为什么80%的码农都做不了架构师？>>> 
环境
编译器：arm-linux-gnueabihf-gcc4.8.2（linaro即Cohda系统所用的编译器）
系统：Ubuntu14.04
QT源码：qt-everywhere-opensource-src-5.3.2（或qt-everywhere-opensource-src-4.8.2）
编译
添加arm-linux-gnueabihf-gcc4.8.2
vim /etc/profile
在profile最后一行加上gcc目录（以下为本人目录）
export PATH=$PATH:/opt/gcc-linaro-arm-linux-gnueabihf/gcc-linaro-arm-linux-gnueabihf-4.8.2/bin
保存退出，并执行这个命令加载新的环境变量
source /etc/profile
注意：这个命令有可能只在当前的终端加载新的环境变量，如果新开一个终端窗口又要用新的环境变量可以再执行一次这个名或者重启电脑
在终端输入arm-linux-gnueabihf-在按两下Tab键，正常就会有以下提示
qt@qt-virtual-machine:~$ arm-linux-gnueabihf-
arm-linux-gnueabihf-addr2line arm-linux-gnueabihf-gprof
arm-linux-gnueabihf-ar arm-linux-gnueabihf-ld
arm-linux-gnueabihf-as arm-linux-gnueabihf-ld.bfd
arm-linux-gnueabihf-c++ arm-linux-gnueabihf-ldd
arm-linux-gnueabihf-c++filt arm-linux-gnueabihf-ld.gold
arm-linux-gnueabihf-cpp arm-linux-gnueabihf-nm
arm-linux-gnueabihf-elfedit arm-linux-gnueabihf-objcopy
arm-linux-gnueabihf-g++ arm-linux-gnueabihf-objdump
arm-linux-gnueabihf-gcc arm-linux-gnueabihf-pkg-config
arm-linux-gnueabihf-gcc-4.8.2 arm-linux-gnueabihf-pkg-config-real
arm-linux-gnueabihf-gcc-ar arm-linux-gnueabihf-ranlib
arm-linux-gnueabihf-gcc-nm arm-linux-gnueabihf-readelf
arm-linux-gnueabihf-gcc-ranlib arm-linux-gnueabihf-size
arm-linux-gnueabihf-gcov arm-linux-gnueabihf-strings
arm-linux-gnueabihf-gdb arm-linux-gnueabihf-strip
arm-linux-gnueabihf-gfortran
修改qt配置
修改qtbase/mkspecs/linux-arm-gnueabi-g++/qmake.conf（qt-everywhere-opensource-src-4.8.2下mkspecs直接在根目录下），如下
#
# qmake configuration for building with arm-linux-gnueabi-g++
#
MAKEFILE_GENERATOR = UNIX
CONFIG += incremental
QMAKE_INCREMENTAL_STYLE = sublib
#新增变量
QT_QPA_DEFAULT_PLATFORM = linuxfb
QMAKE_CFLAGS_RELEASE += -O2 -march=armv7-a
QMAKE_CXXFLAGS_RELEASE += -O2 -march=armv7-a
include(../common/linux.conf)
include(../common/gcc-base-unix.conf)
include(../common/g++-unix.conf)
#修改后的变量，更具实际情况修改
# modifications to g++.conf
QMAKE_CC = arm-linux-gnueabihf-gcc-4.8.2
QMAKE_CXX = arm-linux-gnueabihf-g++
QMAKE_LINK = arm-linux-gnueabihf-g++
QMAKE_LINK_SHLIB = arm-linux-gnueabihf-g++
# modifications to linux.conf
QMAKE_AR = arm-linux-gnueabihf-ar cqs
QMAKE_OBJCOPY = arm-linux-gnueabihf-objcopy
QMAKE_NM = arm-linux-gnueabihf-nm -P
QMAKE_STRIP = arm-linux-gnueabihf-strip
load(qt_config)
设置config
在Qt源码根目录新建一个autoconfig.sh文件，并将以下内容复制进去
#!/bin/sh
./configure \
-prefix /opt/qt-everywhere-arm-linux/qt-everywhere-arm-linux-5.3.2 \
-confirm-license \
-opensource \
-release \
-make libs \
-xplatform linux-arm-gnueabi-g++ \
-optimized-qmake \
-pch \
-qt-sql-sqlite \
-qt-libjpeg \
-qt-libpng \
-qt-zlib \
-no-opengl \
-no-sse2 \
-no-openssl \
-no-nis \
-no-cups \
-no-glib \
-no-dbus \
-no-xcb \
-no-qpa-platform-guard \
-no-xcursor -no-xfixes -no-xrandr -no-xrender \
-no-separate-debug-info \
-make examples -nomake tools -nomake tests -no-iconv \
-qreal float \
-v
exit
-prefix qt的安装目录（make install的安装目录）
-opensource 开源声明
-confirm-license 接受上面的开源声明，如果没有这项，每次执行是都需要手动确认
-xplatform 编译平台选择，参数填qmake.conf所在的文件夹名称
-qreal float 指定qreal类型，默认是double，（只有在Arm平台上，qreal是float，其他情况下qreal是double）
-v 输出详细信息
更多的参数可以通过以下命令查看
./configure -help
也可将帮助文档保存到文件
./configure -help > help.txt
另附上qt-everywhere-opensource-src-4.8.2的autoconfig.sh的内容
#!/bin/bash
./configure \
-prefix /opt/qt-everywhere-arm-linux/qt-everywhere-arm-linux-4.8.2 \
-opensource \
-confirm-license \
-release -shared \
-embedded arm \
-xplatform linux-arm-gnueabi-g++ \
-depths 16,18,24 \
-fast \
-optimized-qmake \
-pch \
-qt-sql-sqlite \
-qt-libjpeg \
-qt-zlib \
-qt-libpng \
-qt-freetype \
-little-endian -host-little-endian \
-no-qt3support \
-no-libtiff -no-libmng \
-no-opengl \
-no-mmx -no-sse -no-sse2 \
-no-3dnow \
-no-openssl \
-no-webkit \
-no-qvfb \
-no-phonon \
-no-nis \
-no-opengl \
-no-cups \
-no-glib \
-no-xcursor -no-xfixes -no-xrandr -no-xrender \
-no-separate-debug-info \
-nomake examples -nomake tools -nomake docs \
-lrt
exit
生成Makefile
完成第三步后，实行下面的命令生成Makefile文件
sh autoconfig.sh
如果执行成功就会输出如下信息并且生成Makefile
Creating qmake...
make: Nothing to be done for `first'.
Running configuration tests...
Warning: Disabling pkg-config since PKG_CONFIG_LIBDIR is not set.
Warning: Disabling pkg-config since PKG_CONFIG_SYSROOT_DIR is not set.
Configure summary
Building on: linux-g++ (x86_64, CPU features: mmx sse sse2)
Building for: linux-arm-gnueabi-g++ (arm, CPU features:)
Platform notes:
- Also available for Linux: linux-kcc linux-icc linux-cxx
Build options:
Configuration .......... accessibility audio-backend c++11 clock-gettime clock-monotonic compile_examples concurrent cross_compile evdev eventfd freetype full-config getaddrinfo getifaddrs inotify ipv6ifname large-config largefile linuxfb medium-config minimal-config mremap no-harfbuzz no-pkg-config pcre png posix_fallocate precompile_header qpa qpa reduce_exports release rpath shared small-config zlib
Build parts ............ libs examples
Mode ................... release
Using C++11 ............ yes
Using PCH .............. yes
Target compiler supports:
iWMMXt/Neon .......... no/auto
Qt modules and options:
Qt D-Bus ............... no
Qt Concurrent .......... yes
Qt GUI ................. yes
Qt Widgets ............. yes
Large File ............. yes
QML debugging .......... yes
Use system proxies ..... no
Support enabled for:
Accessibility .......... yes
ALSA ................... no
CUPS ................... no
Evdev .................. yes
FontConfig ............. no
FreeType ............... yes (bundled copy)
Glib ................... no
GTK theme .............. no
HarfBuzz ............... no
Iconv .................. no
ICU .................... no
Image formats:
GIF .................. yes (plugin, using bundled copy)
JPEG ................. yes (plugin, using bundled copy)
PNG .................. yes (in QtGui, using bundled copy)
journald ............... no
mtdev .................. no
Networking:
getaddrinfo .......... yes
getifaddrs ........... yes
IPv6 ifname .......... yes
OpenSSL .............. no
NIS .................... no
OpenGL / OpenVG:
EGL .................. no
OpenGL ............... no
OpenVG ............... no
PCRE ................... yes (bundled copy)
pkg-config ............. no
PulseAudio ............. no
QPA backends:
DirectFB ............. no
EGLFS ................ no
KMS .................. no
LinuxFB .............. yes
XCB .................. no
Session management ..... yes
SQL drivers:
DB2 .................. no
InterBase ............ no
MySQL ................ no
OCI .................. no
ODBC ................. no
PostgreSQL ........... no
SQLite 2 ............. no
SQLite ............... qt-qt
TDS .................. no
udev ................... no
xkbcommon .............. no
zlib ................... yes (bundled copy)
Qt is now configured for building. Just run 'make'.
Once everything is built, you must run 'make install'.
Qt will be installed into /opt/qt-everywhere-arm-linux/qt-everywhere-arm-linux-5.3.2
Prior to reconfiguration, make sure you remove any leftovers from
the previous build.
编译
make
或者多线程编译，8为线程数
make -j8
安装
sudo make install
配置qt环境
在/etc/profile文件最后添加/opt/qt-everywhere-arm-linux/qt-everywhere-arm-linux-5.3.2/bin，最后别忘了
source /etc/profile
命令行编译及运行应用
进入应用跟目录，假如目录名是mainwindow
qmake -project #生成.pro文件，这里生成mainwindow.pro
qmake mainwindow.pro #生成Makefile
make #编译，生成mainwindow可执行文件
./mainwindow #运行程序
问题集锦
说明：问题1-4都是在编译qt-everywhere-opensource-src-4.8.2源码时遇到的
找不到libstdc++.so.6库
arm-linux-gnueabihf-g++: error while loading shared libraries: libstdc++.so.6: cannot open shared object file: No such file or directory
解决方法
$sudo apt-get install libstdc++6
$sudo apt-get install lib32stdc++6
ubuntu更新源地址找不到
解决方法
打开设置->软件&更新->download from->其它（选择一个国内的源地址）
未定义clock_gettime
.obj/release-shared-emb-arm/qtconcurrentiteratekernel.o: In function `getticks()':
qtconcurrentiteratekernel.cpp:(.text+0x1a): undefined reference to `clock_gettime'
解决方法
修改：vim src/corelib/Makefile 加上-lrt
LIBS = $(SUBLIBS) -L/opt/qt-everywhere-opensource-src-4.8.4/lib -lpthread -lm -ldl -lrt
未定义'dlerror@GLIBC_2.4'
编译QT报的错
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlerror@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlclose@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlopen@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlsym@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `clock_gettime@GLIBC_2.4'
编译应用报的错
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlerror@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlclose@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlopen@GLIBC_2.4'
/home/qt/yxmsw2007/qt-everywhere-opensource-src-4.8.2/lib/libQtCore.so: undefined reference to `dlsym@GLIBC_2.4'
collect2: error: ld returned 1 exit status
make: *** [applicationicon] Error 1
解决方法
编译的时候报了一次，执行了make confclean后再次make就正常 编译完成后，在编译应用时又报了这个错，于是修改了应用的Makefile中的LFLAGS和LIBS的引用路径
网上修改建议
qtlib = /opt/qt-4.8.5-arm/lib/
#/home/DTV1000/install/lib
LFLAGS = -Wl,-O1 -Wl,-rpath,$(qtlib)
LIBS = $(SUBLIBS) -L$(qtlib) -lQtGui -L$(qtlib) -lts -lQtNetwork -lQtCore -lm -lrt -ldl -lpthread
实际修改
qtlib = /opt/qt-everywhere-arm-linux-4.8.2/lib/
LFLAGS = -Wl,-rpath-link,$(qtlib) -Wl,-O1 -Wl,-rpath,$(qtlib)
LIBS = $(SUBLIBS) -L$(qtlib) -lQtGui -L$(qtlib) -lQtNetwork -lQtCore -lm -lrt -ldl -lpthread