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Help: Extend policy CMP0054 documentation with an example

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Nils Gladitz 2014-12-09 21:52:23 +01:00 committed by Brad King
parent 1f6f114a7a
commit f2f1c95dd9
1 changed files with 31 additions and 3 deletions
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Help/policy/CMP0054.rst
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@ -3,15 +3,43 @@ CMP0054
Only interpret :command:`if` arguments as variables or keywords when unquoted.
CMake 3.1 and above no longer dereference variables or interpret keywords
in an :command:`if` command argument when it is a :ref:`Quoted Argument`
or a :ref:`Bracket Argument`.
CMake 3.1 and above no longer implicitly dereference variables or
interpret keywords in an :command:`if` command argument when
it is a :ref:`Quoted Argument` or a :ref:`Bracket Argument`.
The ``OLD`` behavior for this policy is to dereference variables and
interpret keywords even if they are quoted or bracketed.
The ``NEW`` behavior is to not dereference variables or interpret keywords
that have been quoted or bracketed.
Given the following partial example:
::
set(MONKEY 1)
set(ANIMAL MONKEY)
if("${ANIMAL}" STREQUAL "MONKEY")
After explicit expansion of variables this gives:
::
if("MONKEY" STREQUAL "MONKEY")
With the policy set to ``OLD`` implicit expansion reduces this semantically to:
::
if("1" STREQUAL "1")
With the policy set to ``NEW`` the quoted arguments will not be
further dereferenced:
::
if("MONKEY" STREQUAL "MONKEY")
This policy was introduced in CMake version 3.1.
CMake version |release| warns when the policy is not set and uses
``OLD`` behavior. Use the :command:`cmake_policy` command to set