remove noop option `gc:v2` (#19810)

* remove noop option gc:v2

* changelog

6 files changed, 7 insertions, 18 deletions

diff --git a/changelog.md b/changelog.md
index 6bd3c99e3..98655eaa3 100644
--- a/changelog.md
+++ b/changelog.md
@@ -24,6 +24,8 @@ becomes an alias for `addr`.
 
 - io is about to move out of system; use `-d:nimPreviewSlimSystem` and import `std/syncio`.
 
+- The `gc:v2` option is removed.
+
 ## Standard library additions and changes
 
 [//]: # "Changes:"
diff --git a/compiler/ccgstmts.nim b/compiler/ccgstmts.nim
index 240fa55c8..e791318ee 100644
--- a/compiler/ccgstmts.nim
+++ b/compiler/ccgstmts.nim
@@ -16,7 +16,7 @@ const
     # above X strings a hash-switch for strings is generated
 
 proc getTraverseProc(p: BProc, v: PSym): Rope =
-  if p.config.selectedGC in {gcMarkAndSweep, gcHooks, gcV2, gcRefc} and
+  if p.config.selectedGC in {gcMarkAndSweep, gcHooks, gcRefc} and
       optOwnedRefs notin p.config.globalOptions and
       containsGarbageCollectedRef(v.loc.t):
     # we register a specialized marked proc here; this has the advantage
diff --git a/compiler/ccgtypes.nim b/compiler/ccgtypes.nim
index c5b4d3857..7c26db40d 100644
--- a/compiler/ccgtypes.nim
+++ b/compiler/ccgtypes.nim
@@ -1483,12 +1483,12 @@ proc genTypeInfoV1(m: BModule, t: PType; info: TLineInfo): Rope =
       genTupleInfo(m, x, x, result, info)
   of tySequence:
     genTypeInfoAux(m, t, t, result, info)
-    if m.config.selectedGC in {gcMarkAndSweep, gcRefc, gcV2, gcGo}:
+    if m.config.selectedGC in {gcMarkAndSweep, gcRefc, gcGo}:
       let markerProc = genTraverseProc(m, origType, sig)
       m.s[cfsTypeInit3].addf("$1.marker = $2;$n", [tiNameForHcr(m, result), markerProc])
   of tyRef:
     genTypeInfoAux(m, t, t, result, info)
-    if m.config.selectedGC in {gcMarkAndSweep, gcRefc, gcV2, gcGo}:
+    if m.config.selectedGC in {gcMarkAndSweep, gcRefc, gcGo}:
       let markerProc = genTraverseProc(m, origType, sig)
       m.s[cfsTypeInit3].addf("$1.marker = $2;$n", [tiNameForHcr(m, result), markerProc])
   of tyPtr, tyRange, tyUncheckedArray: genTypeInfoAux(m, t, t, result, info)
diff --git a/compiler/commands.nim b/compiler/commands.nim
index 2e08ad615..31e637aba 100644
--- a/compiler/commands.nim
+++ b/compiler/commands.nim
@@ -262,7 +262,6 @@ proc testCompileOptionArg*(conf: ConfigRef; switch, arg: string, info: TLineInfo
     of "go": result = conf.selectedGC == gcGo
     of "none": result = conf.selectedGC == gcNone
     of "stack", "regions": result = conf.selectedGC == gcRegions
-    of "v2", "generational": warningOptionNoop(arg)
     else: localError(conf, info, errNoneBoehmRefcExpectedButXFound % arg)
   of "opt":
     case arg.normalize
@@ -568,7 +567,6 @@ proc processMemoryManagementOption(switch, arg: string, pass: TCmdLinePass,
       unregisterArcOrc(conf)
       conf.selectedGC = gcRegions
       defineSymbol(conf.symbols, "gcregions")
-    of "v2": warningOptionNoop(arg)
     else: localError(conf, info, errNoneBoehmRefcExpectedButXFound % arg)
 
 proc processSwitch*(switch, arg: string, pass: TCmdLinePass, info: TLineInfo;
diff --git a/compiler/options.nim b/compiler/options.nim
index 545dfb1d1..89fb66d5f 100644
--- a/compiler/options.nim
+++ b/compiler/options.nim
@@ -183,7 +183,6 @@ type
     gcMarkAndSweep = "markAndSweep"
     gcHooks = "hooks"
     gcRefc = "refc"
-    gcV2 = "v2"
     gcGo = "go"
     # gcRefc and the GCs that follow it use a write barrier,
     # as far as usesWriteBarrier() is concerned
diff --git a/lib/system/sysstr.nim b/lib/system/sysstr.nim
index 49fff41e9..c4f0db718 100644
--- a/lib/system/sysstr.nim
+++ b/lib/system/sysstr.nim
@@ -304,20 +304,10 @@ proc setLengthSeq(seq: PGenericSeq, elemSize, elemAlign, newLen: int): PGenericS
     when not defined(boehmGC) and not defined(nogc) and
          not defined(gcMarkAndSweep) and not defined(gogc) and
          not defined(gcRegions):
-      when false: # deadcode: was used by `compileOption("gc", "v2")`
+      if ntfNoRefs notin extGetCellType(result).base.flags:
         for i in newLen..result.len-1:
-          let len0 = gch.tempStack.len
           forAllChildrenAux(dataPointer(result, elemAlign, elemSize, i),
-                            extGetCellType(result).base, waPush)
-          let len1 = gch.tempStack.len
-          for i in len0 ..< len1:
-            doDecRef(gch.tempStack.d[i], LocalHeap, MaybeCyclic)
-          gch.tempStack.len = len0
-      else:
-        if ntfNoRefs notin extGetCellType(result).base.flags:
-          for i in newLen..result.len-1:
-            forAllChildrenAux(dataPointer(result, elemAlign, elemSize, i),
-                              extGetCellType(result).base, waZctDecRef)
+                            extGetCellType(result).base, waZctDecRef)
 
     # XXX: zeroing out the memory can still result in crashes if a wiped-out
     # cell is aliased by another pointer (ie proc parameter or a let variable).