
 
-    i->maxNestingDepth = JIM_MAX_NESTING_DEPTH;
+    i->maxCallFrameDepth = JIM_MAX_CALLFRAME_DEPTH;
+    i->maxEvalDepth = JIM_MAX_EVAL_DEPTH;
     i->lastCollectTime = time(NULL);
 
     /* Note that we can create objects only after the
@@ -9676,6 +9677,35 @@ static int JimUnknown(Jim_Interp *interp, int argc, Jim_Obj *const *argv, Jim_Ob
     return retCode;
 }
 
+static int JimInvokeCommand(Jim_Interp *interp, Jim_Cmd *cmdPtr, Jim_Obj *fileNameObj, int linenr, int objc, Jim_Obj *const *objv)
+{
+    int retcode;
+
+    if (cmdPtr == NULL) {
+        return JimUnknown(interp, objc, objv, fileNameObj, linenr);
+    }
+    if (interp->evalDepth == interp->maxEvalDepth) {
+        Jim_SetResultString(interp, "Infinite eval recursion", -1);
+        return JIM_ERR;
+    }
+    interp->evalDepth++;
+
+    /* Call it -- Make sure result is an empty object. */
+    JimIncrCmdRefCount(cmdPtr);
+    Jim_SetEmptyResult(interp);
+    if (cmdPtr->isproc) {
+        retcode = JimCallProcedure(interp, cmdPtr, fileNameObj, linenr, objc, objv);
+    }
+    else {
+        interp->cmdPrivData = cmdPtr->u.native.privData;
+        retcode = cmdPtr->u.native.cmdProc(interp, objc, objv);
+    }
+    JimDecrCmdRefCount(interp, cmdPtr);
+    interp->evalDepth--;
+
+    return retcode;
+}
+
 /* Eval the object vector 'objv' composed of 'objc' elements.
  * Every element is used as single argument.
  * Jim_EvalObj() will call this function every time its object
@@ -9694,24 +9724,11 @@ static int JimEvalObjVector(Jim_Interp *interp, int objc, Jim_Obj *const *objv,
     /* Incr refcount of arguments. */
     for (i = 0; i < objc; i++)
         Jim_IncrRefCount(objv[i]);
+
     /* Command lookup */
     cmdPtr = Jim_GetCommand(interp, objv[0], JIM_ERRMSG);
-    if (cmdPtr == NULL) {
-        retcode = JimUnknown(interp, objc, objv, fileNameObj, linenr);
-    }
-    else {
-        /* Call it -- Make sure result is an empty object. */
-        JimIncrCmdRefCount(cmdPtr);
-        Jim_SetEmptyResult(interp);
-        if (cmdPtr->isproc) {
-            retcode = JimCallProcedure(interp, cmdPtr, fileNameObj, linenr, objc, objv);
-        }
-        else {
-            interp->cmdPrivData = cmdPtr->u.native.privData;
-            retcode = cmdPtr->u.native.cmdProc(interp, objc, objv);
-        }
-        JimDecrCmdRefCount(interp, cmdPtr);
-    }
+    retcode = JimInvokeCommand(interp, cmdPtr, fileNameObj, linenr, objc, objv);
+
     /* Decr refcount of arguments and return the retcode */
     for (i = 0; i < objc; i++)
         Jim_DecrRefCount(interp, objv[i]);
@@ -10131,23 +10148,7 @@ int Jim_EvalObj(Jim_Interp *interp, Jim_Obj *scriptObjPtr)
         if (retcode == JIM_OK && argc) {
             /* Lookup the command to call */
             cmd = Jim_GetCommand(interp, argv[0], JIM_ERRMSG);
-            if (cmd != NULL) {
-                /* Call it -- Make sure result is an empty object. */
-                JimIncrCmdRefCount(cmd);
-                Jim_SetEmptyResult(interp);
-                if (cmd->isproc) {
-                    retcode =
-                        JimCallProcedure(interp, cmd, script->fileNameObj, linenr, argc, argv);
-                } else {
-                    interp->cmdPrivData = cmd->u.native.privData;
-                    retcode = cmd->u.native.cmdProc(interp, argc, argv);
-                }
-                JimDecrCmdRefCount(interp, cmd);
-            }
-            else {
-                /* Call [unknown] */
-                retcode = JimUnknown(interp, argc, argv, script->fileNameObj, linenr);
-            }
+            retcode = JimInvokeCommand(interp, cmd, script->fileNameObj, linenr, argc, argv);
             if (interp->signal_level && interp->sigmask) {
                 /* Check for a signal after each command */
                 retcode = JIM_SIGNAL;
@@ -10274,7 +10275,7 @@ static int JimCallProcedure(Jim_Interp *interp, Jim_Cmd *cmd, Jim_Obj *fileNameO
     }
 
     /* Check if there are too nested calls */
-    if (interp->framePtr->level == interp->maxNestingDepth) {
+    if (interp->framePtr->level == interp->maxCallFrameDepth) {
         Jim_SetResultString(interp, "Too many nested calls. Infinite recursion?", -1);
         return JIM_ERR;
     }

jim.h

@@ -140,7 +140,8 @@ extern "C" {
 /* The following are internal codes and should never been seen/used */
 #define JIM_EVAL 7
 
-#define JIM_MAX_NESTING_DEPTH 1000 /* default max nesting depth */
+#define JIM_MAX_CALLFRAME_DEPTH 1000 /* default max nesting depth for procs */
+#define JIM_MAX_EVAL_DEPTH 2000 /* default max nesting depth for eval */
 
 /* Some function get an integer argument with flags to change
  * the behaviour. */
@@ -517,7 +518,9 @@ typedef struct Jim_Interp {
     int errorLine; /* Error line where an error occurred. */
     Jim_Obj *errorFileNameObj; /* Error file where an error occurred. */
     int addStackTrace; /* > 0 If a level should be added to the stack trace */
-    int maxNestingDepth; /* Used for infinite loop detection. */
+    int maxCallFrameDepth; /* Used for infinite loop detection. */
+    int maxEvalDepth; /* Used for infinite loop detection. */
+    int evalDepth;  /* Current eval depth */
     int returnCode; /* Completion code to return on JIM_RETURN. */
     int returnLevel; /* Current level of 'return -level' */
     int exitCode; /* Code to return to the OS on JIM_EXIT. */

regtest.tcl

@@ -178,6 +178,24 @@ catch {
 incr globx
 puts "TEST 25 PASSED"
 
+# REGTEST 26
+# 2 Dec 2011 - infinite eval recursion
+catch {
+    set x 0
+    set y {incr x; eval $y}
+    eval $y
+} msg
+puts "TEST 26 PASSED"
+
+# REGTEST 27
+# 2 Dec 2011 - infinite alias recursion
+catch {
+    proc p {} {}
+    alias p p
+    p
+} msg
+puts "TEST 27 PASSED"
+
 # TAKE THE FOLLOWING puts AS LAST LINE
 
 puts "--- ALL TESTS PASSED ---"