Dynamic-Link Libraries and IPC

It is possible to build a Win32-based dynamic-link library (DLL) so that its global data is shared with all processes that call the DLL. Therefore, cooperating processes can call the DLL to examine and modify global data owned by the DLL. For example, process A calls a DLL function with data that the DLL stores in its global data space. Process B calls another DLL function that retrieves that data. Because of the multitasking nature of the Win32 API, the DLL would have to use a semaphore or another synchronization object to control access to the shared memory.

Although shared global data can be used in a DLL, Win32 file mapping is recommended for shared memory. File mapping is more efficient and provides the additional benefit of access protection. (For example, a client can be limited to read-only access to a file-mapping object.)

Key Point Although a developer can use shared global data segments in a DLL to allow two or more applications to share data, it is preferable to use Win32 file-mapping functions to create shared memory. For more information, see Dynamic-Link Libraries.

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