ad3c2c0b03
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.
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2.8 KiB
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94 lines
2.8 KiB
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CMP0069
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-------
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.. versionadded:: 3.9
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:prop_tgt:`INTERPROCEDURAL_OPTIMIZATION` is enforced when enabled.
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CMake 3.9 and newer prefer to add IPO flags whenever the
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:prop_tgt:`INTERPROCEDURAL_OPTIMIZATION` target property is enabled and
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produce an error if flags are not known to CMake for the current compiler.
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Since a given compiler may not support IPO flags in all environments in which
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it is used, it is now the project's responsibility to use the
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:module:`CheckIPOSupported` module to check for support before enabling the
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:prop_tgt:`INTERPROCEDURAL_OPTIMIZATION` target property. This approach
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allows a project to conditionally activate IPO when supported. It also
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allows an end user to set the :variable:`CMAKE_INTERPROCEDURAL_OPTIMIZATION`
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variable in an environment known to support IPO even if the project does
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not enable the property.
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Since CMake 3.8 and lower only honored :prop_tgt:`INTERPROCEDURAL_OPTIMIZATION`
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for the Intel compiler on Linux, some projects may unconditionally enable the
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target property. Policy ``CMP0069`` provides compatibility with such projects.
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This policy takes effect whenever the IPO property is enabled. The ``OLD``
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behavior for this policy is to add IPO flags only for Intel compiler on Linux.
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The ``NEW`` behavior for this policy is to add IPO flags for the current
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compiler or produce an error if CMake does not know the flags.
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.. |INTRODUCED_IN_CMAKE_VERSION| replace:: 3.9
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.. |WARNS_OR_DOES_NOT_WARN| replace:: warns
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.. include:: STANDARD_ADVICE.txt
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.. include:: DEPRECATED.txt
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Examples
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^^^^^^^^
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Behave like CMake 3.8 and do not apply any IPO flags except for Intel compiler
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on Linux:
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.. code-block:: cmake
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cmake_minimum_required(VERSION 3.8)
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project(foo)
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# ...
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set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
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Use the :module:`CheckIPOSupported` module to detect whether IPO is
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supported by the current compiler, environment, and CMake version.
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Produce a fatal error if support is not available:
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.. code-block:: cmake
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cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
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project(foo)
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include(CheckIPOSupported)
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check_ipo_supported()
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# ...
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set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
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Apply IPO flags only if compiler supports it:
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.. code-block:: cmake
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cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
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project(foo)
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include(CheckIPOSupported)
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# ...
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check_ipo_supported(RESULT result)
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if(result)
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set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
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endif()
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Apply IPO flags without any checks. This may lead to build errors if IPO
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is not supported by the compiler in the current environment. Produce an
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error if CMake does not know IPO flags for the current compiler:
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.. code-block:: cmake
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cmake_minimum_required(VERSION 3.9) # CMP0069 NEW
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project(foo)
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# ...
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set_property(TARGET ... PROPERTY INTERPROCEDURAL_OPTIMIZATION TRUE)
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