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- include_guard
- -------------
- Provides an include guard for the file currently being processed by CMake.
- ::
- include_guard([DIRECTORY|GLOBAL])
- Sets up an include guard for the current CMake file (see the
- :variable:`CMAKE_CURRENT_LIST_FILE` variable documentation).
- CMake will end its processing of the current file at the location of the
- :command:`include_guard` command if the current file has already been
- processed for the applicable scope (see below). This provides functionality
- similar to the include guards commonly used in source headers or to the
- ``#pragma once`` directive. If the current file has been processed previously
- for the applicable scope, the effect is as though :command:`return` had been
- called. Do not call this command from inside a function being defined within
- the current file.
- An optional argument specifying the scope of the guard may be provided.
- Possible values for the option are:
- ``DIRECTORY``
- The include guard applies within the current directory and below. The file
- will only be included once within this directory scope, but may be included
- again by other files outside of this directory (i.e. a parent directory or
- another directory not pulled in by :command:`add_subdirectory` or
- :command:`include` from the current file or its children).
- ``GLOBAL``
- The include guard applies globally to the whole build. The current file
- will only be included once regardless of the scope.
- If no arguments given, ``include_guard`` has the same scope as a variable,
- meaning that the include guard effect is isolated by the most recent
- function scope or current directory if no inner function scopes exist.
- In this case the command behavior is the same as:
- .. code-block:: cmake
- if(__CURRENT_FILE_VAR__)
- return()
- endif()
- set(__CURRENT_FILE_VAR__ TRUE)
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