[C++][CMake] set_target_properties called with incorrect number of arguments

1 简介

这篇文章将探讨了在使用CMake构建C++项目时，调用set_target_properties函数时参数数量不正确所引发的问题。

2 错误案例

以下为可能发生错误的案例

include_directories (${CMAKE_SOURCE_DIR}/common)
find_package(Threads)

add_library (libusbmuxd SHARED libusbmuxd.c sock_stuff.c ${CMAKE_SOURCE_DIR}/common/utils.c)
find_library (PTHREAD pthread)
target_link_libraries (libusbmuxd ${CMAKE_THREAD_LIBS_INIT})

# 'lib' is a UNIXism, the proper CMake target is usbmuxd
# But we can't use that due to the conflict with the usbmuxd daemon,
# so instead change the library output base name to usbmuxd here
set_target_properties(libusbmuxd PROPERTIES OUTPUT_NAME usbmuxd)
set_target_properties(libusbmuxd PROPERTIES VERSION ${LIBUSBMUXD_VERSION})
set_target_properties(libusbmuxd PROPERTIES SOVERSION ${LIBUSBMUXD_SOVERSION})

install(TARGETS libusbmuxd
    ARCHIVE DESTINATION lib${LIB_SUFFIX}
    LIBRARY DESTINATION lib${LIB_SUFFIX}
)
install(FILES usbmuxd.h usbmuxd-proto.h DESTINATION include)
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以上文件可能报错如下：

CMake error at CMakeLists.txt:12 (set_target_properties):
    set_target_properties called with incorrect number of arguments
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3 原因分析

set_target_properties 函数的语法格式为

SET_TARGET_PROPERTIES(
    target1 target2 ... targetM
    PROPERTIES 
    prop1 val1 prop2 val2 ... propN valN
)
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变量LIBUSBMUXD_VERSION和LIBUSBMUXD_SOVERSION未定义，因此命令的语法是

SET_TARGET_PROPERTIES(target PROPERTIES name value)
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很显然，这里少了value变量

4 解决方法

要解决这个问题，请尝试引用变量;使用“$ {LIBUSBMUXD_SOVERSION}”应确保即使变量未定义，它也会采用空字符串的值，从而遵守语法。

include_directories (${CMAKE_SOURCE_DIR}/common)
find_package(Threads)

add_library (libusbmuxd SHARED libusbmuxd.c sock_stuff.c ${CMAKE_SOURCE_DIR}/common/utils.c)
find_library (PTHREAD pthread)
target_link_libraries (libusbmuxd ${CMAKE_THREAD_LIBS_INIT})

# 'lib' is a UNIXism, the proper CMake target is usbmuxd
# But we can't use that due to the conflict with the usbmuxd daemon,
# so instead change the library output base name to usbmuxd here
set_target_properties(libusbmuxd PROPERTIES OUTPUT_NAME usbmuxd)
set_target_properties(libusbmuxd PROPERTIES VERSION " ${LIBUSBMUXD_VERSION}")
set_target_properties(libusbmuxd PROPERTIES SOVERSION " ${LIBUSBMUXD_SOVERSION}")

install(TARGETS libusbmuxd
    ARCHIVE DESTINATION lib${LIB_SUFFIX}
    LIBRARY DESTINATION lib${LIB_SUFFIX}
)
install(FILES usbmuxd.h usbmuxd-proto.h DESTINATION include)
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