enable vtable implementation for C++

compiler/ccgtypes.nim

@@ -1678,6 +1678,13 @@ proc genDisplay(m: BModule; t: PType, depth: int): Rope =
   result.add seqs[0]
   result.add "}"
 
+proc genVTable(seqs: seq[PSym]): string =
+  result = "{"
+  for i in 0..<seqs.len:
+    if i > 0: result.add ", "
+    result.add "(void *) " & seqs[i].loc.r
+  result.add "}"
+
 proc genTypeInfoV2OldImpl(m: BModule; t, origType: PType, name: Rope; info: TLineInfo) =
   cgsym(m, "TNimTypeV2")
   m.s[cfsStrData].addf("N_LIB_PRIVATE TNimTypeV2 $1;$n", [name])
@@ -1714,18 +1721,19 @@ proc genTypeInfoV2OldImpl(m: BModule; t, origType: PType, name: Rope; info: TLin
     m.s[cfsVars].addf("static $1 $2[$3] = $4;$n", [getTypeDesc(m, getSysType(m.g.graph, unknownLineInfo, tyUInt32), dkVar), objDisplayStore, rope(objDepth+1), objDisplay])
     addf(typeEntry, "$1.display = $2;$n", [name, rope(objDisplayStore)])
 
+  let dispatchMethods = toSeq(getMethodsPerType(m.g.graph, t))
+  if dispatchMethods.len > 0:
+    let vTablePointerName = getTempName(m)
+    m.s[cfsVars].addf("static void* $1[$2] = $3;$n", [vTablePointerName, rope(dispatchMethods.len), genVTable(dispatchMethods)])
+    for i in dispatchMethods:
+      genProcPrototype(m, i)
+    addf(typeEntry, "$1.vTable = $2;$n", [name, vTablePointerName])
+
   m.s[cfsTypeInit3].add typeEntry
 
   if t.kind == tyObject and t.len > 0 and t[0] != nil and optEnableDeepCopy in m.config.globalOptions:
     discard genTypeInfoV1(m, t, info)
 
-proc genVTable(seqs: seq[PSym]): string =
-  result = "{"
-  for i in 0..<seqs.len:
-    if i > 0: result.add ", "
-    result.add "(void *) " & seqs[i].loc.r
-  result.add "}"
-
 proc genTypeInfoV2Impl(m: BModule; t, origType: PType, name: Rope; info: TLineInfo) =
   cgsym(m, "TNimTypeV2")
   m.s[cfsStrData].addf("N_LIB_PRIVATE TNimTypeV2 $1;$n", [name])

compiler/cgen.nim

@@ -2234,8 +2234,7 @@ proc finalCodegenActions*(graph: ModuleGraph; m: BModule; n: PNode) =
         incl m.flags, objHasKidsValid
       if optMultiMethods in m.g.config.globalOptions or
           m.g.config.selectedGC notin {gcArc, gcOrc, gcAtomicArc} or
-          not m.g.config.isDefined("nimPreviewVtables") or
-          m.g.config.backend == backendCpp or sfCompileToCpp in m.module.flags:
+          not m.g.config.isDefined("nimPreviewVtables"):
         generateIfMethodDispatchers(graph, m.idgen)
 
 

compiler/sem.nim

@@ -842,9 +842,7 @@ proc semStmtAndGenerateGenerics(c: PContext, n: PNode): PNode =
   trackStmt(c, c.module, result, isTopLevel = true)
   if optMultiMethods notin c.config.globalOptions and
       c.config.selectedGC in {gcArc, gcOrc, gcAtomicArc} and
-      c.config.isDefined("nimPreviewVtables") and 
-      c.config.backend != backendCpp and
-      sfCompileToCpp notin c.module.flags:
+      c.config.isDefined("nimPreviewVtables"):
     sortVTableDispatchers(c.graph)
 
     if sfMainModule in c.module.flags:

lib/system.nim

@@ -1606,8 +1606,11 @@ when not defined(js) and defined(nimV2):
       traceImpl: pointer
       typeInfoV1: pointer # for backwards compat, usually nil
       flags: int
-      when defined(nimPreviewVtables) and not defined(cpp):
-        vTable: UncheckedArray[pointer] # vtable for types
+      when defined(nimPreviewVtables):
+        when defined(cpp):
+          vTable: ptr UncheckedArray[pointer] # vtable for types
+        else:
+          vTable: UncheckedArray[pointer] # vtable for types
     PNimTypeV2 = ptr TNimTypeV2
 
 proc supportsCopyMem(t: typedesc): bool {.magic: "TypeTrait".}

lib/system/arc.nim

@@ -244,7 +244,7 @@ template tearDownForeignThreadGc* =
 proc isObjDisplayCheck(source: PNimTypeV2, targetDepth: int16, token: uint32): bool {.compilerRtl, inl.} =
   result = targetDepth <= source.depth and source.display[targetDepth] == token
 
-when defined(nimPreviewVtables) and not defined(cpp):
+when defined(nimPreviewVtables):
   proc nimGetVTable(p: pointer, index: int): pointer
         {.compilerRtl, inline, raises: [].} =
     result = cast[ptr PNimTypeV2](p).vTable[index]

tests/method/tvtable.nim

@@ -1,3 +1,7 @@
+discard """
+  targets: "c cpp"
+"""
+
 type FooBase = ref object of RootObj
   dummy: int
 type Foo = ref object of FooBase
@@ -15,5 +19,6 @@ method bar(x: Foo2, a: float32)  =
 proc test() =
   var x = new Foo2
   x.bar(2.3)
+  doAssert x.value <= 2.3
 
 test()