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CMP0012
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-------
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:command:`if` recognizes numbers and boolean constants.
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In CMake versions 2.6.4 and lower the :command:`if` command implicitly
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dereferenced arguments corresponding to variables, even those named
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like numbers or boolean constants, except for ``0`` and ``1``. Numbers and
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boolean constants such as ``true``, ``false``, ``yes``, ``no``, ``on``,
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``off``, ``y``, ``n``, ``notfound``, ``ignore`` (all case insensitive)
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were recognized in some cases but not all. For example, the code ``if(TRUE)``
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might have evaluated as ``false``.
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Numbers such as 2 were recognized only in boolean expressions
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like ``if(NOT 2)`` (leading to ``false``) but not as a single-argument like
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``if(2)`` (also leading to ``false``). Later versions of CMake prefer to
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treat numbers and boolean constants literally, so they should not be
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used as variable names.
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The ``OLD`` behavior for this policy is to implicitly dereference
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variables named like numbers and boolean constants. The ``NEW`` behavior
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for this policy is to recognize numbers and boolean constants without
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dereferencing variables with such names.
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This policy was introduced in CMake version 2.8.0. CMake version
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|release| warns when the policy is not set and uses ``OLD`` behavior. Use
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the :command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
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.. include:: DEPRECATED.txt
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