simple stuff works with --gc:stack

lib/system.nim

@@ -2565,8 +2565,9 @@ when not defined(JS): #and not defined(nimscript):
   {.push stack_trace: off, profiler:off.}
 
   when not defined(nimscript) and not defined(nogc):
+    when not defined(gcStack):
       proc initGC()
-    when not defined(boehmgc) and not defined(useMalloc) and not defined(gogc):
+    when not defined(boehmgc) and not defined(useMalloc) and not defined(gogc) and not defined(gcStack):
       proc initAllocator() {.inline.}
 
     proc initStackBottom() {.inline, compilerproc.} =

lib/system/gc_stack.nim

@@ -36,33 +36,34 @@ type
   BaseChunk = object
     next: Chunk
     size: int
-    head, last: ptr ObjHeader # first and last object in chunk that
+    head, tail: ptr ObjHeader # first and last object in chunk that
                               # has a finalizer attached to it
 
 type
   StackPtr = object
-    chunk: pointer
+    bump: pointer
     remaining: int
     current: Chunk
 
   MemRegion* = object
     remaining: int
-    chunk: pointer
+    bump: pointer
-    head, last: Chunk
+    head, tail: Chunk
     nextChunkSize, totalSize: int
     hole: ptr Hole # we support individual freeing
+    when hasThreadSupport:
       lock: SysLock
 
 var
-  region {.threadVar.}: MemRegion
+  tlRegion {.threadVar.}: MemRegion
 
 template withRegion*(r: MemRegion; body: untyped) =
-  let oldRegion = region
+  let oldRegion = tlRegion
-  region = r
+  tlRegion = r
   try:
     body
   finally:
-    region = oldRegion
+    tlRegion = oldRegion
 
 template inc(p: pointer, s: int) =
   p = cast[pointer](cast[int](p) +% s)
@@ -71,7 +72,7 @@ template `+!`(p: pointer, s: int): pointer =
   cast[pointer](cast[int](p) +% s)
 
 template `-!`(p: pointer, s: int): pointer =
-  cast[pointer](cast[int](p) +% s)
+  cast[pointer](cast[int](p) -% s)
 
 proc allocSlowPath(r: var MemRegion; size: int) =
   # we need to ensure that the underlying linked list
@@ -84,7 +85,7 @@ proc allocSlowPath(r: var MemRegion; size: int) =
     r.nextChunkSize =
       if r.totalSize < 64 * 1024: PageSize*4
       else: r.nextChunkSize*2
-  var s = align(size+sizeof(BaseChunk), PageSize)
+  var s = roundup(size+sizeof(BaseChunk), PageSize)
   var fresh: Chunk
   if s > r.nextChunkSize:
     fresh = cast[Chunk](osAllocPages(s))
@@ -97,22 +98,25 @@ proc allocSlowPath(r: var MemRegion; size: int) =
     else:
       s = r.nextChunkSize
   fresh.size = s
-  fresh.final = nil
+  fresh.head = nil
-  r.totalSize += s
+  fresh.tail = nil
-  let old = r.last
+  inc r.totalSize, s
+  let old = r.tail
   if old == nil:
     r.head = fresh
   else:
-    r.last.next = fresh
+    r.tail.next = fresh
-  r.chunk = fresh +! sizeof(BaseChunk)
+  r.bump = fresh +! sizeof(BaseChunk)
-  r.last = fresh
+  r.tail = fresh
   r.remaining = s - sizeof(BaseChunk)
 
 proc alloc(r: var MemRegion; size: int): pointer {.inline.} =
-  if unlikely(r.remaining < size): allocSlowPath(r, size)
+  if size > r.remaining:
+    allocSlowPath(r, size)
+  sysAssert(size <= r.remaining, "size <= r.remaining")
   dec(r.remaining, size)
-  result = r.chunk
+  result = r.bump
-  inc r.chunk, size
+  inc r.bump, size
 
 proc runFinalizers(c: Chunk) =
   var it = c.head
@@ -120,63 +124,76 @@ proc runFinalizers(c: Chunk) =
     # indivually freed objects with finalizer stay in the list, but
     # their typ is nil then:
     if it.typ != nil and it.typ.finalizer != nil:
-      (cast[Finalizer](cell.typ.finalizer))(cell+!sizeof(ObjHeader))
+      (cast[Finalizer](it.typ.finalizer))(it+!sizeof(ObjHeader))
-    it = it.next
+    it = it.nextFinal
 
 proc dealloc(r: var MemRegion; p: pointer) =
-  let it = p-!sizeof(ObjHeader)
+  let it = cast[ptr ObjHeader](p-!sizeof(ObjHeader))
   if it.typ != nil and it.typ.finalizer != nil:
-    (cast[Finalizer](cell.typ.finalizer))(p)
+    (cast[Finalizer](it.typ.finalizer))(p)
   it.typ = nil
 
-proc deallocAll(head: Chunk) =
+proc deallocAll(r: var MemRegion; head: Chunk) =
   var it = head
   while it != nil:
+    let nxt = it.next
     runFinalizers(it)
+    dec r.totalSize, it.size
     osDeallocPages(it, it.size)
-    it = it.next
+    it = nxt
 
 proc deallocAll*(r: var MemRegion) =
-  deallocAll(r.head)
+  deallocAll(r, r.head)
   zeroMem(addr r, sizeof r)
 
 proc obstackPtr*(r: MemRegion): StackPtr =
-  result.chunk = r.chunk
+  result.bump = r.bump
   result.remaining = r.remaining
-  result.current = r.last
+  result.current = r.tail
 
-proc setObstackPtr*(r: MemRegion; sp: StackPtr) =
+template computeRemaining(r): untyped =
+  r.tail.size -% (cast[int](r.bump) -% cast[int](r.tail))
+
+proc setObstackPtr*(r: var MemRegion; sp: StackPtr) =
   # free everything after 'sp':
   if sp.current != nil:
-    deallocAll(sp.current.next)
+    deallocAll(r, sp.current.next)
-  r.chunk = sp.chunk
+    sp.current.next = nil
+  else:
+    deallocAll(r, r.head)
+    r.head = nil
+  r.bump = sp.bump
+  r.tail = sp.current
   r.remaining = sp.remaining
-  r.last = sp.current
+
+proc obstackPtr*(): StackPtr = tlRegion.obstackPtr()
+proc setObstackPtr*(sp: StackPtr) = tlRegion.setObstackPtr(sp)
 
 proc joinRegion*(dest: var MemRegion; src: MemRegion) =
   # merging is not hard.
   if dest.head.isNil:
     dest.head = src.head
   else:
-    dest.last.next = src.head
+    dest.tail.next = src.head
-  dest.last = src.last
+  dest.tail = src.tail
-  dest.chunk = src.chunk
+  dest.bump = src.bump
   dest.remaining = src.remaining
   dest.nextChunkSize = max(dest.nextChunkSize, src.nextChunkSize)
-  dest.totalSize += src.totalSize
+  inc dest.totalSize, src.totalSize
-  if dest.hole.size < src.hole.size:
-    dest.hole = src.hole
 
 proc isOnHeap*(r: MemRegion; p: pointer): bool =
-  # the last chunk is the largest, so check it first. It's also special
+  # the tail chunk is the largest, so check it first. It's also special
   # in that contains the current bump pointer:
-  if r.last >= p and p < r.chunk:
+  if r.tail >= p and p < r.bump:
     return true
   var it = r.head
-  while it != r.last:
+  while it != r.tail:
     if it >= p and p <= it+!it.size: return true
     it = it.next
 
+when false:
+  # essential feature for later: copy data over from one region to another
+
   proc isInteriorPointer(r: MemRegion; p: pointer): pointer =
     discard " we cannot patch stack pointers anyway!"
 
@@ -331,17 +348,17 @@ proc rawNewObj(r: var MemRegion, typ: PNimType, size: int): pointer =
   var res = cast[ptr ObjHeader](alloc(r, size + sizeof(ObjHeader)))
   res.typ = typ
   if typ.finalizer != nil:
-    res.nextFinal = r.chunk.head
+    res.nextFinal = r.head.head
-    r.chunk.head = res
+    r.head.head = res
   result = res +! sizeof(ObjHeader)
 
 proc newObj(typ: PNimType, size: int): pointer {.compilerRtl.} =
-  result = rawNewObj(typ, size, region)
+  result = rawNewObj(tlRegion, typ, size)
   zeroMem(result, size)
   when defined(memProfiler): nimProfile(size)
 
 proc newObjNoInit(typ: PNimType, size: int): pointer {.compilerRtl.} =
-  result = rawNewObj(typ, size, region)
+  result = rawNewObj(tlRegion, typ, size)
   when defined(memProfiler): nimProfile(size)
 
 proc newSeq(typ: PNimType, len: int): pointer {.compilerRtl.} =
@@ -351,7 +368,7 @@ proc newSeq(typ: PNimType, len: int): pointer {.compilerRtl.} =
   cast[PGenericSeq](result).reserved = len
 
 proc newObjRC1(typ: PNimType, size: int): pointer {.compilerRtl.} =
-  result = rawNewObj(typ, size, gch)
+  result = rawNewObj(tlRegion, typ, size)
   zeroMem(result, size)
 
 proc newSeqRC1(typ: PNimType, len: int): pointer {.compilerRtl.} =
@@ -360,23 +377,63 @@ proc newSeqRC1(typ: PNimType, len: int): pointer {.compilerRtl.} =
   cast[PGenericSeq](result).len = len
   cast[PGenericSeq](result).reserved = len
 
-proc growObj(old: pointer, newsize: int, gch: var GcHeap): pointer =
+proc growObj(region: var MemRegion; old: pointer, newsize: int): pointer =
-  collectCT(gch)
+  let typ = cast[ptr ObjHeader](old -! sizeof(ObjHeader)).typ
-  var ol = usrToCell(old)
+  result = rawNewObj(region, typ, newsize)
-  sysAssert(ol.typ != nil, "growObj: 1")
+  let elemSize = if typ.kind == tyString: 1 else: typ.base.size
-  gcAssert(ol.typ.kind in {tyString, tySequence}, "growObj: 2")
+  let oldsize = cast[PGenericSeq](old).len*elemSize + GenericSeqSize
-
+  copyMem(result, old, oldsize)
-  var res = cast[PCell](rawAlloc(gch.region, newsize + sizeof(Cell)))
+  zeroMem(result +! oldsize, newsize-oldsize)
-  var elemSize = 1
-  if ol.typ.kind != tyString: elemSize = ol.typ.base.size
-
-  var oldsize = cast[PGenericSeq](old).len*elemSize + GenericSeqSize
-  copyMem(res, ol, oldsize + sizeof(Cell))
-  zeroMem(cast[pointer](cast[ByteAddress](res)+% oldsize +% sizeof(Cell)),
-          newsize-oldsize)
-  sysAssert((cast[ByteAddress](res) and (MemAlign-1)) == 0, "growObj: 3")
-  result = cellToUsr(res)
 
 proc growObj(old: pointer, newsize: int): pointer {.rtl.} =
-  result = growObj(old, newsize, region)
+  result = growObj(tlRegion, old, newsize)
 
+proc unsureAsgnRef(dest: PPointer, src: pointer) {.compilerproc, inline.} =
+  dest[] = src
+proc asgnRef(dest: PPointer, src: pointer) {.compilerproc, inline.} =
+  dest[] = src
+proc asgnRefNoCycle(dest: PPointer, src: pointer) {.compilerproc, inline.} =
+  dest[] = src
+
+proc alloc(size: Natural): pointer =
+  result = cmalloc(size)
+  if result == nil: raiseOutOfMem()
+proc alloc0(size: Natural): pointer =
+  result = alloc(size)
+  zeroMem(result, size)
+proc realloc(p: pointer, newsize: Natural): pointer =
+  result = crealloc(p, newsize)
+  if result == nil: raiseOutOfMem()
+proc dealloc(p: pointer) = cfree(p)
+
+proc allocShared(size: Natural): pointer =
+  result = cmalloc(size)
+  if result == nil: raiseOutOfMem()
+proc allocShared0(size: Natural): pointer =
+  result = alloc(size)
+  zeroMem(result, size)
+proc reallocShared(p: pointer, newsize: Natural): pointer =
+  result = crealloc(p, newsize)
+  if result == nil: raiseOutOfMem()
+proc deallocShared(p: pointer) = cfree(p)
+
+when hasThreadSupport:
+  proc getFreeSharedMem(): int = 0
+  proc getTotalSharedMem(): int = 0
+  proc getOccupiedSharedMem(): int = 0
+
+proc GC_disable() = discard
+proc GC_enable() = discard
+proc GC_fullCollect() = discard
+proc GC_setStrategy(strategy: GC_Strategy) = discard
+proc GC_enableMarkAndSweep() = discard
+proc GC_disableMarkAndSweep() = discard
+proc GC_getStatistics(): string = return ""
+
+proc getOccupiedMem(): int =
+  result = tlRegion.totalSize - tlRegion.remaining
+proc getFreeMem(): int = tlRegion.remaining
+proc getTotalMem(): int =
+  result = tlRegion.totalSize
+
+proc setStackBottom(theStackBottom: pointer) = discard

lib/system/mmdisp.nim

@@ -511,6 +511,7 @@ elif defined(nogc):
   include "system/cellsets"
 
 else:
+  when not defined(gcStack):
     include "system/alloc"
 
     include "system/cellsets"

lib/system/sysstr.nim

@@ -228,7 +228,8 @@ proc setLengthSeq(seq: PGenericSeq, elemSize, newLen: int): PGenericSeq {.
   elif newLen < result.len:
     # we need to decref here, otherwise the GC leaks!
     when not defined(boehmGC) and not defined(nogc) and
-         not defined(gcMarkAndSweep) and not defined(gogc):
+         not defined(gcMarkAndSweep) and not defined(gogc) and
+         not defined(gcStack):
       when false: # compileOption("gc", "v2"):
         for i in newLen..result.len-1:
           let len0 = gch.tempStack.len