From 597b60019bdc4dd9ebb4b09215503cbff6988a10 Mon Sep 17 00:00:00 2001
From: Sebastian Beyer <sebastian.beyer@awi.de>
Date: Sun, 3 May 2026 21:00:49 +0200
Subject: [PATCH] build: integrate CVMix via FetchContent instead of download
 script

Replace the custom download_cvmix.sh + add_custom_command + IMPORTED-target
plumbing with FetchContent_MakeAvailable. CVMix is now built as a regular
CMake subproject inside the build tree (no source-tree pollution, no separate
sub-cmake invocation).

For builds on internet-restricted machines, point at a manually placed
checkout with -DFETCHCONTENT_SOURCE_DIR_CVMIX=/path/to/CVMix-src and pass
-DFETCHCONTENT_FULLY_DISCONNECTED=ON.
---
 .gitignore                         |   3 +-
 src/CMakeLists.txt                 |  81 +++++++----------------
 src/cvmix_driver/download_cvmix.sh | 100 -----------------------------
 3 files changed, 24 insertions(+), 160 deletions(-)
 delete mode 100644 src/cvmix_driver/download_cvmix.sh

diff --git a/.gitignore b/.gitignore
index 4a6e7bc68..c7f681645 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,6 +14,5 @@ lib/*.so
 /work_*
 Makefile.in
 mesh_part/build
-test/output_pi 
-src/cvmix_driver/CVMix-*
+test/output_pi
 .claude/
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index e400cf295..8753d398e 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -199,65 +199,30 @@ target_include_directories(${PROJECT_NAME} PUBLIC $<BUILD_INTERFACE:${CMAKE_Fort
 target_include_directories(${PROJECT_NAME} PUBLIC $<INSTALL_INTERFACE:module/fesom>)
 target_link_libraries(${PROJECT_NAME} PRIVATE MPI::MPI_Fortran)
 
-# build CVMix library if CVMIX is ON
-if (CVMIX)
+# Pull CVMix in via FetchContent and build it as part of FESOM's build tree.
+# Offline workflow:
+#   - point at a manually placed checkout: -DFETCHCONTENT_SOURCE_DIR_CVMIX=/path/to/CVMix-src
+#   - or pre-populate <build>/_deps/cvmix-src and pass -DFETCHCONTENT_FULLY_DISCONNECTED=ON
+if(CVMIX)
    message(STATUS "CVMIX: ${CVMIX}")
-   
-   # read CVMix install and src directories from the download script, so that there
-   # is only one place where they are defined
-   execute_process(COMMAND bash ${src_home}/cvmix_driver/download_cvmix.sh --print-src_dir
-                   OUTPUT_VARIABLE CVMIX_DIR_src OUTPUT_STRIP_TRAILING_WHITESPACE)
-   execute_process(COMMAND bash ${src_home}/cvmix_driver/download_cvmix.sh --print-prefix
-                   OUTPUT_VARIABLE CVMIX_DIR_install OUTPUT_STRIP_TRAILING_WHITESPACE)  
-   
-   # set default CVMix installation path
-   set(CVMIX_ROOT "${src_home}/cvmix_driver/${CVMIX_DIR_install}_${CMAKE_Fortran_COMPILER_ID}") 
-   message(STATUS "set default CVMIX_ROOT=${CVMIX_ROOT}")
-   
-   # Where library is located --> fix in download_cvmix.sh that it as always installed 
-   # in /lib and not in /lib64
-   set(CVMIX_LIB "${CVMIX_ROOT}/lib/libcvmix.a")
-   
-   # Create parent directory early so CMake does not fail on missing include paths
-   file(MAKE_DIRECTORY ${CVMIX_ROOT})
-   file(MAKE_DIRECTORY ${CVMIX_ROOT}/include/cvmix)
-   
-   # Collect CVMix source files so that CMake knows what changes triggers a 
-   # possible rebuild of the CVMix library
-   file(GLOB_RECURSE CVMIX_SOURCES
-         "${src_home}/cvmix_driver/${CVMIX_DIR_src}/src/*.F90"
-         "${src_home}/cvmix_driver/${CVMIX_DIR_src}/src/*/*.F90")
-        
-   # Add script dependency (rebuild if script changes)
-   set(CVMIX_DOWNLOAD "${src_home}/cvmix_driver/download_cvmix.sh")
-   
-   # Custom command: build CVMix if not yet built
-   add_custom_command(
-         OUTPUT ${CVMIX_LIB}
-         COMMAND bash ${src_home}/cvmix_driver/download_cvmix.sh --prefix ${CVMIX_ROOT}
-         WORKING_DIRECTORY ${src_home}/cvmix_driver
-         DEPENDS ${CVMIX_SOURCES} ${CVMIX_DOWNLOAD} # trigger rebuild if source or download script change
-         COMMENT "Downloading and building CVMix into ${CVMIX_ROOT}"
-         VERBATIM)
-   
-   # check if ${CVMIX_ROOT}/lib/libcvmix.a exist or not, only if it does not 
-   # exist build library
-   add_custom_target(cvmix_autobuild DEPENDS ${CVMIX_LIB})
- 
-   # build cvmix external libray
-   add_library(cvmix_external STATIC IMPORTED GLOBAL)
-   set_target_properties(cvmix_external PROPERTIES
-         IMPORTED_LOCATION ${CVMIX_LIB}
-         INTERFACE_INCLUDE_DIRECTORIES "${CVMIX_ROOT}/include/cvmix")
-
-   # cvmix_autobuild is a custom target that runs your download_cvmix.sh script 
-   # and produces libcvmix.a. cvmix_external is an imported library, meaning CMake 
-   # doesn’t build it — it just points to an existing file (libcvmix.a).
-   add_dependencies(cvmix_external  cvmix_autobuild)
-   
-   # Link CVMix library to fesom, build chain becomes: fesom → cvmix_external → cvmix_autobuild
-   target_link_libraries(${PROJECT_NAME} PRIVATE cvmix_external)
-   
+
+   include(FetchContent)
+   set(CVMIX_BUILD_SHARED_LIBS OFF CACHE BOOL "" FORCE)
+   set(CVMIX_BUILD_DRIVER      OFF CACHE BOOL "" FORCE)
+   FetchContent_Declare(cvmix
+      GIT_REPOSITORY https://github.com/CVMix/CVMix-src.git
+      GIT_TAG        v1.0.0
+   )
+   FetchContent_MakeAvailable(cvmix)
+
+   # CVMix's own CMakeLists exposes its module dir only via INSTALL_INTERFACE and
+   # writes .mod files to ${CMAKE_BINARY_DIR}/modules (top-level build dir, set
+   # in the subdirectory scope). Expose that path on the BUILD_INTERFACE so
+   # FESOM's wrapper sources in cvmix_driver/ can find the CVMix .mod files.
+   target_include_directories(cvmix_static INTERFACE
+      $<BUILD_INTERFACE:${CMAKE_BINARY_DIR}/modules>)
+
+   target_link_libraries(${PROJECT_NAME} PRIVATE cvmix_static)
 endif()
 
 set_target_properties(${PROJECT_NAME} PROPERTIES LINKER_LANGUAGE Fortran)
diff --git a/src/cvmix_driver/download_cvmix.sh b/src/cvmix_driver/download_cvmix.sh
deleted file mode 100644
index 4d126297c..000000000
--- a/src/cvmix_driver/download_cvmix.sh
+++ /dev/null
@@ -1,100 +0,0 @@
-#!/usr/bin/env bash
-set -euo pipefail
-
-# Clone and build CVMix-src locally for FESOM2
-# Usage:
-#   ./get_cvmix.sh [--branch <branch_or_tag>] [--prefix <install_prefix>]
-# Defaults:
-#   branch: master
-#   prefix: $(pwd)/CVMix-install
-# Result:
-#   Installs CVMix to <prefix>, producing:
-#     <prefix>/lib/libcvmix.a
-#     <prefix>/include/*.mod
-#
-# Then configure FESOM with CMake options:
-#   -DUSE_EXTERNAL_CVMIX=ON \
-#   -DCVMIX_ROOT=<prefix>
-# or
-#   -DCVMIX_LIB_DIR=<prefix>/lib -DCVMIX_MOD_DIR=<prefix>/include
-REPO_URL="https://github.com/CVMix/CVMix-src.git"
-BRANCH="" #"master"
-TAG="v1.0.0"
-PREFIX="CVMix-install"
-SRC_DIR="CVMix-src"
-BUILD_DIR="CVMix-build"
-
-# to extract the proper src and install dir for cmake, so the are always 
-# synchronized with the download script
-[[ "${1:-}" == "--print-prefix" ]] && {
-  echo "$PREFIX"
-  exit 0
-}
-[[ "${1:-}" == "--print-src_dir" ]] && {
-  echo "$PREFIX"
-  exit 0
-}
-[[ "${1:-}" == "--print-build_dir" ]] && {
-  echo "$PREFIX"
-  exit 0
-}
-PREFIX=$(pwd)/${PREFIX}
-SRC_DIR=$(pwd)/${SRC_DIR}
-BUILD_DIR=$(pwd)/${BUILD_DIR}
-
-
-while [[ $# -gt 0 ]]; do
-  case "$1" in
-    --branch)
-      BRANCH="$2"; TAG=""; shift 2;;
-    --tag)
-      TAG="$2"; BRANCH=""; shift 2;;
-    --prefix)
-      PREFIX="$2"; shift 2;;
-    *) echo "Unknown arg: $1"; exit 1;;
-  esac
-done
-
-mkdir -p "$(dirname "$PREFIX")"
-
-if [[ ! -d "$SRC_DIR/.git" ]]; then
-  if [[ -n "$TAG" ]]; then
-    echo "Cloning CVMix-src at tag $TAG ..."
-    git clone --branch "$TAG" --depth 1 "$REPO_URL" "$SRC_DIR"
-  else
-    echo "Cloning CVMix-src at branch $BRANCH ..."
-    git clone --branch "$BRANCH" --depth 1 "$REPO_URL" "$SRC_DIR"
-  fi  
-else
-  echo "Updating existing CVMix-src ..."  
-  
-  if [[ -n "$TAG" ]]; then
-    git -C "$SRC_DIR" fetch --tags
-    git -C "$SRC_DIR" checkout -q "tags/$TAG"
-  else
-    git -C "$SRC_DIR" fetch --depth 1 origin "$BRANCH" 
-    git -C "$SRC_DIR" checkout -q "$BRANCH" 
-    git -C "$SRC_DIR" reset --hard "origin/$BRANCH"
-  fi
-fi
-
-rm -rf "$BUILD_DIR"
-mkdir -p "$BUILD_DIR"
-
-cd "$BUILD_DIR"
-cmake -DCMAKE_BUILD_TYPE=Release \
-      -DCMAKE_Fortran_MODULE_DIRECTORY="$PREFIX/include" \
-      -DCMAKE_INSTALL_PREFIX="$PREFIX" \
-      -DCMAKE_INSTALL_LIBDIR=lib \
-      "$SRC_DIR"
-
-cmake --build . --config Release -- -j
-cmake --install .
-
-echo
-echo "CVMix installed to: $PREFIX"
-echo "  lib: $PREFIX/lib"
-echo "  mods: $PREFIX/include"
-echo
-echo "Configure FESOM CMake with:"
-echo "  -DUSE_EXTERNAL_CVMIX=ON -DCVMIX_ROOT=$PREFIX"