Commit 0c349e1

description: "Learn more about: Compiler Options Macros"

title: "Compiler Options Macros"

ms.date: "08/19/2019"

helpviewer_keywords: ["compiler options, macros"]

ms.assetid: a869adc6-b3de-4299-b040-9ae20b45f82c

|[_ATL_CSTRING_EXPLICIT_CONSTRUCTORS](#_atl_cstring_explicit_constructors)|Makes certain `CString` constructors explicit, preventing any unintentional conversions.|

|[_ATL_ENABLE_PTM_WARNING](#_atl_enable_ptm_warning)|Define this macro to require C++ standard syntax. It generates the C4867 compiler error when non-standard syntax is used to initialize a pointer to a member function.|

|[_ATL_FREE_THREADED](#_atl_free_threaded)|Define if one or more of your objects use free or neutral threading.|

|[_ATL_MULTI_THREADED](#_atl_multi_threaded)|A symbol that indicates the project will have objects that are marked as Both, Free or Neutral. The macro [_ATL_FREE_THREADED](#_atl_free_threaded) should be used instead.|

|[_ATL_NO_AUTOMATIC_NAMESPACE](#_atl_no_automatic_namespace)|A symbol that prevents the default use of namespace as ATL.|

|[_ATL_NO_COM_SUPPORT](#_atl_no_com_support)|A symbol that prevents COM-related code from being compiled with your project.|

Specifies free threading. Free threading is equivalent to a multithread apartment model. See [Specifying the Project's Threading Model](../../atl/specifying-the-threading-model-for-a-project-atl.md) for other threading options, and [Options, ATL Simple Object Wizard](../../atl/reference/options-atl-simple-object-wizard.md) for a description of the threading models available for an ATL object.

A symbol that indicates the project will have objects that are marked as Both, Free or Neutral.