c++ - 如何使用 -reduce-relocations 构建 QT

Question

我正在使用 Ubuntu 16.04、cmake 3.10.1、QT 5.6.2。
以前都是在windows上开发应用，不知道在linux平台上怎么排错。

编译代码时出现错误

In file included from /usr/local/Qt/5.6.2/5.6/gcc_64/include/QtCore/qcoreapplication.h:37:0,
                 from /usr/local/Qt/5.6.2/5.6/gcc_64/include/QtWidgets/qapplication.h:37,
                 from /usr/local/Qt/5.6.2/5.6/gcc_64/include/QtWidgets/QApplication:1,
                 from /home/sulfred/Documents/SoftwareDev/github/SulfredLee/PcapReplayer/BackEnd/main.cpp:3:
/usr/local/Qt/5.6.2/5.6/gcc_64/include/QtCore/qglobal.h:1087:4: error: #error "You must build your code with position independent code if Qt was built with -reduce-relocations. " "Compile your code with -fPIC (-fPIE is not enough)."
 #  error "You must build your code with position independent code if Qt was built with -reduce-relocations. "\
    ^

Q1.
如何验证我的 Qt 是使用 -reduce-relocations 构建的。

Answer 1

在现代 CMake 中，使用 target_compile_options() 添加 -fPIC 编译标志:

add_executable(MyExecutable ...)
target_compile_options(MyExecutable PRIVATE -fPIC)

另外，Qt常常不满足于fPIE，而是需要-fPIC。使用 CMake 变量 CMAKE_POSITION_INDEPENDENT_CODE设置 fPIC 仅适用于 library 目标。此变量会将 fPIE 添加到 executable 目标，这对于 Qt 来说是不够的。因此，请使用 target_compile_options() 显式设置 fPIC。