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CMake

# =============================================================================
# Dependencies.cmake
#
# Three ways to bring in a third-party dependency, and one helper that ties
# two of them together. All three keep the dependency's own warnings out of
# your build (SYSTEM) and its sources out of compile_commands.json, so
# clangd/clang-tidy stay focused on code this project owns.
#
# add_vendor_header_only(NAME [INCLUDE_DIR <dir>])
# A buildless (header-only) drop checked into vendor/<NAME>/include
# (or vendor/<INCLUDE_DIR>). Wraps it as an INTERFACE target NAME.
#
# add_vendor_subdirectory(SUBDIR)
# A vendored dependency that ships its own CMakeLists.txt, checked
# into vendor/<SUBDIR> (a plain source drop, git submodule, or git
# subtree). Whatever target names that CMakeLists.txt defines are
# what you DEPENDS on.
#
# add_dependency(NAME <FetchContent_Declare args...>)
# CMake's native find_package + FetchContent integration: pass
# FIND_PACKAGE_ARGS ... to try an already-installed copy (an apt/
# vcpkg/conan package) first, and only download + build from source
# if nothing is found. Omit FIND_PACKAGE_ARGS to always fetch.
# https://cmake.org/cmake/help/latest/module/FetchContent.html#integrating-with-find-package
#
# All three are safe to call more than once for the same name (e.g. two
# modules that both need the same dependency) -- later calls are no-ops.
#
# A module DEPENDS on whatever target the chosen path defines, exactly
# like depending on another module -- add_lib_module/add_exe_module don't
# need to know or care which of the three supplied it.
#
# IMPORTANT -- installing: a vendored/fetched dependency's own
# CMakeLists.txt usually has its own install() rules, and there is no
# reliable, version-independent way to suppress them from here (EXCLUDE_
# FROM_ALL's effect on install() is explicitly documented as undefined,
# and CMAKE_SKIP_INSTALL_RULES breaks `cmake --install` outright for
# FetchContent -- both were tried and rejected). The actual fix lives in
# CMakeLists.txt: our own install(TARGETS ...) calls are tagged
# COMPONENT ${PROJECT_CODE_NAME}, and scripts/install.sh / install.bat always pass
# --component so a third-party dependency's untagged install rules are
# never pulled in. Installing with plain `cmake --install build` (no
# --component) will also install whatever the dependency wanted to
# install, typically under CMAKE_INSTALL_PREFIX (e.g. /usr/local) --
# use the install script, or pass --component yourself.
# =============================================================================
include_guard(GLOBAL)
# -----------------------------------------------------------------------
# _exclude_from_compile_commands(DIR): drop every target defined under
# DIR from compile_commands.json. Applied to vendored/fetched third-party
# code so the exported compile database stays focused on code this
# project actually owns.
# -----------------------------------------------------------------------
function(_exclude_from_compile_commands DIR)
if(NOT IS_DIRECTORY "${DIR}")
return()
endif()
get_property(_pmn_dir_targets DIRECTORY "${DIR}" PROPERTY BUILDSYSTEM_TARGETS)
foreach(_t ${_pmn_dir_targets})
set_target_properties(${_t} PROPERTIES EXPORT_COMPILE_COMMANDS OFF)
endforeach()
endfunction()
# -----------------------------------------------------------------------
# add_vendor_header_only(NAME [INCLUDE_DIR <dir>])
# -----------------------------------------------------------------------
macro(add_vendor_header_only NAME)
cmake_parse_arguments(ARG "" "INCLUDE_DIR" "" ${ARGN})
if(NOT TARGET ${NAME})
add_library(${NAME} INTERFACE)
if(ARG_INCLUDE_DIR)
target_include_directories(${NAME} SYSTEM INTERFACE "${CMAKE_SOURCE_DIR}/vendor/${ARG_INCLUDE_DIR}")
else()
target_include_directories(${NAME} SYSTEM INTERFACE "${CMAKE_SOURCE_DIR}/vendor/${NAME}/include")
endif()
endif()
endmacro()
# -----------------------------------------------------------------------
# add_vendor_subdirectory(SUBDIR)
#
# EXCLUDE_FROM_ALL means only targets actually depended on via
# target_link_libraries get built. SYSTEM marks its headers so our
# per-module warning flags (added only by add_lib_module/add_exe_module/
# etc., never globally) don't fire when *our* code includes them.
# -----------------------------------------------------------------------
macro(add_vendor_subdirectory SUBDIR)
get_property(_pmn_vendor_added GLOBAL PROPERTY PMN_VENDOR_ADDED_${SUBDIR} SET)
if(NOT _pmn_vendor_added)
set_property(GLOBAL PROPERTY PMN_VENDOR_ADDED_${SUBDIR} TRUE)
add_subdirectory(
"${CMAKE_SOURCE_DIR}/vendor/${SUBDIR}"
"${CMAKE_BINARY_DIR}/vendor/${SUBDIR}"
EXCLUDE_FROM_ALL SYSTEM
)
_exclude_from_compile_commands("${CMAKE_SOURCE_DIR}/vendor/${SUBDIR}")
endif()
endmacro()
# -----------------------------------------------------------------------
# add_dependency(NAME <FetchContent_Declare args...>)
#
# Example -- prefer an installed copy that's new enough, fetch+build from
# source otherwise:
# add_dependency(fmt
# GIT_REPOSITORY https://github.com/fmtlib/fmt.git
# GIT_TAG 12.1.0
# GIT_SHALLOW TRUE
# FIND_PACKAGE_ARGS 12 NAMES fmt
# )
# add_lib_module(mylib DEPENDS fmt::fmt)
#
# Always give FIND_PACKAGE_ARGS a minimum version (the "12" above). Without
# one, ANY installed copy beats the pinned GIT_TAG -- including a distro
# package years older than the pin -- so a "pinned" dependency isn't. A
# dependency's own CMake options (fmt's FMT_MODULE, say) are set with
# set(<OPTION> <value> CACHE ...) BEFORE this call. source/Core/CMakeLists.txt
# is the real, commented instance of both.
#
# FetchContent_MakeAvailable() is documented idempotent per name, so
# calling this more than once for the same NAME (from multiple modules)
# is safe.
# -----------------------------------------------------------------------
macro(add_dependency NAME)
include(FetchContent)
FetchContent_Declare(${NAME} SYSTEM ${ARGN})
FetchContent_MakeAvailable(${NAME})
string(TOLOWER "${NAME}" _pmn_lc_name)
if(DEFINED ${_pmn_lc_name}_SOURCE_DIR)
_exclude_from_compile_commands("${${_pmn_lc_name}_SOURCE_DIR}")
endif()
endmacro()