build: move library sources under lib/ for subtree split

Move the library sources (CMakeLists.txt, cmake/, include/, pkgconfig/,
src/, test/) under a single lib/ prefix so that

    git subtree split --prefix=lib -b lib

produces a 'lib' branch containing only the files needed for a full
library build and install. Downstream projects consuming libmultiprocess
as a git subtree can pull from this branch and avoid churn from changes
to CI scripts, README, doc/, examples, shell.nix and other files that
are not part of the library itself.

A new top-level CMakeLists.txt wrapper preserves 'cmake -S .' for
standalone builds; this is also the only way to build the example/
subdirectory, which lives outside lib/ since downstream subtree
consumers do not need it. See comments in CMakeLists.txt and
lib/CMakeLists.txt for details on how lib/ adapts between the two
build modes.

The bulk of this commit is a pure file move (renames only). Outside
the move itself, only minimal touch-ups were necessary in
lib/CMakeLists.txt and ci/scripts/{ci,bitcoin_core_ci}.sh.

Author: Sjors

CMakeLists.txt

@@ -2,263 +2,30 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
+# Top-level wrapper for standalone builds (`cmake -S .`). Adds the example
+# subdirectory, which is the only thing not relevant to subtree consumers
+# (which configure `lib/` directly via `add_subdirectory()`).
+#
+# The actual library, generator, headers, tests and pkg-config template live
+# under `lib/` so that `git subtree split --prefix=lib` produces a `lib`
+# branch suitable for use as a slim git subtree by downstream projects.
+
 cmake_minimum_required(VERSION 3.12)
 
 project("Libmultiprocess" CXX)
-if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
-  set(CMAKE_CXX_STANDARD 20)
-  set(CMAKE_CXX_STANDARD_REQUIRED YES)
-endif()
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED YES)
 
-include("cmake/compat_find.cmake")
+# Tell lib/CMakeLists.txt that this is a standalone build, even though it is
+# being processed via add_subdirectory() rather than as the top-level source.
+set(MP_STANDALONE TRUE)
+include(CTest)
 
+# Threads::Threads and Cap'n Proto targets are needed by the example/
+# subdirectory. find_package() creates IMPORTED targets in the calling
+# directory's scope, so do it here as well as in lib/CMakeLists.txt.
 find_package(Threads REQUIRED)
 find_package(CapnProto 0.7 QUIET NO_MODULE)
- if(NOT CapnProto_FOUND)
-   message(FATAL_ERROR
-     "Cap'n Proto is required but was not found.\n"
-     "To resolve, choose one of the following:\n"
-     "  - Install Cap'n Proto (version 1.0+ recommended)\n"
-     "  - For Bitcoin Core compilation build with -DENABLE_IPC=OFF to disable multiprocess support\n"
-   )
- endif()
-
-# Cap'n Proto compatibility checks
-set(CAPNPROTO_ISSUES "")
-set(CAPNPROTO_CVE_AFFECTED FALSE)
-set(CAPNPROTO_CLANG_INCOMPATIBLE FALSE)
-
-# Check for list-of-pointers memory access bug from Nov 2022
-# https://nvd.nist.gov/vuln/detail/CVE-2022-46149
-# https://github.com/advisories/GHSA-qqff-4vw4-f6hx
-# https://github.com/capnproto/capnproto/security/advisories/GHSA-qqff-4vw4-f6hx
-# https://github.com/capnproto/capnproto/blob/master/security-advisories/2022-11-30-0-pointer-list-bounds.md
-# https://capnproto.org/news/2022-11-30-CVE-2022-46149-security-advisory.html
-# https://dwrensha.github.io/capnproto-rust/2022/11/30/out_of_bounds_memory_access_bug.html
-if(CapnProto_VERSION STREQUAL "0.7.0"
-   OR CapnProto_VERSION STREQUAL "0.8.0"
-   OR CapnProto_VERSION STREQUAL "0.9.0"
-   OR CapnProto_VERSION STREQUAL "0.9.1"
-   OR CapnProto_VERSION STREQUAL "0.10.0"
-   OR CapnProto_VERSION STREQUAL "0.10.1"
-   OR CapnProto_VERSION STREQUAL "0.10.2")
-  set(CAPNPROTO_CVE_AFFECTED TRUE)
-  string(APPEND CAPNPROTO_ISSUES "- CVE-2022-46149 security vulnerability (details: https://github.com/advisories/GHSA-qqff-4vw4-f6hx)\n")
-endif()
-
-# Check for Cap'n Proto / Clang / C++20 incompatibility
-# Cap'n Proto 0.9.x and 0.10.x are incompatible with Clang 16+ when using C++20
-# due to P2468R2 implementation. This was fixed in Cap'n Proto 1.0+.
-# See: https://github.com/bitcoin-core/libmultiprocess/issues/199
-if((CapnProto_VERSION VERSION_GREATER_EQUAL "0.9.0") AND
-   (CapnProto_VERSION VERSION_LESS "1.0.0") AND
-   (CMAKE_CXX_COMPILER_ID STREQUAL "Clang") AND
-   (CMAKE_CXX_COMPILER_VERSION VERSION_GREATER_EQUAL "16") AND
-   (CMAKE_CXX_STANDARD EQUAL 20))
-  set(CAPNPROTO_CLANG_INCOMPATIBLE TRUE)
-  string(APPEND CAPNPROTO_ISSUES "- Incompatible with Clang ${CMAKE_CXX_COMPILER_VERSION} when using C++20\n")
-endif()
-
-if(CAPNPROTO_CVE_AFFECTED OR CAPNPROTO_CLANG_INCOMPATIBLE)
-  set(RESOLUTION_OPTIONS "")
-
-  # Fixes both issues
-  string(APPEND RESOLUTION_OPTIONS "  - Upgrade to Cap'n Proto version 1.0 or newer (recommended)\n")
-
-  if(CAPNPROTO_CVE_AFFECTED AND NOT CAPNPROTO_CLANG_INCOMPATIBLE)
-    string(APPEND RESOLUTION_OPTIONS "  - Upgrade to a patched minor version (0.7.1, 0.8.1, 0.9.2, 0.10.3, or later)\n")
-  elseif(CAPNPROTO_CLANG_INCOMPATIBLE AND NOT CAPNPROTO_CVE_AFFECTED)
-    string(APPEND RESOLUTION_OPTIONS "  - Use GCC instead of Clang\n")
-  endif()
-
-  string(APPEND RESOLUTION_OPTIONS "  - For Bitcoin Core compilation build with -DENABLE_IPC=OFF to disable multiprocess support\n")
-
-  message(FATAL_ERROR
-    "The version of Cap'n Proto detected: ${CapnProto_VERSION} has known compatibility issues:\n"
-    "${CAPNPROTO_ISSUES}"
-    "To resolve, choose one of the following:\n"
-    "${RESOLUTION_OPTIONS}"
-  )
-endif()
-
-set(MPGEN_EXECUTABLE "" CACHE FILEPATH "If specified, should be full path to an external mpgen binary to use rather than the one built internally.")
-
-option(MP_ENABLE_CLANG_TIDY "Run clang-tidy with the compiler." OFF)
-if(MP_ENABLE_CLANG_TIDY)
-  find_program(CLANG_TIDY_EXECUTABLE NAMES clang-tidy)
-  if(NOT CLANG_TIDY_EXECUTABLE)
-    message(FATAL_ERROR "MP_ENABLE_CLANG_TIDY is ON but clang-tidy is not found.")
-  endif()
-  set(CMAKE_CXX_CLANG_TIDY "${CLANG_TIDY_EXECUTABLE}")
-
-  # Workaround for nix from https://gitlab.kitware.com/cmake/cmake/-/issues/20912#note_793338
-  # Nix injects header paths via $NIX_CFLAGS_COMPILE; CMake tags these as
-  # CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES and omits them from the compile
-  # database, so clang-tidy, which ignores $NIX_CFLAGS_COMPILE, can't find capnp
-  # headers. Setting them as standard passes them to clang-tidy.
-  set(CMAKE_CXX_STANDARD_INCLUDE_DIRECTORIES ${CMAKE_CXX_IMPLICIT_INCLUDE_DIRECTORIES})
-endif()
-
-option(MP_ENABLE_IWYU "Run include-what-you-use with the compiler." OFF)
-if(MP_ENABLE_IWYU)
-  find_program(IWYU_EXECUTABLE NAMES include-what-you-use iwyu)
-  if(NOT IWYU_EXECUTABLE)
-    message(FATAL_ERROR "MP_ENABLE_IWYU is ON but include-what-you-use was not found.")
-  endif()
-  set(CMAKE_CXX_INCLUDE_WHAT_YOU_USE "${IWYU_EXECUTABLE};-Xiwyu;--error")
-  if(DEFINED ENV{IWYU_MAPPING_FILE})
-    list(APPEND CMAKE_CXX_INCLUDE_WHAT_YOU_USE "-Xiwyu" "--mapping_file=$ENV{IWYU_MAPPING_FILE}")
-  endif()
-endif()
-
-include("cmake/compat_config.cmake")
-include("cmake/pthread_checks.cmake")
-include(GNUInstallDirs)
-
-# Set MP_INCLUDE_DIR as a global property so target_capnp_sources function can
-# use it, and its callers don't need to specify the include directory manually
-# to avoid "error: Import failed: /mp/proxy.capnp" failures from capnproto.
-set_property(GLOBAL PROPERTY MP_INCLUDE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/include")
-
-# Set a convenience variable for subdirectories.
-if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
-  set(MP_STANDALONE TRUE)
-  include(CTest)
-else()
-  set(MP_STANDALONE FALSE)
-endif()
-
-# Prevent include directories from parent project from leaking into this one.
-set_property(DIRECTORY PROPERTY INCLUDE_DIRECTORIES "")
-
-# Generated C++ preprocessor defines
-configure_file(include/mp/config.h.in "${CMAKE_CURRENT_BINARY_DIR}/include/mp/config.h")
-
-# Generated C++ Capn'Proto schema files
-capnp_generate_cpp(MP_PROXY_SRCS MP_PROXY_HDRS include/mp/proxy.capnp)
-set_source_files_properties("${MP_PROXY_SRCS}" PROPERTIES SKIP_LINTING TRUE) # Ignored before cmake 3.27
-
-# util library
-add_library(mputil OBJECT src/mp/util.cpp)
-target_include_directories(mputil PRIVATE
-  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-  $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>)
-target_link_libraries(mputil PUBLIC CapnProto::kj)
-
-# libmultiprocess.a runtime library
-set(MP_PUBLIC_HEADERS
-  ${MP_PROXY_HDRS}
-  include/mp/proxy-io.h
-  include/mp/proxy-types.h
-  include/mp/proxy.h
-  include/mp/type-char.h
-  include/mp/type-chrono.h
-  include/mp/type-context.h
-  include/mp/type-data.h
-  include/mp/type-decay.h
-  include/mp/type-exception.h
-  include/mp/type-function.h
-  include/mp/type-interface.h
-  include/mp/type-map.h
-  include/mp/type-message.h
-  include/mp/type-number.h
-  include/mp/type-optional.h
-  include/mp/type-pair.h
-  include/mp/type-pointer.h
-  include/mp/type-set.h
-  include/mp/type-string.h
-  include/mp/type-struct.h
-  include/mp/type-threadmap.h
-  include/mp/type-tuple.h
-  include/mp/type-vector.h
-  include/mp/type-void.h
-  include/mp/util.h)
-add_library(multiprocess STATIC
-  ${MP_PROXY_SRCS}
-  ${MP_PUBLIC_HEADERS}
-  src/mp/proxy.cpp
-  $<TARGET_OBJECTS:mputil>)
-add_library(Libmultiprocess::multiprocess ALIAS multiprocess)
-target_include_directories(multiprocess PUBLIC
-  $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>
-  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
-  $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
-target_link_libraries(multiprocess PUBLIC CapnProto::capnp)
-target_link_libraries(multiprocess PUBLIC CapnProto::capnp-rpc)
-target_link_libraries(multiprocess PUBLIC CapnProto::kj)
-target_link_libraries(multiprocess PUBLIC CapnProto::kj-async)
-set_target_properties(multiprocess PROPERTIES
-    PUBLIC_HEADER "${MP_PUBLIC_HEADERS}")
-install(TARGETS multiprocess EXPORT LibTargets
-  ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR} COMPONENT lib
-  PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/mp COMPONENT lib)
-
-# mpgen code generator
-add_executable(mpgen src/mp/gen.cpp $<TARGET_OBJECTS:mputil>)
-add_executable(Libmultiprocess::mpgen ALIAS mpgen)
-target_include_directories(mpgen PRIVATE $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>)
-target_include_directories(mpgen PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include> $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>)
-target_link_libraries(mpgen PRIVATE CapnProto::capnp)
-target_link_libraries(mpgen PRIVATE CapnProto::capnp-rpc)
-target_link_libraries(mpgen PRIVATE CapnProto::capnpc)
-target_link_libraries(mpgen PRIVATE CapnProto::kj)
-target_link_libraries(mpgen PRIVATE Threads::Threads)
-set_target_properties(mpgen PROPERTIES
-    INSTALL_RPATH_USE_LINK_PATH TRUE)
-set_target_properties(mpgen PROPERTIES
-    PUBLIC_HEADER include/mp/proxy.capnp)
-install(TARGETS mpgen EXPORT BinTargets
-  RUNTIME DESTINATION ${CMAKE_INSTALL_BINDIR} COMPONENT bin
-  PUBLIC_HEADER DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}/mp COMPONENT bin)
-
-# makefile include to invoke mpgen code generator, for downstream Make projects
-install(FILES "include/mpgen.mk"
-  DESTINATION ${CMAKE_INSTALL_INCLUDEDIR} COMPONENT bin)
-
-# pkg-config module to build against libmultiprocess library, for downstream autoconf projects
-configure_file(pkgconfig/libmultiprocess.pc.in "${CMAKE_CURRENT_BINARY_DIR}/pkgconfig/libmultiprocess.pc" @ONLY)
-install(FILES "${CMAKE_CURRENT_BINARY_DIR}/pkgconfig/libmultiprocess.pc"
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig COMPONENT lib)
-
-# cmake include to invoke mpgen code generator, for downstream CMake projects
-install(
-  FILES
-    ${CMAKE_CURRENT_SOURCE_DIR}/cmake/TargetCapnpSources.cmake
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess COMPONENT bin)
-
-# CMake target import files, for downstream CMake projects
-install(EXPORT BinTargets
-  NAMESPACE Libmultiprocess::
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess COMPONENT bin)
-install(EXPORT LibTargets
-  NAMESPACE Libmultiprocess::
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess COMPONENT lib)
-
-# CMake find_package config file, for downstream CMake projects
-include(CMakePackageConfigHelpers)
-configure_package_config_file(
-  ${PROJECT_SOURCE_DIR}/cmake/Config.cmake.in
-  LibmultiprocessConfig.cmake
-  INSTALL_DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess
-  NO_SET_AND_CHECK_MACRO)
-install(
-  FILES
-    ${CMAKE_CURRENT_BINARY_DIR}/LibmultiprocessConfig.cmake
-  DESTINATION ${CMAKE_INSTALL_LIBDIR}/cmake/Libmultiprocess
-  COMPONENT common)
-
-# Makefile targets to support "make install-bin" "make install-lib"
-add_custom_target(install-bin
-  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=bin -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
-  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=common -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
-  VERBATIM)
-add_dependencies(install-bin mpgen)
-add_custom_target(install-lib
-  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=lib -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
-  COMMAND ${CMAKE_COMMAND} -DCOMPONENT=common -P ${CMAKE_CURRENT_BINARY_DIR}/cmake_install.cmake
-  VERBATIM)
-add_dependencies(install-lib multiprocess)
 
-# Example and test subdirectories
+add_subdirectory(lib)
 add_subdirectory(example EXCLUDE_FROM_ALL)
-add_subdirectory(test EXCLUDE_FROM_ALL)

ci/scripts/bitcoin_core_ci.sh

@@ -10,8 +10,10 @@ source "${SCRIPT_DIR}/ci_helpers.sh"
 
 replace_subtree() {
   rm -rf src/ipc/libmultiprocess
-  cp -a _libmultiprocess src/ipc/libmultiprocess
-  rm -rf src/ipc/libmultiprocess/.git
+  # The Bitcoin Core subtree mirrors the contents of the upstream 'lib'
+  # branch, which is 'git subtree split --prefix=lib' of master. Replace the
+  # subtree with the same lib/ contents the split branch would publish.
+  cp -a _libmultiprocess/lib src/ipc/libmultiprocess
 }
 
 add_llvm_apt_repository() {

ci/scripts/ci.sh

@@ -21,6 +21,12 @@ cmake --version
 cmake_ver=$(cmake --version | awk '/version/{print $3; exit}')
 ver_ge() { [ "$(printf '%s\n' "$2" "$1" | sort -V | head -n1)" = "$2" ]; }
 
+# The library sources live under lib/ so that 'git subtree split --prefix=lib'
+# produces a 'lib' branch suitable for consumption as a git subtree by
+# downstream projects, without pulling in CI scripts, examples, pkg-config
+# templates, documentation or other upstream-only files. Standalone builds use
+# the top-level CMakeLists.txt wrapper, which adds the example/ subdirectory
+# and pkg-config install rules on top of lib/.
 src_dir=$PWD
 mkdir -p "$CI_DIR"
 cd "$CI_DIR"

example/CMakeLists.txt

@@ -2,8 +2,6 @@
 # Distributed under the MIT software license, see the accompanying
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-include(${PROJECT_SOURCE_DIR}/cmake/TargetCapnpSources.cmake)
-
 add_executable(mpcalculator
   calculator.cpp
 )