Active Template Library
| Developer(s) | Microsoft |
|---|---|
| Development status | Current |
| Written in | C++ |
| Operating system | Microsoft Windows |
| Type | Library or framework |
| License | Proprietary |
The Active Template Library (ATL) is a set of template-based C++ classes developed by Microsoft, intended to simplify the programming of Component Object Model (COM) objects. The COM support in Microsoft Visual C++ allows developers to create a variety of COM objects, OLE Automation servers, and ActiveX controls.[1][2] ATL includes an object wizard that sets up primary structure of the objects very quickly with a minimum of hand coding. On the COM client side ATL provides smart pointers that deal with COM reference counting.
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History [edit]
COM objects can also be created with Microsoft Foundation Classes (MFC), but this leads to larger binaries that require support DLLs.[3] ATL, on the other hand, is a more lightweight alternative in situations where the graphical user interface parts of MFC are not required.[4]
In ATL version 7 (Visual Studio 2003), which directly succeeded version 3 (Visual Studio 6.0), a number of MFC classes like CString were made available in ATL, or more precisely moved to an ATLMFC common layer which is shared by both libraries. ATL version 7 also introduced attributes in C++ in an attempt to provide something similar to CLI attributes, however these have not been particularly successful, and have been deemphasized in ATL version 8 (Visual Studio 2005); the various wizards no longer generate them by default. Version 7 also introduced new string conversion classes.
On July 28, 2009, Microsoft released a patch to ATL to fix a bug that could allow ActiveX controls created using ATL to be vulnerable to a remote code execution security flaw.[5]
Support classes [edit]
ATL includes many RAII classes to simplify management of COM types. The most commonly used classes include:
CComPtr<T>[6] general-purpose smart-pointer,CComBSTR[7] BSTR wrapper,CComVariant[8] VARIANT wrapper, andCComSafeArray<T>[9] SAFEARRAY wrapper.
Compiler COM support [edit]
Allthough not formally part of ATL, Microsoft Visual C++ also includes additional C++ RAII classes to simplify management of COM types. These compiler COM support classes can be used as replacement for or in combination with ATL, and includes:
_com_ptr_t[10] smart-pointer that decorates the COM interface name with a "Ptr" suffix,_bstr_t[11] BSTR wrapper,_variant_t[12] VARIANT wrapper, and_com_error[13] HRESULT wrapper.
Note that as of Visual Studio 2012, the compiler COM support classes does not include a SAFEARRAY wrapper.
See also [edit]
References [edit]
- ^ Grimes, Richard (1998). "ATL and COM". ATL COM (1st edition ed.). Wrox Press. p. 6. ISBN 1-86100-249-1.
- ^ Grimes, Richard (1999). "Building and calling a COM object using ATL". Beginning ATL 3 COM Programming (1st edition ed.). Wrox Press. p. 63. ISBN 978-1-86100-120-7.
- ^ Williams, Mickey (2000). "Active Documents". Visual C++ 6 Unleashed (1st edition ed.). Sams. p. 733. ISBN 978-0-672-31241-0.
- ^ Microsoft MSDN: Recommendations for Choosing Between ATL and MFC
- ^ "ATL Security Update". MSDN. Microsoft. 2009-07-28. Retrieved 2011-09-19.
- ^ Microsoft MSDN: CComPtr Class
- ^ Microsoft MSDN: CComBSTR Class
- ^ Microsoft MSDN: CComVariant Class
- ^ Microsoft MSDN: CComSafeArray Class
- ^ Microsoft MSDN: _com_ptr_t Class
- ^ Microsoft MSDN: _bstr_t Class
- ^ Microsoft MSDN: _variant_t Class
- ^ Microsoft MSDN: _com_error Class
External links [edit]
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