1CMP0012 2------- 3 4:command:`if` recognizes numbers and boolean constants. 5 6In CMake versions 2.6.4 and lower the :command:`if` command implicitly 7dereferenced arguments corresponding to variables, even those named 8like numbers or boolean constants, except for ``0`` and ``1``. Numbers and 9boolean constants such as ``true``, ``false``, ``yes``, ``no``, ``on``, 10``off``, ``y``, ``n``, ``notfound``, ``ignore`` (all case insensitive) 11were recognized in some cases but not all. For example, the code ``if(TRUE)`` 12might have evaluated as ``false``. 13Numbers such as 2 were recognized only in boolean expressions 14like ``if(NOT 2)`` (leading to ``false``) but not as a single-argument like 15``if(2)`` (also leading to ``false``). Later versions of CMake prefer to 16treat numbers and boolean constants literally, so they should not be 17used as variable names. 18 19The ``OLD`` behavior for this policy is to implicitly dereference 20variables named like numbers and boolean constants. The ``NEW`` behavior 21for this policy is to recognize numbers and boolean constants without 22dereferencing variables with such names. 23 24This policy was introduced in CMake version 2.8.0. CMake version 25|release| warns when the policy is not set and uses ``OLD`` behavior. Use 26the :command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly. 27 28.. include:: DEPRECATED.txt 29