链接器中 CXX_FLAGS 的 CMake 交叉编译问题

Question

我在 mac os x 上有以下用于 iPhone 交叉编译的工具链：

# Platform Info
SET (CMAKE_SYSTEM_VERSION 1)
SET (CMAKE_SYSTEM_PROCESSOR arm)

# SDK Info
SET (SDKVER "3.0")
SET (DEVROOT "/Developer/Platforms/iPhoneOS.platform/Developer")
SET (SDKROOT "${DEVROOT}/SDKs/iPhoneOS${SDKVER}.sdk")
SET (CMAKE_OSX_SYSROOT "${SDKROOT}")
SET (CMAKE_OSX_ARCHITECTURES "armv6")
SET_PROPERTY(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS TRUE)

# C Compiler
SET (CMAKE_C_COMPILER "${DEVROOT}/usr/bin/arm-apple-darwin9-gcc-4.2.1")
#SET (LINK_FLAGS "-arch armv6 -arch armv7")
#SET (CMAKE_C_LINK_EXECUTABLE "${DEVROOT}/usr/bin/g++-4.2")
SET (CMAKE_C_FLAGS "-x objective-c")
SET (CMAKE_C_FLAGS_DEBUG "${CMAKE_C_FLAGS} -DDEBUG=1 -ggdb")
SET (CMAKE_C_FLAGS_RELEASE "${CMAKE_C_FLAGS} -DNDEBUG=1")
SET (CMAKE_C_FLAGS_RELWITHDEBINFO "${CMAKE_C_FLAGS} -DNDEBUG=1 -ggdb")

# CXX Compiler
SET (CMAKE_CXX_COMPILER "${DEVROOT}/usr/bin/arm-apple-darwin9-g++-4.2.1")
SET (CMAKE_CXX_FLAGS "-x objective-c++")
SET (CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS} -DDEBUG=1 -ggdb")
SET (CMAKE_CXX_FLAGS_RELEASE "${CMAKE_CXX_FLAGS} -DNDEBUG=1")
SET (CMAKE_CXX_FLAGS_RELWITHDEBINFO "${CMAKE_CXX_FLAGS} -DNDEBUG=1 -ggdb")

# Definitions
#ADD_DEFINITIONS("-arch armv6")
#ADD_DEFINITIONS("-arch armv7")
ADD_DEFINITIONS("-pipe")
ADD_DEFINITIONS("-no-cpp-precomp")
ADD_DEFINITIONS("--sysroot=${SDKROOT}")
ADD_DEFINITIONS("-miphoneos-version-min=${SDKVER}")

# System Includes
INCLUDE_DIRECTORIES(SYSTEM "${SDKROOT}/usr/include")
INCLUDE_DIRECTORIES(SYSTEM "${SDKROOT}/usr/include/c++/4.2.1")
INCLUDE_DIRECTORIES(SYSTEM "${SDKROOT}/usr/include/c++/4.2.1/armv6-apple-darwin9")
INCLUDE_DIRECTORIES(SYSTEM "${SDKROOT}/opt/iphone-${SDKVER}/include")
INCLUDE_DIRECTORIES(SYSTEM "${SDKROOT}/usr/local/iphone-${SDKVER}/include")

# System Libraries
LINK_DIRECTORIES("${SDKROOT}/usr/lib")
LINK_DIRECTORIES("${SDKROOT}/usr/lib/gcc/arm-apple-darwin9/4.2.1/")
#LINK_DIRECTORIES("${SDKROOT}/opt/iphone-${SDKVER}/lib")
#LINK_DIRECTORIES("${SDKROOT}/usr/local/iphone-${SDKVER}/lib")

# Root Paths
SET (CMAKE_FIND_ROOT_PATH "${SDKROOT}" "/opt/iphone-${SDKVER}/" "/usr/local/iphone-${SDKVER}/")
SET (CMAKE_FIND_ROOT_PATH_MODE_PROGRAM BOTH)
SET (CMAKE_FIND_ROOT_PATH_MODE_LIBRARY ONLY)
SET (CMAKE_FIND_ROOT_PATH_MODE_INCLUDE ONLY)

# CMake Parameters
SET (iPhone 1)
SET (iPhoneOS 1)
SET (iPhoneOS_VERSION ${SDKVER})
SET (CMAKE_CROSSCOMPILING 1)

#SET_TARGET_PROPERTIES(p3dm PROPERTIES LINK_FLAGS "-arch armv6 -arch armv7")

# HELPERS
#---------

MACRO(ADD_FRAMEWORK appname fwname)
    find_library(FRAMEWORK_${fwname}
        NAMES ${fwname}
        PATHS ${SDKROOT}/System/Library
        PATH_SUFFIXES Frameworks
        NO_DEFAULT_PATH)
    if( ${FRAMEWORK_${fwname}} STREQUAL FRAMEWORK_${fwname}-NOTFOUND)
        MESSAGE(ERROR ": Framework ${fwname} not found")
    else()
        TARGET_LINK_LIBRARIES(${appname} ${FRAMEWORK_${fwname}})
        MESSAGE(STATUS "Framework ${fwname} found at ${FRAMEWORK_${fwname}}")
    endif()
endmacro(ADD_FRAMEWORK)

我使用以下 CMakeLists.txt：

# PROJECT PARAMETERS
#--------------------

SET(APP_NAME p3dm)
PROJECT(${APP_NAME})

# SOURCE CODE
#-------------

SET(CMAKE_CXX_FLAGS "-x objective-c++")

INCLUDE_DIRECTORIES(SYSTEM ../inc/ ../xsrc/)

FILE(GLOB headers ../src/*.h ../xsrc/*.h)
FILE(GLOB sources ../src/*.cpp ../xsrc/*.c ../xsrc/*.cpp)

#set_source_files_properties(${sources} PROPERTIES LANGUAGE C )

# EXECUTABLE
#------------

SET(MACOSX_BUNDLE_GUI_IDENTIFIER "org.reversity.${APPNAME}")
SET(APP_TYPE MACOSX_BUNDLE)

ADD_EXECUTABLE(${APP_NAME} ${APP_TYPE} ${headers} ${sources})

SET_TARGET_PROPERTIES(${APP_NAME} PROPERTIES XCODE_ATTRIBUTE_CODE_SIGN_IDENTITY "iPhone Developer: Mario Hros")

# FRAMEWORKS
#------------

ADD_FRAMEWORK(${APP_NAME} UIKit)

我使用以下编译 bash 脚本：

#!/bin/bash

unset CPATH
unset C_INCLUDE_PATH
unset CPLUS_INCLUDE_PATH
unset OBJC_INCLUDE_PATH
unset LIBS
unset DYLD_FALLBACK_LIBRARY_PATH
unset DYLD_FALLBACK_FRAMEWORK_PATH

export SDKVER="3.0"
export DEVROOT="/Developer/Platforms/iPhoneOS.platform/Developer"
export SDKROOT="$DEVROOT/SDKs/iPhoneOS$SDKVER.sdk"
export PKG_CONFIG_PATH="$SDROOT/usr/lib/pkgconfig":"/opt/iphone-$SDKVER/lib/pkgconfig":"/usr/local/iphone-$SDKVER/lib/pkgconfig"
export PKG_CONFIG_LIBDIR="$PKG_CONFIG_PATH"
export MAINFOLDER=`pwd`

cmake . \
                         -DCMAKE_TOOLCHAIN_FILE="$MAINFOLDER/cmake/iphone-$SDKVER.toolchain" \
                         -DCMAKE_INSTALL_PREFIX="/opt/iphone-$SDKVER" \
                         "$@"

问题是，它也在链接器中使用了 CMAKE_CXX_FLAGS。编译没问题。链接看起来不错，它添加了正确的 -framework 标志，但也添加了 CMAKE_CXX_FLAGS（它们是 -x objective-c++），因此它不是链接先前编译的目标文件，它的行为就像编译目标 c++（-x 目标 c++），并且不可能链接这些对象。

我收到类似的错误

ComponentManager.cpp.o:20: error: stray '\341' in program

你不知道我做错了什么吗？

Answer 1

您可以将LINKER_LANGUAGE 设置为C 以强制CMake 将CMAKE_C_FLAGS 用于链接器。 Check it out here.

Answer 2

我通过从工具链文件中删除 CMAKE_CXX_FLAGS 和 CMAKE_C_FLAGS 并将 ADD_DEFINITIONS("-x objective-c++") 添加到 CMakeLists.txt 解决了这个问题。

这样 -x Objective-c++ 标志只传递给编译器（而不是链接器）并且只传递给我的源代码（不是在构建我的目标之前发生的 cmake 测试编译）。

Answer 3

链接命令行在 Modules/CMake{C,CXX,Fortran}Information.cmake 中设置，默认使用编译器及其编译标志（请参阅source code）。这可以通过替换构建链接命令行的规则来更改，该命令行位于变量 CMAKE_CXX_LINK_EXECUTABLE （和朋友）中。该变量不会使链接器可执行；它说明了如何链接可执行文件！

一种解决方案是设置该规则的修改形式，避免使用 CXX 标志，例如

cmake -DCMAKE_CXX_LINK_EXECUTABLE="<CMAKE_CXX_COMPILER> <FLAGS> <LINK_FLAGS> <OBJECTS> -o <TARGET> <LINK_LIBRARIES>")

但是，您可以通过不首先设置 CMAKE_CXX_FLAGS 而是将 COMPILE_FLAGS 属性添加到目标来避免此问题。