track call depth separately from loop count in VM

compiler/commands.nim

@@ -919,6 +919,12 @@ proc processSwitch*(switch, arg: string, pass: TCmdLinePass, info: TLineInfo;
     discard parseSaturatedNatural(arg, value)
     if not value > 0: localError(conf, info, "maxLoopIterationsVM must be a positive integer greater than zero")
     conf.maxLoopIterationsVM = value
+  of "maxcalldepthvm":
+    expectArg(conf, switch, arg, pass, info)
+    var value: int = 2_000
+    discard parseSaturatedNatural(arg, value)
+    if value <= 0: localError(conf, info, "maxCallDepthVM must be a positive integer greater than zero")
+    conf.maxCallDepthVM = value
   of "errormax":
     expectArg(conf, switch, arg, pass, info)
     # Note: `nim check` (etc) can overwrite this.

compiler/options.nim

@@ -385,6 +385,7 @@ type
     warnCounter*: int
     errorMax*: int
     maxLoopIterationsVM*: int ## VM: max iterations of all loops
+    maxCallDepthVM*: int ## VM: max call depth
     isVmTrace*: bool
     configVars*: StringTableRef
     symbols*: StringTableRef ## We need to use a StringTableRef here as defined
@@ -600,6 +601,7 @@ proc newConfigRef*(): ConfigRef =
     arguments: "",
     suggestMaxResults: 10_000,
     maxLoopIterationsVM: 10_000_000,
+    maxCallDepthVM: 2_000,
     vmProfileData: newProfileData(),
     spellSuggestMax: spellSuggestSecretSauce,
     currentConfigDir: ""

compiler/vm.nim

@@ -516,6 +516,8 @@ const
   errIllegalConvFromXtoY = "illegal conversion from '$1' to '$2'"
   errTooManyIterations = "interpretation requires too many iterations; " &
     "if you are sure this is not a bug in your code, compile with `--maxLoopIterationsVM:number` (current value: $1)"
+  errCallDepthExceeded = "maximum call depth for the VM exceeded; " &
+    "if you are sure this is not a bug in your code, compile with `--maxCallDepthVM:number` (current value: $1)"
   errFieldXNotFound = "node lacks field: "
 
 
@@ -590,6 +592,7 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
       let newPc = c.cleanUpOnReturn(tos)
       # Perform any cleanup action before returning
       if newPc < 0:
+        inc(c.callDepth)
         pc = tos.comesFrom
         let retVal = regs[0]
         tos = tos.next
@@ -1445,6 +1448,14 @@ proc rawExecute(c: PCtx, start: int, tos: PStackFrame): TFullReg =
           newFrame.slots[i] = regs[rb+i]
         if isClosure:
           newFrame.slots[rc] = TFullReg(kind: rkNode, node: regs[rb].node[1])
+        if c.callDepth <= 0:
+          if allowInfiniteRecursion in c.features:
+            c.callDepth = c.config.maxCallDepthVM
+          else:
+            msgWriteln(c.config, "stack trace: (most recent call last)", {msgNoUnitSep})
+            stackTraceAux(c, tos, pc)
+            globalError(c.config, c.debug[pc], errCallDepthExceeded % $c.config.maxCallDepthVM)
+        dec(c.callDepth)
         tos = newFrame
         updateRegsAlias
         # -1 for the following 'inc pc'
@@ -2311,6 +2322,7 @@ proc execute(c: PCtx, start: int): PNode =
 
 proc execProc*(c: PCtx; sym: PSym; args: openArray[PNode]): PNode =
   c.loopIterations = c.config.maxLoopIterationsVM
+  c.callDepth = c.config.maxCallDepthVM
   if sym.kind in routineKinds:
     if sym.typ.paramsLen != args.len:
       result = nil

compiler/vmdef.nim

@@ -201,6 +201,7 @@ type
   TSandboxFlag* = enum        ## what the evaluation engine should allow
     allowCast,                ## allow unsafe language feature: 'cast'
     allowInfiniteLoops        ## allow endless loops
+    allowInfiniteRecursion    ## allow infinite recursion
   TSandboxFlags* = set[TSandboxFlag]
 
   TSlotKind* = enum   # We try to re-use slots in a smart way to
@@ -257,7 +258,7 @@ type
     mode*: TEvalMode
     features*: TSandboxFlags
     traceActive*: bool
-    loopIterations*: int
+    loopIterations*, callDepth*: int
     comesFromHeuristic*: TLineInfo # Heuristic for better macro stack traces
     callbacks*: seq[VmCallback]
     callbackIndex*: Table[string, int]
@@ -294,13 +295,15 @@ proc newCtx*(module: PSym; cache: IdentCache; g: ModuleGraph; idgen: IdGenerator
   PCtx(code: @[], debug: @[],
     globals: newNode(nkStmtListExpr), constants: newNode(nkStmtList), types: @[],
     prc: PProc(blocks: @[]), module: module, loopIterations: g.config.maxLoopIterationsVM,
+    callDepth: g.config.maxCallDepthVM,
     comesFromHeuristic: unknownLineInfo, callbacks: @[], callbackIndex: initTable[string, int](), errorFlag: "",
     cache: cache, config: g.config, graph: g, idgen: idgen)
 
 proc refresh*(c: PCtx, module: PSym; idgen: IdGenerator) =
   c.module = module
   c.prc = PProc(blocks: @[])
   c.loopIterations = c.config.maxLoopIterationsVM
+  c.callDepth = c.config.maxCallDepthVM
   c.idgen = idgen
 
 proc reverseName(s: string): string =

doc/advopt.txt

@@ -165,6 +165,7 @@ Advanced options:
   --verbosity:0|1|2|3       set Nim's verbosity level (1 is default)
   --errorMax:N              stop compilation after N errors; 0 means unlimited
   --maxLoopIterationsVM:N   set max iterations for all VM loops
+  --maxCallDepthVM:N        set max call depth in the VM
   --experimental:$1
                             enable experimental language feature
   --legacy:$2

tests/vm/tinfiniterecursion.nim

@@ -0,0 +1,9 @@
+proc foo(x: int) =
+  if x < 0:
+    echo "done"
+  else:
+    foo(x + 1) #[tt.Error
+       ^ maximum call depth for the VM exceeded; if you are sure this is not a bug in your code, compile with `--maxCallDepthVM:number` (current value: 2000)]#
+
+static:
+  foo(1)