CMake/Help/policy/CMP0098.rst

CMP0098
-------

:module:`FindFLEX` runs ``flex`` in directory
:variable:`CMAKE_CURRENT_BINARY_DIR` when executing.

The module provides a ``FLEX_TARGET`` macro which generates FLEX output.
In CMake 3.16 and below the macro would generate a custom command that runs
``flex`` in the current source directory.  CMake 3.17 and later prefer to
run it in the build directory and use :variable:`CMAKE_CURRENT_BINARY_DIR`
as the ``WORKING_DIRECTORY`` of its :command:`add_custom_command` invocation.
This ensures that any implicitly generated file is written relative to the
build tree rather than the source tree, unless the generated file is
provided as absolute path.

This policy provides compatibility for projects that have not been updated
to expect the new behavior.

The ``OLD`` behavior for this policy is for ``FLEX_TARGET`` to use
the current source directory for the ``WORKING_DIRECTORY`` and where
to generate implicit files. The ``NEW`` behavior of this policy is to
use the current binary directory for the ``WORKING_DIRECTORY`` relative to
which implicit files are generated unless provided as absolute path.

This policy was introduced in CMake version 3.17.  Use the
:command:`cmake_policy` command to set it to ``OLD`` or ``NEW`` explicitly.
Unlike many policies, CMake version |release| does *not* warn
when this policy is not set and simply uses ``OLD`` behavior.

.. include:: DEPRECATED.txt