C++ CMAKE_CXX_标志中存在重复的编译标志

我正在尝试使用cmake链接我的项目

我需要找到一个包mypack，它会给我mypack_定义、mypack_标志、mypack_include_目录和mypack_库。这里mypack_标志包含链接mypack的相关标志。我将把mypack_标志添加到CMAKE_CXX_标志

请参阅下面的CMakeLists.txt：

cmake_minimum_required(VERSION 2.8)
project(QMCLIB C CXX)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11 -fopenmp")

find_package(mypack REQUIRED)

add_executable(QMC codeA.cpp codeB.cpp )
add_definitions(${mypack_definitions})
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${mypack_flags}")
target_link_libraries(QMC ${mypack_libraries})
target_include_directories(QMC PUBLIC ${mypack_include_dirs})

然而，取决于系统，mypack_标志可能包含或不包含-fopenmp，当它包含-fopenmp时，我的CMAKE_CXX_标志将包含两个-fopenmp。我无法删除-fopenmp in

如果我删除它，当mypack_标志不包含-fopenmp时，我将在CMAKE_CXX_标志中没有-fopenmp

有没有办法强迫cmake只使用一个fopenmp？还是可以吃两杯咖啡？谢谢你的建议

======================================================================

感谢Robert Prévost，这里有一个删除重复子字符串的通用函数：

function(removeDuplicateSubstring stringIn stringOut)
    separate_arguments(stringIn)
    list(REMOVE_DUPLICATES stringIn)
    string(REPLACE ";" " " stringIn "${stringIn}")
    set(${stringOut} "${stringIn}" PARENT_SCOPE)
endfunction()

我们可以通过以下方式调用此函数：

 removeDuplicateSubstring(${CMAKE_CXX_FLAGS} CMAKE_CXX_FLAGS)

---

有一种方法可以使CMake只包含一个fopenmp。CMAKE_CXX_FLAGS是一个可以搜索子字符串的字符串。您可以根据是否已在CMAKE_CXX_标志中找到-fopenmp，有条件地添加它。假设您小心地没有添加两次，那么您可以使用下面的检查来查看是否需要添加它

# find "-fopenmp"
string(FIND ${CMAKE_CXX_FLAGS} "-fopenmp" FLAG_INDEX)
# check if we found it
if (FLAG_INDEX GREATER 0)
   message(STATUS "WE'VE GOT AT LEAST ONE!")
else()
   message(STATUS "WE'VE GOT NONE; ADD IT!")
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fopenmp")
endif()

为了安全起见，您可以删除-fopenmp的所有实例，然后将其重新添加

# remove all occurrences of "-fopenmp"
string(REPLACE "-fopenmp" "" CMAKE_CXX_FLAGS ${CMAKE_CXX_FLAGS})

除了listREMOVE_DUPLICATES解决方案之外，我建议避免使用CMAKE_CXX_标志或add_*命令，而更喜欢使用target_*命令：

; ; . 您的cmake文件可能会变成这样：

cmake_minimum_required(VERSION 2.8)
project(QMCLIB C CXX)

function(removeDuplicateSubstring stringIn stringOut)
    separate_arguments(stringIn)
    list(REMOVE_DUPLICATES stringIn)
    string(REPLACE ";" " " stringIn "${stringIn}")
    set(${stringOut} "${stringIn}" PARENT_SCOPE)
endfunction()

find_package(mypack REQUIRED)

set(mycompile_options -fopenmp ${mypack_flags})

removeDuplicateSubstring(${mycompile_options} mycompile_options)

add_executable(QMC codeA.cpp codeB.cpp )
target_compile_definitions(QMC PUBLIC ${mypack_definitions})
target_compile_options(QMC PUBLIC ${mycompile_options})
target_compile_features(QMC PUBLIC cxx_constexpr)
target_include_directories(QMC PUBLIC ${mypack_include_dirs})
target_link_libraries(QMC ${mypack_libraries})

---

非常感谢，我写了一个函数，然后是你的想法。它删除字符串中重复的子字符串。

cmake_minimum_required(VERSION 2.8)
project(QMCLIB C CXX)

function(removeDuplicateSubstring stringIn stringOut)
    separate_arguments(stringIn)
    list(REMOVE_DUPLICATES stringIn)
    string(REPLACE ";" " " stringIn "${stringIn}")
    set(${stringOut} "${stringIn}" PARENT_SCOPE)
endfunction()

find_package(mypack REQUIRED)

set(mycompile_options -fopenmp ${mypack_flags})

removeDuplicateSubstring(${mycompile_options} mycompile_options)

add_executable(QMC codeA.cpp codeB.cpp )
target_compile_definitions(QMC PUBLIC ${mypack_definitions})
target_compile_options(QMC PUBLIC ${mycompile_options})
target_compile_features(QMC PUBLIC cxx_constexpr)
target_include_directories(QMC PUBLIC ${mypack_include_dirs})
target_link_libraries(QMC ${mypack_libraries})