Solarian Programmer

My programming ramblings

Building GCC 7 on Windows Subsystem for Linux

Posted on May 4, 2017 by Sol

In this article, I will show you how to compile from sources GCC 7.1 on WSL, Windows Subsystem for Linux. The default version of GCC, at the time of this writing, is 5.4 which is pretty old. GCC 7.1 has complete support for C++11, C++14 and experimental support for the current C++17 draft.

GCC 7.1 has *C++14 support enabled by default. If you want to try the new C++17 support use the -std=c++1z flag, example:

1 g++-7.1 -std=c++1z test.cpp -o test

I assume that you have a working and updated WSL installation on your Windows 10 machine. If this is not the case, check my previous article.

First, start WSL, use the Bash on Ubuntu on Windows console or write bash in a Command Prompt window. Let’s make sure that you have an up to date system, start WSL (use the Bash on Ubuntu on Windows console or write bash in a Command Prompt window) and write:

1 sudo apt update
2 sudo apt upgrade

Now, install the default GCC toolchain with:

1 sudo apt install build-essential

Next, download the GCC 7.1 source and prerequisites from http://gcc.gnu.org/mirrors.html:

1 cd ~
2 wget http://gcc.parentingamerica.com/releases/gcc-7.1.0/gcc-7.1.0.tar.bz2
3 tar xf gcc-7.1.0.tar.bz2
4 cd gcc-7.1.0
5 contrib/download_prerequisites

At this point, we can configure the build. In order to keep the system clean, we will use /usr/local/gcc-7.1 for the installation folder and append the suffix -7.1 to the GCC compilers. You typically don’t want to mess the system’s default GCC because other packages may depend on this.

1 cd ~
2 mkdir build && cd build
3 ../gcc-7.1.0/configure -v --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --prefix=/usr/local/gcc-7.1 --enable-checking=release --enable-languages=c,c++,fortran --disable-multilib --program-suffix=-7.1

Now, we are ready to build GCC, you typically want to pass twice the number of your computer cores to the make command in order to speed up the build. I have a quad-core system, so I will use 8 parallel jobs to build GCC:

1 make -j 8

Depending on the speed of your computer the build phase could take from about 30 minutes to a few hours.

Once the above phase is finished, you can install the built GCC with:

1 sudo make install

If you want to permanently add the compilers to your system’s path, use the next commands:

1 cd ~
2 echo 'export PATH=/usr/local/gcc-7.1/bin:$PATH' >> .bashrc
3 echo 'export LD_LIBRARY_PATH=/usr/local/gcc-7.1/lib64:$LD_LIBRARY_PATH' >> .bashrc
4 source .bashrc

the above will append the path to GCC 7.1 at the end of your .bashrc file.

Time to test our shiny new compilers. Open your favorite text editor and copy the next piece of code (I assume you’ll save the file as test_lambda.cpp):

1 // C++14 generalized lambda (could use "auto" for the type of a parameter)
2 #include <iostream>
3 
4 int main() {
5     std::cout << [](auto a, auto b) { return a + b; } (5, 6) << std::endl;
6     std::cout << [](auto a, auto b) { return a + b; } (5.23, 6.45) << std::endl;
7     return 0;
8 }

The code uses a generalized lambda (we could use auto for the type of the parameters), this was introduced in the C++14 standard. We can compile and test the above program with:

1 g++-7.1 -Wall -pedantic test_lambda.cpp -o test_lambda
2 ./test_lambda
3 11
4 11.68

As mentioned at the beginning of this article, GCC 7.1 has experimental support for the last C++17 standard draft. Let’s test an example of using C++17 modification to static_assert:

 1 #include <type_traits>
 2 #include <iostream>
 3 
 4 struct A {
 5     int foo;
 6 };
 7 
 8 struct B {
 9     int foo = 0;
10 };
11 
12 template <typename T>
13 void print(const T& a){
14     static_assert(std::is_pod<T>::value);
15     std::cout << a.foo << '\n';
16 }
17 
18 int main() {
19     A x{1};
20     B y{2};
21     B z;
22 
23     print<A>(x);
24     print<B>(y);
25     print<B>(z);
26 
27     return 0;
28 }

You can compile the above code if you pass std=c++1z to the compiler and you should get a compiler error triggered by lines 14 and 20 from the above code

1 g++-7.1 -std=c++1z -Wall -pedantic test_assert.cpp -o test_assert
2 test_assert.cpp: In instantiation of ‘void print(const T&) [with T = B]’:
3 test_assert.cpp:24:15:   required from here
4 test_assert.cpp:14:5: error: static assertion failed
5     static_assert(std::is_pod<T>::value);
6     ^~~~~~~~~~~~~

If you are a Fortran programmer, you can use some of the Fortran 2008 features like do concurrent with gfortran-7.1:

 1 integer,parameter::mm=100000
 2 real::a(mm), b(mm)
 3 real::fact=0.5
 4 
 5 ! initialize the arrays
 6 ! ...
 7 
 8 do concurrent (i = 1 : mm)
 9     a(i) = a(i) + b(i)
10 enddo
11 
12 end

The above code can be compiled with (supposing you’ve named it test_concurrent_do.f90s):

1 gfortran-7.1 test_concurrent_do.f90 -o test_concurrent_do
2 ./test_concurrent_do

If you are interested to learn more about the new C++11 syntax I would recommend reading The C++ Programming Language by Bjarne Stroustrup.

or, Professional C++ by M. Gregoire, N. A. Solter, S. J. Kleper 2nd edition:

If you need to brush your Fortran knowledge a good book is Modern Fortran Explained by M. Metcalf, J. Reid and M. Cohen:

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