This document provides instructions to upgrade GCC to version 4.9.0 and install Qt 5.4.1 on CentOS 6.5. It describes downloading and compiling GCC from source, setting it as the default compiler, and copying libraries. It also covers downloading and running the Qt 5.4.1 installer, adding Qt commands to the PATH, and copying pkg-config files. The goal is to support C++11 and have a newer compiler and Qt version on the older CentOS 6.5 operating system.

1. P.1
Upgrade GCC & Install Qt 5.4
On CentOS 6.5
William.L
wiliwe@gmail.com
2015-05-14

2. P.2
Index
Install/Upgrad GCC Supporting C++11 or above Standard ............................................................................ 3
Install Qt 5 ............................................................................................................................................................. 7

3. P.3
Install/Upgrad GCC Supporting C++11 or above
Standard
For some librariese that need GCC C++ compiler supporting C++11 or above standard mandatorily, so it would
fail to build on CentOS 6.5 whose GCC’s version is v4.4.7, it is too old.
From GCC v4.7, GCC supports C++11 standard; from GCC v4.9, GCC supports C++14 standard.
Here using GCC v4.9.0 as an example for upgrading GCC on CentOS 6.5.
To retrieve a copy of GCC source archive, please refer to the GNU GCC download site:
* ftp://ftp.gnu.org/gnu/gcc/
* http://ftp.gnu.org/gnu/gcc/
* https://ftp.gnu.org/gnu/gcc/
1) Dowload GCC v4.9.0 source archive.
# curl -O http://ftp.gnu.org/gnu/gcc/gcc-4.9.0/gcc-4.9.0.tar.gz
or
# wget http://ftp.gnu.org/gnu/gcc/gcc-4.9.0/gcc-4.9.0.tar.gz
2) Unpack gcc-4.9.0.tar.gz, it will generate a folder name “gcc-4.9.0”:
# tar zxf gcc-4.9.0.tar.gz
3) Install development tools (if you do not install it ever).
# yum groupinstall "Development tools"

4. P.4
4) Download and extract pre-requisites
These prerequisites are required to build the final gcc compiler.
# cd gcc-4.9.0
# ./contrib/download_prerequisites

5. P.5
Note:
* It must locate in this level of directory because the pre-requisite packages must be put in this level!
* If you do not install required libraries for building GCC, it will show below error messages.
5) Configure and install GCC
# cd ..
# mkdir build_gcc_4.9.0
# cd build_gcc_4.9.0
# ../gcc-4.9.0/configure --prefix=/opt/gcc-4.9.0/ --enable-checking=release --enable-languages=c,c++ --disable-multilib
# make -j4 (4 means 4 CPU cores, this will change on different CPU platform)
# make -k check
# make install
Note
On 64-bit (x86_64) platform, when confguring GCC, use the option
"--enable-multilib --with-multilib-list=m32,m64" to let compiler could build out a 32-bit software, while
the option "--disable-multilib" means no 32-bit support, e.g. it could only built out 64-bit software.
6) Using alternatives(or ”update-alternatives“ which is a symbolic link to “alternatives”) tool to set currently
used GCC compiler. The version of GCC used in CentOS 6.5 is v4.4.7.
# mv /usr/bin/gcc /usr/bin/gcc_4.4.7
# update-alternatives --install /usr/bin/gcc gcc /opt/gcc-4.9.0/bin/x86_64-unknown-linux-gnu-gcc-4.9.0 40
# mv /usr/bin/g++ /usr/bin/g++_4.4.7
# update-alternatives --install /usr/bin/g++ g++ /opt/gcc-4.9.0/bin/g++ 40
# mv /usr/bin/c++ /usr/bin/c++_4.4.7
# update-alternatives --install /usr/bin/c++ c++ /opt/gcc-4.9.0/bin/c++ 40
To verify current version of GCC compiler.
# gcc --version

6. P.6
# g++ --version
# c++ --version
7) Copy new GCC libraries to system library folder
[for 32-bit]
# mv /usr/lib/libstdc++.so.6 /usr/lib/libstdc++.so.6.backup
# cp -P /opt/gcc-4.9.0/lib/libstdc++.so.6 /usr/lib/
# cp /opt/gcc-4.9.0/lib/libstdc++.so.6.0.20 /usr/lib/
[for 64-bit]
# mv /usr/lib64/libstdc++.so.6 /usr/lib64/libstdc++.so.6.backup
# cp -P /opt/gcc-4.9.0/lib64/libstdc++.so.6 /usr/lib64/
# cp /opt/gcc-4.9.0/lib64/libstdc++.so.6.0.20 /usr/lib64/
To verify current version of all system libraries
# ldconfig -v
If you want to update the “man” document for the new GCC, it could copy folders and files under
/opt/gcc-4.9.0/share to /usr/lib/share or /usr/lib64/share.

7. P.7
Install Qt 5
Here using Qt v5.4.1 for example.
1) Install Development Tools (if you do not install it ever)
# su
$ yum groupinstall "Development Tools"

8. P.8
2) Download qt -opensource-linux-x64-5.4.1.run or latest version
* http://download.qt.io/archive/qt/
* http://download.qt.io/archive/qt/5.4/5.4.1/
* http://download.qt.io/archive/qt/5.4/5.4.1/qt-opensource-linux-x64-5.4.1.run.mirrorlist
3) Change the mode of to executable
# chmod 755 ./qt-opensource-linux-x64-5.4.1.run
4) Run qt-opensource-linux-x64-5.4.1.run to start installation process
# ./qt-opensource-linux-x64-5.4.1.run

9. P.9

10. P.10

11. P.11

12. P.12
Note
If the GCC(g++ / c++ compiler) version does not support C++10 (or above) standard, it will show below error
messages.

13. P.13
It could use commands to check if there have needed C++ libraries in the system.
# strings /usr/lib64/libstdc++.so.6 | grep GLIBC
Below shows CentOS 6.5 original C++ libraries.
If you ever upgrade GCC to a newer version, it would show more libraries (here is the case that it had
upgrade GCC to v4.9.0).

14. P.14
5) Add Qt commands to PATH (e.g. qmake).
Ex:
export PATH=$PATH :/home/william/Qt5.4.1/5.4/gcc_64/bin
6) Run qmake -version to verify the version.
7) Copy built Qt 5.4.1 library’s pkg-config(package configuration) file (.pc) to system library folder for 64-bit,
/usr/lib64/pkgconfig.
su
cd /usr/lib64/
cp -r ./pkgconfig ./ pkgconfig_org
cd ./pkgconfig
cp /home/william/Qt5.4.1/5.4/gcc_64/lib/pkgconfig/* ./

15. P.15
Note
/home/william/Qt5.4.1 is Qt 5.4.1 installation path.
About pkg-config, please see its official site:
http://www.freedesktop.org/wiki/Software/pkg-config/
Reference
* https://wiki.qt.io/How-to-Install-Qt-5-and-Qwt-on-CentOS-6
* https://rajivpandit.wordpress.com/2013/11/15/install-qt5-on-centos-6-4-and-fix-glibcxx_3-4-15-not-found-error-in-qt5-install/