Add VERSION_VAR to find_package_handle_standard_args to handle FFTW version

.github/workflows/test.yml

@@ -24,6 +24,24 @@ jobs:
           cmake -S test -B build \
             -DFFTW_TEST_COMPONENTS="${fftw_components}"
 
+      - name: Configure test with version 3
+        run: |
+          cmake -S test -B build \
+            -DFFTW_TEST_COMPONENTS="${fftw_components}" \
+            -DFFTW_TEST_VERSION=3
+
+      - name: Configure test with invalid version
+        run: |
+          set +e
+          cmake -S test -B build_version_fail -DFFTW_TEST_VERSION=999.99.9 2>/dev/null
+          STATUS=$?
+          if [ $STATUS -ne 0 ]; then
+            echo "PASS: find_package correctly rejected version 999.99.9"
+          else
+            echo "FAIL: find_package should have rejected version 999.99.9 but succeeded"
+            exit 1
+          fi
+
   test-source:
     name: Test source install
     runs-on: ubuntu-latest
@@ -79,6 +97,13 @@ jobs:
             -DFFTW_ROOT="$HOME/fftw_install" \
             -DFFTW_TEST_COMPONENTS="${fftw_components}"
 
+      - name: Configure test with version 3
+        run: |
+          cmake -S test -B build \
+            -DFFTW_ROOT="$HOME/fftw_install" \
+            -DFFTW_TEST_COMPONENTS="${fftw_components}" \
+            -DFFTW_TEST_VERSION=3
+
   test-conda:
     name: Test conda-forge install
     runs-on: ubuntu-latest
@@ -99,3 +124,11 @@ jobs:
           cmake -S test -B build \
             -DFFTW_ROOT="$CONDA_PREFIX" \
             -DFFTW_TEST_COMPONENTS="${fftw_components}"
+
+      - name: Configure test with version 3
+        shell: micromamba-shell {0}
+        run: |
+          cmake -S test -B build \
+            -DFFTW_ROOT="$CONDA_PREFIX" \
+            -DFFTW_TEST_COMPONENTS="${fftw_components}" \
+            -DFFTW_TEST_VERSION=3

FindFFTW.cmake

@@ -7,14 +7,15 @@
 #   Copyright (c) 2017, Patrick Bos
 #
 # Usage:
-#   find_package(FFTW [REQUIRED] [QUIET] [COMPONENTS component1 ... componentX] )
+#   find_package(FFTW [<version>] [REQUIRED] [QUIET] [COMPONENTS component1 ... componentX] )
 #
 # It sets the following variables:
 #   FFTW_FOUND                  ... true if fftw is found on the system
 #   FFTW_[component]_LIB_FOUND  ... true if the component is found on the system (see components below)
 #   FFTW_LIBRARIES              ... full paths to all found fftw libraries
 #   FFTW_[component]_LIB        ... full path to one of the components (see below)
 #   FFTW_INCLUDE_DIRS           ... fftw include directory paths
+#   FFTW_VERSION                ... version of the found fftw library
 #
 # The following variables will be checked by the function
 #   FFTW_USE_STATIC_LIBS        ... if true, only static libraries are found, otherwise both static and shared.
@@ -44,9 +45,31 @@ endif()
 # Check if we can use PkgConfig
 find_package(PkgConfig)
 
-#Determine from PKG
+# Determine from PKG
 if( PKG_CONFIG_FOUND AND NOT FFTW_ROOT )
     pkg_check_modules( PKG_FFTW QUIET "fftw3" )
+    set( FFTW_VERSION ${PKG_FFTW_VERSION} )
+else()
+    # If pkg-config was skipped, there seems no way to get the version directly.
+    # Try to deduce the version from fftw-wisdom-to-conf instead.
+    #   (From @kprussing. See https://github.com/egpbos/findFFTW/pull/8)
+    execute_process(COMMAND ${FFTW_ROOT}/bin/fftw-wisdom-to-conf -V
+                    RESULT_VARIABLE _fftw_wtc_success
+                    OUTPUT_VARIABLE _fftw_wtc_stdout
+                    ERROR_VARIABLE _fftw_wtc_stderr)
+    if (_fftw_wtc_success EQUAL 0)
+        string(REGEX MATCH "FFTW *version *([0-9]+([.][0-9]+([.][0-9]+)?)?)"
+                _fftw_wtc_version ${_fftw_wtc_stdout})
+        string(REPLACE " " ";" _fftw_wtc_version_list ${_fftw_wtc_version})
+        list(GET _fftw_wtc_version_list -1 FFTW_VERSION)
+    else()
+        message(WARNING "Error running ${FFTW_ROOT}/bin/fftw-wisdom-to-conf. "
+                        "Could not determine FFTW version.
+Output:
+${_fftw_wtc_stdout}
+Error:
+${_fftw_wtc_stderr}")
+    endif()
 endif()
 
 #Check whether to search static or dynamic libs
@@ -398,6 +421,7 @@ include(FindPackageHandleStandardArgs)
 
 find_package_handle_standard_args(FFTW
     REQUIRED_VARS FFTW_INCLUDE_DIRS
+    VERSION_VAR FFTW_VERSION
     HANDLE_COMPONENTS
     )
 

README.md

@@ -5,7 +5,7 @@ CMake module for finding FFTW 3 using find_package
 Once added to your project, this module allows you to find FFTW libraries and headers using the CMake `find_package` command:
 
 ```cmake
-find_package(FFTW [REQUIRED] [QUIET] [COMPONENTS component1 ... componentX] )
+find_package(FFTW [<version>] [REQUIRED] [QUIET] [COMPONENTS component1 ... componentX] )
 ```
 
 This module sets the following variables:
@@ -14,6 +14,7 @@ This module sets the following variables:
 - `FFTW_LIBRARIES`              ... full paths to all found fftw libraries
 - `FFTW_[component]_LIB`        ... full path to one of the components (see below)
 - `FFTW_INCLUDE_DIRS`           ... fftw include directory paths
+- `FFTW_VERSION`                ... version of the found fftw library
 
 The following variables will be checked by the module:
 - `FFTW_USE_STATIC_LIBS`        ... if true, only static libraries are found, otherwise both static and shared.

test/CMakeLists.txt

@@ -6,10 +6,10 @@ list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/..")
 
 # Find FFTW. If FFTW_TEST_COMPONENTS is given (semicolon-separated list), those
 # components are required; otherwise we just require that FFTW itself is found.
-if(DEFINED FFTW_TEST_COMPONENTS)
-    find_package(FFTW REQUIRED COMPONENTS ${FFTW_TEST_COMPONENTS})
+if(FFTW_TEST_COMPONENTS)
+    find_package(FFTW ${FFTW_TEST_VERSION} REQUIRED COMPONENTS ${FFTW_TEST_COMPONENTS})
 else()
-    find_package(FFTW REQUIRED)
+    find_package(FFTW ${FFTW_TEST_VERSION} REQUIRED)
 endif()
 
 # ---------------------------------------------------------------------------
@@ -27,6 +27,20 @@ if(NOT FFTW_LIBRARIES)
     message(FATAL_ERROR "FFTW_LIBRARIES is empty after find_package(FFTW REQUIRED)")
 endif()
 
+if(NOT FFTW_VERSION)
+    message(FATAL_ERROR "FFTW_VERSION is empty after find_package(FFTW REQUIRED)")
+endif()
+
+# ---------------------------------------------------------------------------
+# Version checks
+# ---------------------------------------------------------------------------
+if(FFTW_TEST_VERSION)
+    if(NOT "${FFTW_VERSION}" VERSION_GREATER_EQUAL "${FFTW_TEST_VERSION}")
+        message(FATAL_ERROR
+            "Expected FFTW_VERSION >= ${FFTW_TEST_VERSION} but got ${FFTW_VERSION}")
+    endif()
+endif()
+
 # ---------------------------------------------------------------------------
 # Map component names to their CMake imported target names
 # ---------------------------------------------------------------------------
@@ -71,6 +85,7 @@ endforeach()
 # ---------------------------------------------------------------------------
 message(STATUS "FindFFTW test passed!")
 message(STATUS "  FFTW_FOUND:        ${FFTW_FOUND}")
+message(STATUS "  FFTW_VERSION:      ${FFTW_VERSION}")
 message(STATUS "  FFTW_INCLUDE_DIRS: ${FFTW_INCLUDE_DIRS}")
 message(STATUS "  FFTW_LIBRARIES:    ${FFTW_LIBRARIES}")