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Compiler Options Macros

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These macros control specific compiler features.

Macro Description
_ATL_ALL_WARNINGS A symbol that enables errors in projects converted from previous versions of ATL.
_ATL_APARTMENT_THREADED Define if one or more of your objects use apartment threading.
_ATL_CSTRING_EXPLICIT_CONSTRUCTORS Makes certain CString constructors explicit, preventing any unintentional conversions.
_ATL_ENABLE_PTM_WARNING Define this macro to require C++ standard syntax. It generates the C4867 compiler error when nonstandard syntax is used to initialize a pointer to a member function.
_ATL_FREE_THREADED Define if one or more of your objects use free or neutral threading.
_ATL_MODULES Allows you to compile ATL projects with permissive- and use ATL with C++ modules.
_ATL_MULTI_THREADED A symbol that indicates the project has objects marked as Both, Free or Neutral. The macro _ATL_FREE_THREADED should be used instead.
_ATL_NO_AUTOMATIC_NAMESPACE A symbol that prevents the default use of namespace as ATL.
_ATL_NO_COM_SUPPORT A symbol that prevents COM-related code from being compiled with your project.
ATL_NO_VTABLE A symbol that prevents the vtable pointer from being initialized in the class's constructor and destructor.
ATL_NOINLINE A symbol that indicates a function shouldn't be inlined.
_ATL_SINGLE_THREADED Define if all of your objects use the single threading model.

_ATL_ALL_WARNINGS

A symbol that enables errors in projects converted from previous versions of ATL.

#define _ATL_ALL_WARNINGS

Remarks

Before Visual C++ .NET 2002, ATL disabled many warnings and left them disabled so that they never showed up in user code. Specifically:

  • C4127 conditional expression is constant

  • C4786 'identifier' : identifier was truncated to 'number' characters in the debug information

  • C4201 nonstandard extension used : nameless struct/union

  • C4103 'filename' : used #pragma pack to change alignment

  • C4291 'declaration' : no matching operator delete found; memory will not be freed if initialization throws an exception

  • C4268 'identifier' : 'const' static/global data initialized with compiler-generated default constructor fills the object with zeros

  • C4702 unreachable code

In projects converted from previous versions, these warnings are still disabled by the libraries headers.

To change this behavior, add the following line to the pch.h (stdafx.h in Visual Studio 2017 and earlier) file before including libraries headers.

#define _ATL_ALL_WARNINGS

If this #define is added, the ATL headers are careful to preserve the state of these warnings so that they're not disabled globally (or if the user explicitly disables individual warnings, not to enable them).

New projects have this #define set in pch.h (stdafx.h in Visual Studio 2017 and earlier) by default.

_ATL_APARTMENT_THREADED

Define if one or more of your objects use apartment threading.

_ATL_APARTMENT_THREADED

Remarks

Specifies apartment threading. For other options, and a description of the threading models available for an ATL object, see Specifying the Project's Threading Model and Options, ATL Simple Object Wizard.

_ATL_CSTRING_EXPLICIT_CONSTRUCTORS

Makes certain CString constructors explicit, preventing any unintentional conversions.

_ATL_CSTRING_EXPLICIT_CONSTRUCTORS

Remarks

When this constructor is defined, all CString constructors that take a single parameter are compiled with the explicit keyword, which prevents implicit conversions of input arguments. This means, for example, that when _UNICODE is defined, if you attempt to use a char* string as a CString constructor argument, a compiler error results. Use this macro in situations where you need to prevent implicit conversions between narrow and wide string types.

By using the _T macro on all constructor string arguments, you can define _ATL_CSTRING_EXPLICIT_CONSTRUCTORS and avoid compile errors regardless of whether _UNICODE is defined.

_ATL_ENABLE_PTM_WARNING

Define this macro in order to force the use of ANSI C++ standard-conforming syntax for pointer to member functions. Using this macro causes the C4867 compiler error to be generated when nonstandard syntax is used to initialize a pointer to a member function.

#define _ATL_ENABLE_PTM_WARNING

Remarks

The ATL and MFC libraries have been changed to match the Microsoft C++ compiler's improved standard C++ conformance. According to the ANSI C++ standard, the syntax of a pointer to a class member function should be &CMyClass::MyFunc.

When _ATL_ENABLE_PTM_WARNING isn't defined (the default case), ATL/MFC disables the C4867 error in macro maps (notably message maps) so that code that was created in earlier versions can continue to build as before. If you define _ATL_ENABLE_PTM_WARNING, your code should conform to the C++ standard.

However, the nonstandard form has been deprecated. You need to move existing code to C++ standard syntax. For example, the following code:

BEGIN_MESSAGE_MAP(CMFCListViewDoc, CDocument)
   ON_COMMAND(ID_MYCOMMAND, OnMycommand)
END_MESSAGE_MAP()

Should be changed to:

BEGIN_MESSAGE_MAP(CMFCListViewDoc, CDocument)
   ON_COMMAND(ID_MYCOMMAND, &CMFCListViewDoc::OnMycommand)
END_MESSAGE_MAP()

For map macros, add the ampersand '&' character. You shouldn't add the character again in your code.

_ATL_FREE_THREADED

Define if one or more of your objects use free or neutral threading.

_ATL_FREE_THREADED

Remarks

Specifies free threading. Free threading is equivalent to a multithread apartment model. See Specifying the Project's Threading Model for other threading options, and Options, ATL Simple Object Wizard for a description of the threading models available for an ATL object.

_ATL_MODULES

Allows you to compile ATL projects with permissive- and use ATL with C++ modules.

_ATL_MODULES

_ATL_MULTI_THREADED

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

_ATL_MULTI_THREADED

Remarks

If this symbol is defined, ATL pulls in code that will correctly synchronize access to global data. New code should use the equivalent macro _ATL_FREE_THREADED instead.

_ATL_NO_AUTOMATIC_NAMESPACE

A symbol that prevents the default use of namespace as ATL.

_ATL_NO_AUTOMATIC_NAMESPACE

Remarks

If this symbol isn't defined, including atlbase.h performs using namespace ATL by default, which may lead to naming conflicts. To prevent this, define this symbol.

_ATL_NO_COM_SUPPORT

A symbol that prevents COM-related code from being compiled with your project.

_ATL_NO_COM_SUPPORT

ATL_NO_VTABLE

A symbol that prevents the vtable pointer from being initialized in the class's constructor and destructor.

ATL_NO_VTABLE

Remarks

If the vtable pointer is prevented from being initialized in the class's constructor and destructor, the linker can eliminate the vtable and all of the functions to which it points. Expands to __declspec(novtable).

Example

class ATL_NO_VTABLE CMyClass2 :

ATL_NOINLINE

A symbol that indicates a function shouldn't be inlined.

    ATL_NOINLINE inline
    myfunction()
    {
    ...
    }

Parameters

myfunction
The function that shouldn't be inlined.

Remarks

Use this symbol if you want to ensure a function doesn't get inlined by the compiler, even though it must be declared as inline so that it can be placed in a header file. Expands to __declspec(noinline).

_ATL_SINGLE_THREADED

Define if all of your objects use the single threading model

_ATL_SINGLE_THREADED

Remarks

Specifies that the object always runs in the primary COM thread. See Specifying the Project's Threading Model for other threading options, and Options, ATL Simple Object Wizard for a description of the threading models available for an ATL object.

See also

Macros