Better dependency management for Cereal (#740)

* Better dependency management

Without this, KaMPIng does not work in conjuction with code which also
depends on cereal.

This requires us to bump to minimum required CMake version to
3.24 (shipped by all major distributions/easy to install).

This first tries to find a system installed cereal, and otherwise
fetches it via FetchContent and builds from source.

This also provides an option to completely disable serialization,
thereby getting rid of the dependency.

More dependency/CMake cleanup will be part of another PR.

* Just install cereal.

* Remove old debug output.

* Add `SYSTEM` keyword to `FetchContent_Declare` and bump CMake to 3.25.

.gitmodules

@@ -10,9 +10,6 @@
 [submodule "extern/pfr"]
 	path = extern/pfr
 	url = https://github.com/apolukhin/pfr_non_boost
-[submodule "extern/cereal"]
-	path = extern/cereal
-	url = https://github.com/USCiLab/cereal
 [submodule "cmake/Format.cmake"]
 	path = cmake/Format.cmake
 	url = https://github.com/TheLartians/Format.cmake

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.12)
+cmake_minimum_required(VERSION 3.25)
 
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_LIST_DIR}/cmake")
 
@@ -7,10 +7,11 @@ project(
     kamping
     DESCRIPTION "An MPI wrapper which makes using MPI feel like C++"
     LANGUAGES CXX
-    VERSION 0.1.0
+    VERSION 0.1.1
 )
+include(FetchContent)
 
-if (CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
+if (PROJECT_IS_TOP_LEVEL)
     # folder support for IDEs
     set_property(GLOBAL PROPERTY USE_FOLDERS ON)
 
@@ -56,9 +57,10 @@ option(KAMPING_WARNINGS_ARE_ERRORS OFF)
 option(KAMPING_BUILD_EXAMPLES_AND_TESTS OFF)
 option(KAMPING_TESTS_DISCOVER OFF)
 option(KAMPING_ENABLE_ULFM "Enable User-Level Failure-Mitigation (ULFM)" OFF)
+option(KAMPING_ENABLE_SERIALIZATION "Enable support for serialization (requires Cereal)" ON)
 
 # Enable compilation with ccache. Defaults to ON if this is the main project.
-if (CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME)
+if (PROJECT_IS_TOP_LEVEL)
     option(KAMPING_USE_CCACHE "Globally enable ccache." ON)
 else ()
     option(KAMPING_USE_CCACHE "Globally enable ccache." OFF)
@@ -203,17 +205,32 @@ add_library(pfr INTERFACE)
 target_include_directories(pfr SYSTEM INTERFACE extern/pfr/include)
 target_link_libraries(kamping_base INTERFACE pfr)
 
-add_library(cereal INTERFACE)
-add_library(cereal::cereal ALIAS cereal)
-target_include_directories(cereal SYSTEM INTERFACE extern/cereal/include)
-target_compile_features(cereal INTERFACE cxx_std_11)
-target_link_libraries(kamping_base INTERFACE cereal)
+if (KAMPING_ENABLE_SERIALIZATION)
+    FetchContent_Declare(
+        cereal
+        GIT_REPOSITORY https://github.com/USCiLab/cereal
+        GIT_TAG v1.3.2
+        SYSTEM FIND_PACKAGE_ARGS NAMES cereal 1.3.2
+    )
+    set(JUST_INSTALL_CEREAL ON)
+    FetchContent_MakeAvailable(cereal)
+    if (cereal_FOUND)
+        message(STATUS "Found cereal: ${cereal_DIR}")
+    else ()
+        message(STATUS "Cereal: building from source.")
+    endif ()
+    target_link_libraries(kamping_base INTERFACE cereal::cereal)
+    message(STATUS "Serialization: enabled")
+else ()
+    target_compile_definitions(kamping_base INTERFACE KAMPING_DISABLE_SERIALIZATION)
+    message(STATUS "Serialization: disabled")
+endif ()
 
 add_library(kamping::kamping ALIAS kamping)
 
 # Testing and examples are only built if this is the main project or if KAMPING_BUILD_EXAMPLES_AND_TESTS is set (OFF by
 # default)
-if (CMAKE_PROJECT_NAME STREQUAL PROJECT_NAME OR KAMPING_BUILD_EXAMPLES_AND_TESTS)
+if (PROJECT_IS_TOP_LEVEL OR KAMPING_BUILD_EXAMPLES_AND_TESTS)
     add_subdirectory(examples)
     add_subdirectory(tests)
 endif ()

examples/usage/CMakeLists.txt

@@ -50,6 +50,8 @@ add_executable(example_datatype datatype_example.cpp)
 target_link_libraries(example_datatype kamping)
 target_compile_options(example_datatype PRIVATE ${KAMPING_WARNING_FLAGS})
 
-add_executable(example_serialization serialization_example.cpp)
-target_link_libraries(example_serialization kamping cereal::cereal)
-target_compile_options(example_serialization PRIVATE ${KAMPING_WARNING_FLAGS})
+if (KAMPING_ENABLE_SERIALIZATION)
+    add_executable(example_serialization serialization_example.cpp)
+    target_link_libraries(example_serialization kamping cereal::cereal)
+    target_compile_options(example_serialization PRIVATE ${KAMPING_WARNING_FLAGS})
+endif ()

examples/usage/allgatherv_example.cpp

@@ -18,8 +18,6 @@
 #include <kamping/serialization.hpp>
 #include <mpi.h>
 
-#include "cereal/types/string.hpp"
-#include "cereal/types/unordered_map.hpp"
 #include "helpers_for_examples.hpp"
 #include "kamping/checking_casts.hpp"
 #include "kamping/collectives/allgather.hpp"

include/kamping/serialization.hpp

@@ -17,11 +17,14 @@
 
 #include <type_traits>
 
-#include "cereal/archives/binary.hpp"
+#if !defined(KAMPING_DISABLE_SERIALIZATION)
+    #include "cereal/archives/binary.hpp"
+#endif
 #include "kamping/data_buffer.hpp"
 
 namespace kamping {
 namespace internal {
+#if !defined(KAMPING_DISABLE_SERIALIZATION)
 
 /// @brief Buffer holding serialized data.
 ///
@@ -92,17 +95,19 @@ class SerializationBuffer {
         return _data.size();
     }
 };
+#endif
 
 /// @brief Tag type to identify serialization support.
 struct serialization_support_tag {};
 
 /// @brief Type trait to check if a type is a serialization buffer.
 template <typename>
 constexpr bool is_serialization_buffer_v_impl = false;
-
+#if !defined(KAMPING_DISABLE_SERIALIZATION)
 /// @brief Type trait to check if a type is a serialization buffer.
 template <typename... Args>
 constexpr bool is_serialization_buffer_v_impl<SerializationBuffer<Args...>> = true;
+#endif
 
 /// @brief Type trait to check if a type is a serialization buffer.
 template <typename T>
@@ -123,7 +128,7 @@ auto deserialization_repack(BufferType buffer) {
     }
 }
 } // namespace internal
-
+#if !defined(KAMPING_DISABLE_SERIALIZATION)
 /// @brief Serializes an object using [`cereal`](https://uscilab.github.io/cereal/).
 /// @tparam Archive Type of the archive to use for serialization (see
 /// https://uscilab.github.io/cereal/serialization_archives.html). Default is `cereal::BinaryOutputArchive`.
@@ -235,5 +240,6 @@ auto as_deserializable(T&& object) {
         return internal::SerializationBuffer<void, Archive, Allocator, decltype(buffer)>(std::move(buffer));
     }
 }
+#endif
 
 } // namespace kamping

tests/CMakeLists.txt

@@ -288,11 +288,13 @@ kamping_register_mpi_test(
     FILES helpers_for_testing_mpi_test.cpp
     CORES 1 4
 )
-kamping_register_mpi_test(
-    test_serialization
-    FILES serialization_test.cpp
-    CORES 1 2 4
-)
+if (KAMPING_ENABLE_SERIALIZATION)
+    kamping_register_mpi_test(
+        test_serialization
+        FILES serialization_test.cpp
+        CORES 1 2 4
+    )
+endif ()
 kamping_register_mpi_test(
     test_flatten
     FILES utils/flatten_test.cpp