仅当依赖项满足时才创建 CMake 目标

Question

我有一个包含多个库和可执行文件的 CMake 项目。某些目标具有可能无法在所有平台上得到满足的依赖项。在这种情况下，我希望 CMake 能够工作并生成有意义的 Makefile（或其他构建项目）。

例如：

libFOO -> 取决于 libX11（比如）
execBAR -> 取决于 libFOO
exexQUUX -> 无部门

在安装了 libX11 的系统上，可以构建所有目标。在没有的系统上，只能构建 execQUUX。

目前我正在做这样的事情：

# work out if we can build this target
set(buildLibFOO LibX11_FOUND)

if (${buildLibFOO})
    add_library(libFOO ... )
    target_link_libraries(libFOO LibX11_LIBRARY)
endif()

set(buildExecBAR true)

# work out if we can build this target
if (NOT TARGET libFOO)
    set(buildExecBAR false)
endif()

if (${buildExecBAR})
    add_exec(execBAR ...)
    target_link_libraries(execBAR libFOO)
endif() 

# always build this one
add_exec(execQUUX ...)

然而，这感觉有点笨拙，因为我需要仔细考虑为每个目标检查什么，而不是告诉 CMake "these deps are required for these targets, if missing, omit the target"。

有没有更简单（或更正确）的方法来做到这一点？

Answer 1

these deps are required for these targets, if missing, omit the target

据我所知，CMake中没有这样的功能。

但是您可以创建函数，它仅在满足其依赖项时才添加 library/executable。像这样：

include(CMakeParseArguments)

# Similar as *add_executable*, but additionally accepts DEPENDS option.
# All arguments after this option are treated as libraries targets for link with;
# executable is created only when these targets exist.
function(add_executable_depends name)
    cmake_parse_arguments(MY_EXEC "" "" "DEPENDS" ${ARGN})
    foreach(depend ${MY_EXEC_DEPENDS})
        if(NOT TARGET ${depend})
            return()
        endif()
    endforeach()
    add_executable(${name} ${MY_EXEC_UNPARSED_ARGUMENTS})
    target_link_libraries(${name} ${MY_EXEC_DEPENDS})
endfunction()

用法示例：

# work out if we can build this target
set(buildLibFOO LibX11_FOUND)

if (${buildLibFOO})
    add_library(libFOO ... )
    target_link_libraries(libFOO LibX11_LIBRARY)
endif()

# Add executable (and link with libFOO) only when libFOO exists.
add_executable_depends(execBAR ... DEPENDS libFOO)

# always build this one(similar to add_executable)
add_executable_depends(execQUUX ...)

仅当依赖项满足时才创建 CMake 目标

Create CMake target only if dependencies satisified

cmake

build-dependencies