将FetchContent_Declare与CMAKE_ARGS一起使用

Using FetchContent_Declare together with CMAKE_ARGS

本文关键字：一起 ARGS FetchContent Declare CMAKE      更新时间：2023-10-16

我正在使用cmakev3.13，我想将SEAL库的ExternalProject_Add()更改为：

include(FetchContent)
# Get the seal library
set(SEAL "seal")
FetchContent_Declare(
${SEAL}
GIT_REPOSITORY  https://github.com/microsoft/SEAL
GIT_TAG         v3.5.2
)
FetchContent_GetProperties(${SEAL})
if(NOT ${SEAL}_POPULATED)
FetchContent_Populate(${SEAL})
add_subdirectory(${${SEAL}_SOURCE_DIR} ${${SEAL}_BINARY_DIR})
endif()

当我使用ExternalProject_Add()我使用CMAKE_ARGS -DBUILD_SHARED_LIBS=ON时，这不适用于仅下载库FetchContent_Declare()。

SEAL v3.5.2CMakeLists.txt使用它来检查是否需要构建共享库：

# Should we build also the shared library?
set(BUILD_SHARED_LIBS_STR "Build shared library")
option(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_STR} OFF)
if(MSVC AND BUILD_SHARED_LIBS)
message(WARNING "This build system only supports a static build; disabling `BUILD_SHARED_LIBS`")
set(BUILD_SHARED_LIBS OFF CACHE BOOL ${BUILD_SHARED_LIBS_STR} FORCE)
endif()
# Conditionally build the shared library
if(BUILD_SHARED_LIBS)
add_library(seal_shared SHARED $<TARGET_OBJECTS:seal_obj>)
set_target_properties(seal_shared PROPERTIES OUTPUT_NAME seal)
seal_set_version(seal_shared)
seal_set_soversion(seal_shared)
seal_set_language(seal_shared)
seal_set_include_directories(seal_shared)
seal_link_threads(seal_shared)
# Conditionally add MSGSL include directory to build interface
if(SEAL_USE_MSGSL AND NOT MSVC)
target_include_directories(seal_shared PUBLIC $<BUILD_INTERFACE:${MSGSL_INCLUDE_DIR}>)
endif()
if(SEAL_USE_ZLIB AND NOT MSVC)
# In the shared build we link zlibstatic into the shared library
target_link_libraries(seal_shared PRIVATE zlibstatic)
endif()
seal_install_target(seal_shared SEALTargets)
endif()

有没有办法使用FetchContent_Declare()下载SEAL库，然后在构建库时使用一些CMakeLists设置将CMAKE_ARGS -DBUILD_SHARED_LIBS=ON参数传递给下载的库？

在顶层构建某个项目时，您可以使用命令行选项向其传递参数

-D<VARIABLE>=<VALUE>

(ExternalProject_Add"好像"顶级构建项目，因此选项传递在技术上是相同的(。

使用add_subdirectory方法将某个项目构建为子项目时，可以使用相同的命令行选项

-D<VARIABLE>=<VALUE>

对于顶级项目，此参数也将传播到子项目。

如果不需要将参数传递给顶级项目，则可以使用 set(缓存内部(命令流模拟CMakeLists.txt内部的参数设置：

set(<PARAMETER> <VALUE> CACHE INTERNAL "<some description>")

确保在调用之前发出此行add_subdirectory()否则不会影响子项目(。

因此，在您的情况下，您可以使用以下代码：

if(NOT ${SEAL}_POPULATED)
FetchContent_Populate(${SEAL})
# Make subproject to use 'BUILD_SHARED_LIBS=ON' setting.
set(BUILD_SHARED_LIBS ON CACHE INTERNAL "Build SHARED libraries")
add_subdirectory(${${SEAL}_SOURCE_DIR} ${${SEAL}_BINARY_DIR})
endif()

当顶级项目不使用子项目的参数集时，上述所有内容都可以完美运行。

如果顶级项目和子项目都受同一参数的影响，并且您只想对子项目的参数进行硬编码，则事情会变得更加复杂。调用后需要恢复参数add_subdirectory：

if(NOT ${SEAL}_POPULATED)
FetchContent_Populate(${SEAL})
# Store the old value of the 'BUILD_SHARED_LIBS'
set(BUILD_SHARED_LIBS_OLD ${BUILD_SHARED_LIBS})
# Make subproject to use 'BUILD_SHARED_LIBS=ON' setting.
set(BUILD_SHARED_LIBS ON CACHE INTERNAL "Build SHARED libraries")
add_subdirectory(${${SEAL}_SOURCE_DIR} ${${SEAL}_BINARY_DIR})
# Restore the old value of the parameter
set(BUILD_SHARED_LIBS ${BUILD_SHARED_LIBS_OLD} CACHE BOOL "Type of libraries to build" FORCE)
endif()
# ...
# The library will be created according to "original" value for BUILD_SHARED_LIBS option.
add_library(top_lib top_lib.c)

请注意，在恢复参数的情况下，将使用set(CACHE TYPE FORCE)命令流而不是set(CACHE INTERNAL)。这不仅会恢复 CACHE 变量的值，还会恢复其类型，如 CMake GUI 所示。

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