Java 2 Ada

GCC 6.1 Ada Compiler From Scratch

By stephane.carrez

GCC 6.1 release has been announced recently by Jakub Jelinek and it is now time to build a new Ada compiler with it. The process to do that is not complex but contains a few pitfalls. We will do the following tasks:

  1. The binutils build and installation,
  2. The gcc build and installation,
  3. Setting up a default configuration for gprbuild,
  4. The XML/Ada build and installation,
  5. The gprbuild build and installation.

Pre-requisites

First, prepare three distinct directories for the sources, the build materials and the installation. Make sure you have more than 1.5G for the source directory, reserve 7.0G for the build directory and arround 1.5G for the installation directory.

To simplify the commands, define the following shell variables:

BUILD_DIR=<Path of build directory>
INSTALL_DIR=<Path of installation directory>
SRC_DIR=<Path of directory containing the extracted sources>

Also, check that:

  • You have a GNAT Ada compiler installed (at least a 4.9 I guess).
  • You have the gprbuild tool installed and configured for the Ada compiler.
  • You have libmpfr-dev, libgmp3-dev and libgmp-dev installed (otherwise this is far more complex).
  • You have some time and can wait for gcc's compilation (it took more than 2h for me).

Create the directories:

mkdir -p $BUILD_DIR
mkdir -p $INSTALL_DIR/bin
mkdir -p $SRC_DIR

And setup your PATH so that you will use the new binutils and gcc commands while building everything:

export PATH=$INSTALL_DIR/bin:/usr/bin:/bin

Binutils

Download binutils 2.26 and extract the tar.bz2 in the source directory $SRC_DIR.

cd $SRC_DIR
tar xf binutils-2.26.tar.bz2

Never build the binutils within their sources, you must use the $BUILD_DIR for that. Define the installation prefix and configure the binutils as this:

mkdir $BUILD_DIR/binutils
cd $BUILD_DIR/binutils
$SRC_DIR/binutils-2.26/configure --prefix=$INSTALL_DIR

And proceed with the build in the same directory:

make

Compilation is now complete you can install the package:

make install

Gcc

Download gcc 6.1.0 and extract the tar.bz2 in the source directory $SRC_DIR.

cd $SRC_DIR
tar xf gcc-6.1.0.tar.bz2

Again, don't build gcc within its sources and use the $BUILD_DIR directory. At this stage, it is important that your PATH environment variable uses the $INSTALL_DIR/bin first to make sure you will use the new installed binutils tools. You may add the --disable-bootstrap to speed up the build process.

mkdir $BUILD_DIR/gcc
cd $BUILD_DIR/gcc
$SRC_DIR/gcc-6.1.0/configure --prefix=$INSTALL_DIR --enable-languages=c,c++,ada

And proceed with the build in the same directory (go to the restaurant or drink a couple of beers while it builds):

make

Compilation is now complete you can install the package:

make install

The Ada compiler installation does not install two symbolic links which are required during the link phase of Ada libraries and programs. You must create them manually after the install step:

ln -s libgnarl-6.so $INSTALL_DIR/lib/gcc/x86_64-pc-linux-gnu/6.1.0/adalib/libgnarl-6.1.so
ln -s libgnat-6.so $INSTALL_DIR/lib/gcc/x86_64-pc-linux-gnu/6.1.0/adalib/libgnat-6.1.so

Setup the default.cgpr file

The gnatmake command has been deprecated and it is now using gprbuild internally. This means we need a version of gprbuild that uses the new compiler. One way to achieve that is by setting up a gprbuild configuration file:

cd $BUILD_DIR
gprconfig

Select the Ada and C compiler and then edit the default.cgpr file that was generated to change the Toolchain_Version, Runtime_Library_Dir, Runtime_Source_Dir, Driver to indicate the new gcc 6.1 installation paths (replace <INSTALL_DIR> with your installation directory):

configuration project Default is
   ...
   for Toolchain_Version     ("Ada") use "GNAT 6.1";
   for Runtime_Library_Dir   ("Ada") use "<INSTALL_DIR>/lib/gcc/x86_64-pc-linux-gnu/6.1.0//adalib/";
   for Runtime_Source_Dir    ("Ada") use "<INSTALL_DIR>/lib/gcc/x86_64-pc-linux-gnu/6.1.0//adainclude/";
   package Compiler is
      for Driver ("C") use "<INSTALL_DIR>/bin/gcc";
      for Driver ("Ada") use "<INSTALL_DIR>/bin/gcc";
      ...
   end Compiler;
   ...
end Default;

This is the tricky part because if you missed it you may end up using the old Ada compiler. Make sure the Runtime_Library_Dir and Runtime_Source_Dir are correct otherwise you'll have problems during builds. As far as I'm concerned, the gcc target triplet was also changed from x86_64-linux-gnu to x86_64-pc-linux-gnu. Hopefully, once we have built a new gprbuild everything will be easier. The next step is to build XML/Ada which is used by gprbuild.

XML/Ada

Download and extract the XML/Ada sources. Using the git repository works pretty well:

cd $BUILD_DIR
git clone https://github.com/AdaCore/xmlada.git xmlada

This time we must build within the sources. Before running the configure script, the default.cgpr file is installed so that the new Ada compiler is used:

cp $BUILD_DIR/default.cgpr $BUILD_DIR/xmlada/
cd $BUILD_DIR/xmlada
./configure --prefix=$INSTALL_DIR

And proceed with the build in the same directory:

make static shared

Compilation is now complete you can install the package:

make install-static install-relocatable

gprbuild

Get the gprbuild sources from the git repository:

cd $BUILD_DIR
git clone https://github.com/AdaCore/gprbuild.git gprbuild

Copy the default.cgpr file to the gprbuild source tree and run the configure script:

cp $BUILD_DIR/default.cgpr $BUILD_DIR/gprbuild/
cd $BUILD_DIR/gprbuild
./configure --prefix=$INSTALL_DIR

Setup the ADA_PROJECT_PATH environment variable to use the XML/Ada library that was just compiled. If you miss this step, you'll get a file dom.ali is incorrectly formatted error during the bind process.

export ADA_PROJECT_PATH=$INSTALL_DIR/lib/gnat

And proceed with the build in the same directory:

make

Compilation is now complete you can install the package:

make install

Using the compiler

Now you can remove the build directory to make some space. You'll not need the default.cgpr file anymore nor define the ADA_PROJECT_PATH environment variable (except for other needs). To use the new Ada compiler you only need to setup your PATH:

export PATH=$INSTALL_DIR/bin:/usr/bin:/bin

You're now ready to play and use the GCC 6.1 Ada Compiler.

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