hotfix for --gc:regions

lib/system/gc_regions.nim

@@ -162,6 +162,7 @@ proc allocFast(r: var MemRegion; size: int): pointer =
           return pointer(it)
         prev = it
         it = it.next
+  let size = roundup(size, MemAlign)
   if size > r.remaining:
     allocSlowPath(r, size)
   sysAssert(size <= r.remaining, "size <= r.remaining")
@@ -288,11 +289,13 @@ proc rawNewSeq(r: var MemRegion, typ: PNimType, size: int): pointer =
   result = res +! sizeof(SeqHeader)
 
 proc newObj(typ: PNimType, size: int): pointer {.compilerRtl.} =
+  sysAssert typ.kind notin {tySequence, tyString}, "newObj cannot be used to construct seqs"
   result = rawNewObj(tlRegion, typ, size)
   zeroMem(result, size)
   when defined(memProfiler): nimProfile(size)
 
 proc newObjNoInit(typ: PNimType, size: int): pointer {.compilerRtl.} =
+  sysAssert typ.kind notin {tySequence, tyString}, "newObj cannot be used to construct seqs"
   result = rawNewObj(tlRegion, typ, size)
   when defined(memProfiler): nimProfile(size)
 

lib/system/mmdisp.nim

@@ -561,13 +561,16 @@ else:
 
 when not declared(nimNewSeqOfCap):
   proc nimNewSeqOfCap(typ: PNimType, cap: int): pointer {.compilerproc.} =
-    let s = addInt(mulInt(cap, typ.base.size), GenericSeqSize)
-    when declared(newObjNoInit):
-      result = if ntfNoRefs in typ.base.flags: newObjNoInit(typ, s) else: newObj(typ, s)
+    when defined(gcRegions):
+      result = newStr(typ, cap, ntfNoRefs notin typ.base.flags)
     else:
-      result = newObj(typ, s)
-    cast[PGenericSeq](result).len = 0
-    cast[PGenericSeq](result).reserved = cap
+      let s = addInt(mulInt(cap, typ.base.size), GenericSeqSize)
+      when declared(newObjNoInit):
+        result = if ntfNoRefs in typ.base.flags: newObjNoInit(typ, s) else: newObj(typ, s)
+      else:
+        result = newObj(typ, s)
+      cast[PGenericSeq](result).len = 0
+      cast[PGenericSeq](result).reserved = cap
 
 {.pop.}