fixes #13881

* fixes #13881
* documented changed requirements for system.onThreadDestruction
* destructors.rst: update the documentation

lib/system/excpt.nim

@@ -493,6 +493,14 @@ proc reraiseException() {.compilerRtl.} =
     else:
       raiseExceptionAux(currException)
 
+proc threadTrouble() =
+  # also forward declared, it is 'raises: []' hence the try-except.
+  try:
+    if currException != nil: reportUnhandledError(currException)
+  except:
+    discard
+  quit 1
+
 proc writeStackTrace() =
   when hasSomeStackTrace:
     var s = ""

lib/system/gc.nim

@@ -843,9 +843,10 @@ when not defined(useNimRtl):
   proc GC_disable() =
     inc(gch.recGcLock)
   proc GC_enable() =
-    if gch.recGcLock <= 0:
-      raise newException(AssertionDefect,
-          "API usage error: GC_enable called but GC is already enabled")
+    when defined(nimDoesntTrackDefects):
+      if gch.recGcLock <= 0:
+        raise newException(AssertionDefect,
+            "API usage error: GC_enable called but GC is already enabled")
     dec(gch.recGcLock)
 
   proc GC_setStrategy(strategy: GC_Strategy) =

lib/system/gc_interface.nim

@@ -14,7 +14,7 @@ when hasAlloc:
       gcOptimizeSpace    ## optimize for memory footprint
 
 when hasAlloc and not defined(js) and not usesDestructors:
-  proc GC_disable*() {.rtl, inl, benign.}
+  proc GC_disable*() {.rtl, inl, benign, raises: [].}
     ## Disables the GC. If called `n` times, `n` calls to `GC_enable`
     ## are needed to reactivate the GC.
     ##
@@ -22,7 +22,7 @@ when hasAlloc and not defined(js) and not usesDestructors:
     ## the mark and sweep phase with
     ## `GC_disableMarkAndSweep <#GC_disableMarkAndSweep>`_.
 
-  proc GC_enable*() {.rtl, inl, benign.}
+  proc GC_enable*() {.rtl, inl, benign, raises: [].}
     ## Enables the GC again.
 
   proc GC_fullCollect*() {.rtl, benign.}
@@ -54,7 +54,7 @@ when hasAlloc and not defined(js) and not usesDestructors:
   proc GC_unref*(x: string) {.magic: "GCunref", benign.}
     ## See the documentation of `GC_ref <#GC_ref,string>`_.
 
-  proc nimGC_setStackBottom*(theStackBottom: pointer) {.compilerRtl, noinline, benign.}
+  proc nimGC_setStackBottom*(theStackBottom: pointer) {.compilerRtl, noinline, benign, raises: [].}
     ## Expands operating GC stack range to `theStackBottom`. Does nothing
       ## if current stack bottom is already lower than `theStackBottom`.
 

lib/system/gc_ms.nim

@@ -495,9 +495,10 @@ when not defined(useNimRtl):
   proc GC_disable() =
     inc(gch.recGcLock)
   proc GC_enable() =
-    if gch.recGcLock <= 0:
-      raise newException(AssertionDefect,
-          "API usage error: GC_enable called but GC is already enabled")
+    when defined(nimDoesntTrackDefects):
+      if gch.recGcLock <= 0:
+        raise newException(AssertionDefect,
+            "API usage error: GC_enable called but GC is already enabled")
     dec(gch.recGcLock)
 
   proc GC_setStrategy(strategy: GC_Strategy) = discard

lib/system/threads.nim

@@ -89,9 +89,9 @@ type
       data: TArg
 
 var
-  threadDestructionHandlers {.rtlThreadVar.}: seq[proc () {.closure, gcsafe.}]
+  threadDestructionHandlers {.rtlThreadVar.}: seq[proc () {.closure, gcsafe, raises: [].}]
 
-proc onThreadDestruction*(handler: proc () {.closure, gcsafe.}) =
+proc onThreadDestruction*(handler: proc () {.closure, gcsafe, raises: [].}) =
   ## Registers a *thread local* handler that is called at the thread's
   ## destruction.
   ##
@@ -105,7 +105,10 @@ template afterThreadRuns() =
     threadDestructionHandlers[i]()
 
 when not defined(boehmgc) and not hasSharedHeap and not defined(gogc) and not defined(gcRegions):
-  proc deallocOsPages() {.rtl.}
+  proc deallocOsPages() {.rtl, raises: [].}
+
+proc threadTrouble() {.raises: [].}
+  ## defined in system/excpt.nim
 
 when defined(boehmgc):
   type GCStackBaseProc = proc(sb: pointer, t: pointer) {.noconv.}
@@ -116,7 +119,7 @@ when defined(boehmgc):
   proc boehmGC_unregister_my_thread()
     {.importc: "GC_unregister_my_thread", boehmGC.}
 
-  proc threadProcWrapDispatch[TArg](sb: pointer, thrd: pointer) {.noconv.} =
+  proc threadProcWrapDispatch[TArg](sb: pointer, thrd: pointer) {.noconv, raises: [].} =
     boehmGC_register_my_thread(sb)
     try:
       let thrd = cast[ptr Thread[TArg]](thrd)
@@ -124,11 +127,13 @@ when defined(boehmgc):
         thrd.dataFn()
       else:
         thrd.dataFn(thrd.data)
+    except:
+      threadTrouble()
     finally:
       afterThreadRuns()
     boehmGC_unregister_my_thread()
 else:
-  proc threadProcWrapDispatch[TArg](thrd: ptr Thread[TArg]) =
+  proc threadProcWrapDispatch[TArg](thrd: ptr Thread[TArg]) {.raises: [].} =
     try:
       when TArg is void:
         thrd.dataFn()
@@ -139,21 +144,22 @@ else:
           var x: TArg
           deepCopy(x, thrd.data)
           thrd.dataFn(x)
+    except:
+      threadTrouble()
     finally:
       afterThreadRuns()
 
-proc threadProcWrapStackFrame[TArg](thrd: ptr Thread[TArg]) =
+proc threadProcWrapStackFrame[TArg](thrd: ptr Thread[TArg]) {.raises: [].} =
   when defined(boehmgc):
     boehmGC_call_with_stack_base(threadProcWrapDispatch[TArg], thrd)
   elif not defined(nogc) and not defined(gogc) and not defined(gcRegions) and not usesDestructors:
-    var p {.volatile.}: proc(a: ptr Thread[TArg]) {.nimcall, gcsafe.} =
-      threadProcWrapDispatch[TArg]
+    var p {.volatile.}: pointer
     # init the GC for refc/markandsweep
     nimGC_setStackBottom(addr(p))
     initGC()
     when declared(threadType):
       threadType = ThreadType.NimThread
-    p(thrd)
+    threadProcWrapDispatch[TArg](thrd)
     when declared(deallocOsPages): deallocOsPages()
   else:
     threadProcWrapDispatch(thrd)