[Code scan] Do not require fftw3f when ENABLE_FLOAT_FFTW is off

[njzjz]

This issue is a result of a Codex global repository scan.

ENABLE_FLOAT_FFTW defaults to OFF, and the top-level build only links FFTW3::FFTW3_FLOAT when that option is enabled. However, FindFFTW3.cmake always searches for fftw3f and includes FFTW3_FLOAT_LIBRARY in find_package_handle_standard_args(), so double-precision-only FFTW installations can fail configure even when single-precision FFTW support is disabled.

Option and top-level link condition:

abacus-develop/CMakeLists.txt

Lines 23 to 25 in 84ca04b

	option(USE_ABACUS_LIBM "Build libmath from source to speed up" OFF)
	option(ENABLE_LIBXC "Enable using the LibXC package" OFF)
	option(ENABLE_FLOAT_FFTW "Enable using single-precision FFTW library." OFF)

abacus-develop/CMakeLists.txt

Lines 630 to 646 in 84ca04b

	find_package(FFTW3 REQUIRED)
	find_package(Lapack REQUIRED)
	include_directories(${FFTW3_INCLUDE_DIRS})
	list(APPEND math_libs FFTW3::FFTW3 LAPACK::LAPACK BLAS::BLAS)
	# ScaLAPACK is a distributed-memory library and is only needed for the
	# MPI build. A serial build (e.g. the native Windows serial version)
	# must not require it.
	if(ENABLE_MPI)
	find_package(ScaLAPACK REQUIRED)
	list(APPEND math_libs ScaLAPACK::ScaLAPACK)
	endif()
	if(USE_OPENMP)
	list(APPEND math_libs FFTW3::FFTW3_OMP)
	endif()
	if(ENABLE_FLOAT_FFTW)
	list(APPEND math_libs FFTW3::FFTW3_FLOAT)
	endif()

Find module requirement:

abacus-develop/cmake/FindFFTW3.cmake

Lines 19 to 40 in 84ca04b

	find_library(FFTW3_FLOAT_LIBRARY
	NAMES fftw3f
	HINTS ${FFTW3_DIR}
	PATH_SUFFIXES "lib"
	)
	# both libfftw3.so and libfftw3_omp.so should be link in multi-thread term
	if (USE_OPENMP)
	find_library(FFTW3_OMP_LIBRARY
	NAMES fftw3_omp
	HINTS ${FFTW3_DIR}
	PATH_SUFFIXES "lib"
	)
	endif()
	# Handle the QUIET and REQUIRED arguments and
	# set FFTW3_FOUND to TRUE if all variables are non-zero.
	include(FindPackageHandleStandardArgs)
	if (USE_OPENMP)
	find_package_handle_standard_args(FFTW3 DEFAULT_MSG FFTW3_OMP_LIBRARY FFTW3_LIBRARY FFTW3_FLOAT_LIBRARY FFTW3_INCLUDE_DIR)
	else()
	find_package_handle_standard_args(FFTW3 DEFAULT_MSG FFTW3_LIBRARY FFTW3_FLOAT_LIBRARY FFTW3_INCLUDE_DIR)

Relevant code:

find_library(FFTW3_FLOAT_LIBRARY NAMES fftw3f ...)
...
find_package_handle_standard_args(FFTW3 DEFAULT_MSG FFTW3_LIBRARY FFTW3_FLOAT_LIBRARY FFTW3_INCLUDE_DIR)

Suggested fix:

Only search for and require FFTW3_FLOAT_LIBRARY when ENABLE_FLOAT_FFTW is enabled. Keep the imported FFTW3::FFTW3_FLOAT target conditional on that option as well.