Cross-compiling is the process of compiling an application on one machine, producing executable code for a different machine or device. To cross-compile a Qt for Embedded Linux application, use the following approach:
注意： The cross-compiling procedure has the configuration process in common with the installation procedure; i.e., you might not necessarily have to perform all the mentioned actions depending on your current configuration.
Specify which cross-compiler to use by setting the
PATH
environment variable. For example, if the current shell is bash, ksh, zsh or sh:
export PATH=path/to/cross/compiler:$PATH
The qmake tool requires a platform and compiler specific
qmake.conf
file describing the various default values, to generate the appropriate Makefiles. The standard
Qt for Embedded Linux
distribution provides such files for several combinations of platforms and compilers. These files are located in the distribution's
mkspecs/qws
子目录。
Each platform has a default specification.
Qt for Embedded Linux
will use the default specification for the current platform unless told otherwise. To override this behavior, you can use the
configure
脚本的
-platform
option to change the specification for the host platform (where compilation will take place).
The
configure
脚本的
-xplatform
option is used to provide a specification for the target architecture (where the library will be deployed).
For example, to cross-compile an application to run on a device with an ARM architecture, using the GCC toolchain, run the configure script at the command line in the following way:
./configure -embedded arm -xplatform qws/linux-arm-g++ <other options>
If neither of the provided specifications fits your target device, you can create your own. To create a custom
qmake.conf
file, just copy and customize an already existing file. For example:
cp path/to/QtEmbedded/mkspecs/qws/linux-mips-g++/... path/to/QtEmbedded/mkspecs/qws/linux-myarchitecture-g++/...
注意： When defining a mkspec for a Linux target, the directory must be prefixed with "linux-". We recommend that you copy the entire directory.
Note also that when providing you own qmake specifcation, you must use the
configure
脚本的
-xplatform
option to make
Qt for Embedded Linux
aware of the custom
qmake.conf
文件。
Starting with Qt 4, all of Qt's implicitly shared classes can safely be copied across threads like any other value classes, i.e., they are fully reentrant. This is accomplished by implementing reference counting operations using atomic hardware instructions on all the different platforms supported by Qt.
To support a new architecture, it is important to ensure that these platform-specific atomic operations are implemented in a corresponding header file (
qatomic_ARCH.h
), and that this file is located in Qt's
src/corelib/arch
directory. For example, the Intel 80386 implementation is located in
src/corelib/arch/qatomic_i386.h
.
见 实现原子操作 文档编制了解细节。
Without the proper mouse and keyboard drivers, you will not be able to give any input to your application when it is installed on the target device. You must also ensure that the appropriate screen driver is present to make the server process able to put the application's widgets on screen.
Qt for Embedded Linux provides several ready-made mouse, keyboard and screen drivers, see the pointer handling , character input and display management 文档编制了解细节。
In addition, custom drivers can be added by deriving from the
QWSMouseHandler
,
QWSKeyboardHandler
and
QScreen
classes respectively, and by creating corresponding plugins to make use of Qt's plugin mechanism (dynamically loading the drivers into the server application at runtime). Note that the plugins must be located in a location where Qt will look for plugins, e.g., the standard
plugin
目录。
见 如何创建 Qt 插件 documentation and the 插件和描绘 范例了解细节。
Before building the executable, you must specify the target architecture as well as the target specific hardware drivers by running the
configure
script:
cd path/to/QtEmbedded ./configure -embedded <architecture> -qt-kbd-<keyboarddriver> -qt-mouse-<mousedriver> -qt-gfx-<screendriver>
It is also important to make sure that all the third party libraries that the application and the Qt libraries require, are present in the tool chain. In particular, if the zlib and jpeg libraries are not available, they must be included by running the
configure
script with the
-L
and
-I
options. For example:
cd path/to/QtEmbedded ./configure <other options> -L /path/to/libjpeg/libraries -I /path/to/libjpeg/headers
The JPEG source can be downloaded from http://www.ijg.org/ 。 Qt for Embedded Linux distribution includes a version of the zlib source that can be compiled into the Qt for Embedded Linux library. If integrators wish to use a later version of the zlib library, it can be downloaded from the http://www.gzip.org/zlib/ website.
Then build the executable:
cd path/to/myApplication qmake -project qmake make
That's all. Your target specific executable is ready for deployment.
|
另请参阅：
Qt for Embedded Linux 体系结构 and Deploying Qt for Embedded Linux Applications . |
