CMAKE_Fortran_PREPROCESS
From Get docs
Cmake/docs/3.21/variable/cmake fortran preprocess
CMAKE_Fortran_PREPROCESS
New in version 3.18.
Default value for Fortran_PREPROCESS of targets.
This variable is used to initialize the Fortran_PREPROCESS property on all the targets. See that target property for additional information.
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Licensed under the BSD 3-clause License.
https://cmake.org/cmake/help/v3.21/variable/CMAKE_Fortran_PREPROCESS.html