don't trust completeStruct for typeinfo gen of imported C++ types

fixes nim-lang#24159, refs nim-lang#23761

compiler/ccgtypes.nim

@@ -1474,7 +1474,10 @@ proc genObjectInfo(m: BModule; typ, origType: PType, name: Rope; info: TLineInfo
                       typeToString(typ))
   genTypeInfoAux(m, typ, origType, name, info)
   var tmp = getNimNode(m)
-  if (not isImportedType(typ)) or tfCompleteStruct in typ.flags:
+  if (not isImportedType(typ)) or
+      # don't trust C++ imported fields even if completeStruct to
+      # workaround C++ atomic implementation
+      (tfCompleteStruct in typ.flags and not isImportedCppType(typ)):
     genObjectFields(m, typ, origType, typ.n, tmp, info)
   m.s[cfsTypeInit3].addf("$1.node = &$2;$n", [tiNameForHcr(m, name), tmp])
   var t = typ.baseClass

tests/ccgbugs/tatomictypeinfo.nim

@@ -0,0 +1,14 @@
+discard """
+  matrix: "--mm:refc; --mm:orc"
+  targets: "c cpp"
+"""
+
+# issue #24159 
+
+import std/atomics
+
+type N = object
+  u: ptr Atomic[int]
+proc w(args: N) = discard
+var e: Thread[N]
+createThread(e, w, default(N))

tests/ccgbugs/tcgbug.nim

@@ -4,6 +4,7 @@ success
 M1 M2
 ok
 '''
+targets: "c cpp"
 matrix: "--mm:refc;--mm:orc"
 """