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53 lines
2.2 KiB
ReStructuredText
53 lines
2.2 KiB
ReStructuredText
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CMP0053
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-------
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.. versionadded:: 3.1
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Simplify variable reference and escape sequence evaluation.
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CMake 3.1 introduced a much faster implementation of evaluation of the
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:ref:`Variable References` and :ref:`Escape Sequences` documented in the
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:manual:`cmake-language(7)` manual. While the behavior is identical
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to the legacy implementation in most cases, some corner cases were
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cleaned up to simplify the behavior. Specifically:
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* Expansion of ``@VAR@`` reference syntax defined by the
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:command:`configure_file` and :command:`string(CONFIGURE)`
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commands is no longer performed in other contexts.
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* Literal ``${VAR}`` reference syntax may contain only
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alphanumeric characters (``A-Z``, ``a-z``, ``0-9``) and
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the characters ``_``, ``.``, ``/``, ``-``, and ``+``.
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Note that ``$`` is technically allowed in the ``NEW`` behavior, but is
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invalid for ``OLD`` behavior. This is due to an oversight during the
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implementation of ``CMP0053`` and its use as a literal variable
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reference is discouraged for this reason.
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Variables with other characters in their name may still
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be referenced indirectly, e.g.
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.. code-block:: cmake
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set(varname "otherwise & disallowed $ characters")
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message("${${varname}}")
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* The setting of policy :policy:`CMP0010` is not considered,
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so improper variable reference syntax is always an error.
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* More characters are allowed to be escaped in variable names.
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Previously, only ``()#" \@^`` were valid characters to
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escape. Now any non-alphanumeric, non-semicolon, non-NUL
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character may be escaped following the ``escape_identity``
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production in the :ref:`Escape Sequences` section of the
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:manual:`cmake-language(7)` manual.
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The ``OLD`` behavior for this policy is to honor the legacy behavior for
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variable references and escape sequences. The ``NEW`` behavior is to
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use the simpler variable expansion and escape sequence evaluation rules.
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This policy was introduced in CMake version 3.1.
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CMake version |release| warns when the policy is not set and uses
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``OLD`` behavior. Use the :command:`cmake_policy` command to set
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it to ``OLD`` or ``NEW`` explicitly.
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.. include:: DEPRECATED.txt
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