1 files changed, 53 insertions, 0 deletions
diff --git a/lib/system/gc_hooks.nim b/lib/system/gc_hooks.nim
new file mode 100644
index 000000000..ace62eea0
--- /dev/null
+++ b/lib/system/gc_hooks.nim
@@ -0,0 +1,53 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2019 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
+
+## Hooks for memory management. Can be used to implement custom garbage
+## collectors etc.
+
+type
+  GlobalMarkerProc = proc () {.nimcall, benign, raises: [], tags: [].}
+var
+  globalMarkersLen: int
+  globalMarkers: array[0..3499, GlobalMarkerProc]
+  threadLocalMarkersLen: int
+  threadLocalMarkers: array[0..3499, GlobalMarkerProc]
+
+proc nimRegisterGlobalMarker(markerProc: GlobalMarkerProc) {.compilerproc.} =
+  if globalMarkersLen <= high(globalMarkers):
+    globalMarkers[globalMarkersLen] = markerProc
+    inc globalMarkersLen
+  else:
+    cstderr.rawWrite("[GC] cannot register global variable; too many global variables")
+    rawQuit 1
+
+proc nimRegisterThreadLocalMarker(markerProc: GlobalMarkerProc) {.compilerproc.} =
+  if threadLocalMarkersLen <= high(threadLocalMarkers):
+    threadLocalMarkers[threadLocalMarkersLen] = markerProc
+    inc threadLocalMarkersLen
+  else:
+    cstderr.rawWrite("[GC] cannot register thread local variable; too many thread local variables")
+    rawQuit 1
+
+proc traverseGlobals*() =
+  for i in 0..globalMarkersLen-1:
+    globalMarkers[i]()
+
+proc traverseThreadLocals*() =
+  for i in 0..threadLocalMarkersLen-1:
+    threadLocalMarkers[i]()
+
+var
+  newObjHook*: proc (typ: PNimType, size: int): pointer {.nimcall, tags: [], raises: [], gcsafe.}
+  traverseObjHook*: proc (p: pointer, op: int) {.nimcall, tags: [], raises: [], gcsafe.}
+
+proc nimGCvisit(p: pointer, op: int) {.inl, compilerRtl.} =
+  traverseObjHook(p, op)
+
+proc newObj(typ: PNimType, size: int): pointer {.inl, compilerRtl.} =
+  result = newObjHook(typ, size)