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Every policy's documentation has a paragraph on what version of CMake introduced it, how to set the policy, and whether CMake warns if the policy is not set. The wording of this paragraph has diverged across policies over time. Factor the paragraph out into a standard advice document included by every policy.
50 lines
1.4 KiB
ReStructuredText
50 lines
1.4 KiB
ReStructuredText
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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.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.21
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.. |WARNS_OR_DOES_NOT_WARN| replace:: does *not* warn
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.. include:: STANDARD_ADVICE.txt
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.. include:: DEPRECATED.txt
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