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| -rw-r--r-- | Help/policy/CMP0054.rst | 34 |
1 files changed, 31 insertions, 3 deletions
diff --git a/Help/policy/CMP0054.rst b/Help/policy/CMP0054.rst index dffee5e..39f0c40 100644 --- a/Help/policy/CMP0054.rst +++ b/Help/policy/CMP0054.rst @@ -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 |