gc: destructors is beginning to work (#10483)

* kochdocs.nim: code cleanup
* docgen: nicer indentation
* parser.nim: code cleanup
* fixes #10458
* make tests green again
* make =destroy mixins
* gc:destructors: produced C code is almost working
* --gc:destructors simple program compiles (but leaks memory)
* gc:destructors make examples compile in C++ mode
* destructors: string implementation bugfixes
* strs.nim: minor code cleanup
* destructors: builtin seqs are beginning to work
* remove debugging helpers

3 files changed, 30 insertions, 15 deletions

diff --git a/lib/system/excpt.nim b/lib/system/excpt.nim
index cc0c1f54b..f2f82c3b8 100644
--- a/lib/system/excpt.nim
+++ b/lib/system/excpt.nim
@@ -220,11 +220,12 @@ proc auxWriteStackTrace(f: PFrame; s: var seq[StackTraceEntry]) =
     inc(i)
     it = it.prev
   var last = i-1
-  if s.len == 0:
-    s = newSeq[StackTraceEntry](i)
-  else:
-    last = s.len + i - 1
-    s.setLen(last+1)
+  when true: # not defined(gcDestructors):
+    if s.len == 0:
+      s = newSeq[StackTraceEntry](i)
+    else:
+      last = s.len + i - 1
+      s.setLen(last+1)
   it = f
   while it != nil:
     s[last] = StackTraceEntry(procname: it.procname,
@@ -440,11 +441,13 @@ proc getStackTrace(e: ref Exception): string =
   else:
     result = ""
 
-when not defined(gcDestructors):
-  proc getStackTraceEntries*(e: ref Exception): seq[StackTraceEntry] =
-    ## Returns the attached stack trace to the exception ``e`` as
-    ## a ``seq``. This is not yet available for the JS backend.
+proc getStackTraceEntries*(e: ref Exception): seq[StackTraceEntry] =
+  ## Returns the attached stack trace to the exception ``e`` as
+  ## a ``seq``. This is not yet available for the JS backend.
+  when not defined(gcDestructors):
     shallowCopy(result, e.trace)
+  else:
+    result = move(e.trace)
 
 const nimCallDepthLimit {.intdefine.} = 2000
 
diff --git a/lib/system/gc_regions.nim b/lib/system/gc_regions.nim
index 59f68918f..797eeeebf 100644
--- a/lib/system/gc_regions.nim
+++ b/lib/system/gc_regions.nim
@@ -195,6 +195,19 @@ proc runFinalizers(c: Chunk) =
       (cast[Finalizer](it.typ.finalizer))(it+!sizeof(ObjHeader))
     it = it.nextFinal
 
+proc runFinalizers(c: Chunk; newbump: pointer) =
+  var it = c.head
+  var prev: ptr ObjHeader = nil
+  while it != nil:
+    let nxt = it.nextFinal
+    if it >= newbump:
+      if it.typ != nil and it.typ.finalizer != nil:
+        (cast[Finalizer](it.typ.finalizer))(it+!sizeof(ObjHeader))
+    elif prev != nil:
+      prev.nextFinal = nil
+    prev = it
+    it = nxt
+
 proc dealloc(r: var MemRegion; p: pointer; size: int) =
   let it = cast[ptr ObjHeader](p-!sizeof(ObjHeader))
   if it.typ != nil and it.typ.finalizer != nil:
@@ -237,16 +250,15 @@ template computeRemaining(r): untyped =
 
 proc setObstackPtr*(r: var MemRegion; sp: StackPtr) =
   # free everything after 'sp':
-  if sp.current.next != nil:
+  if sp.current != nil and sp.current.next != nil:
     deallocAll(r, sp.current.next)
     sp.current.next = nil
     when false:
       # better leak this memory than be sorry:
       for i in 0..high(r.freeLists): r.freeLists[i] = nil
       r.holes = nil
-  #else:
-  #  deallocAll(r, r.head)
-  #  r.head = nil
+  if r.tail != nil: runFinalizers(r.tail, sp.bump)
+
   r.bump = sp.bump
   r.tail = sp.current
   r.remaining = sp.remaining
diff --git a/lib/system/helpers2.nim b/lib/system/helpers2.nim
index c67a2c278..8bd69ad71 100644
--- a/lib/system/helpers2.nim
+++ b/lib/system/helpers2.nim
@@ -1,7 +1,7 @@
 # imported by other modules, unlike helpers.nim which is included
 
 template formatErrorIndexBound*[T](i, a, b: T): string =
-  "index out of bounds: (a:" & $a & ") <= (i:" & $i & ") <= (b:" & $b & ") "
+  "index out of bounds: (a: " & $a & ") <= (i: " & $i & ") <= (b: " & $b & ") "
 
 template formatErrorIndexBound*[T](i, n: T): string =
-  "index out of bounds: (i:" & $i & ") <= (n:" & $n & ") "
+  "index out of bounds: (i: " & $i & ") <= (n: " & $n & ") "