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51 lines
1.5 KiB
51 lines
1.5 KiB
CMP0124
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-------
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.. versionadded:: 3.21
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:command:`foreach` loop variables are only available in the loop scope.
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CMake 3.20 and below always leave the loop variable set at the end of the
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loop, either to the value it had before the loop, if any, or to the empty
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string. CMake 3.21 and above prefer to leave the loop variable in the
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state it had before the loop started, either set or unset. This policy
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provides compatibility for projects that expect the loop variable to always
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be left set.
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The ``OLD`` behavior for this policy is to set the loop variable at the
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end of the loop, either to its original value, or to an empty value.
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The ``NEW`` behavior for this policy is to restore the loop variable to
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the state it had before the loop started, either set or unset.
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For example:
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.. code-block:: cmake
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set(items a b c)
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set(var1 "value")
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unset(var2)
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foreach(var1 IN LISTS items)
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endforeach()
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foreach(var2 IN LISTS items)
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endforeach()
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if(DEFINED var1)
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message("var1: ${var1}")
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endif()
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if(DEFINED var2)
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message("var2: ${var2}")
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endif()
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Under the ``OLD`` behavior, this code prints ``var1: value`` and ``var2:``.
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Under the ``NEW`` behavior, this code prints only ``var1: value``.
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This policy was introduced in CMake version 3.21. Use the
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:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
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Unlike many policies, CMake version |release| does *not* warn when the policy
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is not set and simply uses ``OLD`` behavior.
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.. include:: DEPRECATED.txt
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