我有一个包含第三方库依赖项的CMake项目。第三方库的标题会生成我关心源代码的警告。
CMake生成的Ninja项目（使用clang）不会为第三方库标题生成警告。
CMake生成的Xcode项目会为第三方库标题生成警告。我尝试使用CMake命令包含第三方库路径
include_directories(SYSTEM dirname1 dirname2)
但Xcode似乎没有对此信息做任何事情。
如何从CMake生成不会产生系统标头警告的Xcode项目？
Xcode命令行只是将-I附加到标头包含路径上，无论我是否将SYSTEM添加到CMake。
Darwin.cmake的以下部分不太令人鼓舞：
# Xcode does not support -isystem yet.
if(XCODE)
set(CMAKE_INCLUDE_SYSTEM_FLAG_C)
set(CMAKE_INCLUDE_SYSTEM_FLAG_CXX)
endif()
我已经对这个问题进行了小规模的再现：
== CMakeLists.txt ==
include_directories(local_headers)
include_directories(SYSTEM system_headers)
set(CMAKE_CXX_FLAGS "-Werror=unused-variable")
add_executable(main main.cpp)
== main.cpp ==
#include <system_header.h>
#include "local_header.h"
int main(int, const char**)
{
}
== system_headers/system_header.h ==
int f()
{
int x;
return 5;
}
== local_headers/local_header.h ==
int g()
{
int x = 5;
return x;
}
运行cmake -GNinja && cmake --build .版本没有错误。
运行cmake -GXcode && cmake --build .会出现以下错误：
system_headers/system_header.h:3:7: error: unused variable 'x' [-Werror,-Wunused-variable]
int x;
完整的Xcode编译路径是：
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang -x c++ -arch x86_64 -fmessage-length=0 -fdiagnostics-show-note-include-stack -fmacro-backtrace-limit=0 -Wno-trigraphs -fpascal-strings -O0 -Wno-missing-field-initializers -Wno-missing-prototypes -Wno-return-type -Wno-non-virtual-dtor -Wno-overloaded-virtual -Wno-exit-time-destructors -Wno-missing-braces -Wparentheses -Wswitch -Wno-unused-function -Wno-unused-label -Wno-unused-parameter -Wno-unused-variable -Wunused-value -Wno-empty-body -Wno-uninitialized -Wno-unknown-pragmas -Wno-shadow -Wno-four-char-constants -Wno-conversion -Wno-constant-conversion -Wno-int-conversion -Wno-bool-conversion -Wno-enum-conversion -Wno-shorten-64-to-32 -Wno-newline-eof -Wno-c++11-extensions -DCMAKE_INTDIR=\"Debug\" -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk -fasm-blocks -fstrict-aliasing -Wdeprecated-declarations -Winvalid-offsetof -mmacosx-version-min=10.11 -g -Wno-sign-conversion -I/Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Debug/include -I/Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/local_headers -I/Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/system_headers -I/Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Project.build/Debug/main.build/DerivedSources/x86_64 -I/Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Project.build/Debug/main.build/DerivedSources -Wmost -Wno-four-char-constants -Wno-unknown-pragmas -F/Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Debug -Werror=unused-variable -MMD -MT dependencies -MF /Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Project.build/Debug/main.build/Objects-normal/x86_64/main.d --serialize-diagnostics /Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Project.build/Debug/main.build/Objects-normal/x86_64/main.dia -c /Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/main.cpp -o /Users/jon/DEV/CMakeSandbox/XcodeSystemIncludes/xcode_build/Project.build/Debug/main.build/Objects-normal/x86_64/main.o
直接在命令行上运行Xcode编译命令会产生相同的错误。
答案 0 :(得分：4)
您可以通过
明确设置-isystem标志
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -isystem /path/to/system/header")
您可以通过添加编译指示
来忽略系统标头中的警告#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wunused-parameter"
#include <some/system/header.hpp> // warning ignored here
#pragma clang diagnostic pop
#include <myproject/header.hpp> // warning reported here
有关详细信息，请参阅此答案：
注意：对于这两种情况，您必须检查是否正在使用适当的编译器。例如。 -isystem在MSVC中没有意义。
答案 1 :(得分：0)
看起来答案是，“你不能”通过在CMake中使用SYSTEM来做到这一点。上面解释的解决方法可以解决这个问题。
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