Building the LLVM C/C++ Front-End

- -

This section describes how to acquire and build llvm-gcc 4.0 and 4.2, which are -based on the GCC 4.0.1/4.2.1 front-ends respectively. Both front-ends support C, -C++, Objective-C and Objective-C++. The 4.2 front-end also supports Ada and -Fortran to some extent. Note that the instructions for building these front-ends -are completely different (and much easier!) than those for building llvm-gcc3 in -the past.

- -

Retrieve the appropriate llvm-gcc4.x-y.z.source.tar.gz archive from the - llvm web site.
- -
It is also possible to download the sources of the llvm-gcc front end - from a read-only mirror using subversion. To check out the 4.0 code - for first time use:
- -
-
```
-svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.0/trunk dst-directory
-
```
-
- -
To check out the 4.2 code use:
- -
-
```
-svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk dst-directory
-
```
-
- -
After that, the code can be be updated in the destination directory - using:
- -
-
```
svn update
```
-
- -
The mirror is brought up to date every evening.
Follow the directions in the top-level README.LLVM file for - up-to-date instructions on how to build llvm-gcc. See below for building - with support for Ada or Fortran. -

- -

-

Building with support for Ada amounts to following the directions in the -top-level README.LLVM file, adding ",ada" to EXTRALANGS, for example: -EXTRALANGS=,ada

- -

There are some complications however:

- -

The only platform for which the Ada front-end is known to build is - 32 bit intel x86 running linux. It is unlikely to build for other - systems without some work.
The build requires having a compiler that supports Ada, C and C++. - The Ada front-end is written in Ada so an Ada compiler is needed to - build it. The LLVM parts of llvm-gcc are written in C++ so a C++ - compiler is needed to build them. The rest of gcc is written in C. - Some linux distributions provide a version of gcc that supports all - three languages (the Ada part often comes as an add-on package to - the rest of gcc). Otherwise it is possible to combine two versions - of gcc, one that supports Ada and C (such as - GNAT GPL Edition) and another - which supports C++, see below.

- -

Supposing appropriate compilers are available, llvm-gcc with Ada support can - be built using the following recipe:

- -

Download the LLVM source - and unpack it:

- -

-

wget http://llvm.org/releases/2.2/llvm-2.2.tar.gz
-tar xzf llvm-2.2.tar.gz
-mv llvm-2.2 llvm

-

- -

or check out the - latest version from subversion:

- -

-

svn co http://llvm.org/svn/llvm-project/llvm/trunk llvm

-

Download the - llvm-gcc-4.2 source - and unpack it:

- -

-

wget http://llvm.org/releases/2.2/llvm-gcc4.2-2.2.source.tar.gz
-tar xzf llvm-gcc4.2-2.2.source.tar.gz
-mv llvm-gcc4.2-2.2.source llvm-gcc-4.2

-

- -

or check out the - latest version from subversion:

- -

-

svn co http://llvm.org/svn/llvm-project/llvm-gcc-4.2/trunk llvm-gcc-4.2

-

Make a build directory llvm-objects for llvm and make it the - current directory:
- -
-
```
mkdir llvm-objects
-cd llvm-objects
```
-
-
Configure LLVM (here it is configured to install into /usr/local):
- -
-
```
../llvm/configure --prefix=/usr/local
```
-
- -
If you have a multi-compiler setup and the C++ compiler is not the - default, then you can configure like this:
- -
-
```
CXX=PATH_TO_C++_COMPILER ../llvm/configure --prefix=/usr/local
```
-
-
Build LLVM:
- -
-
```
make
```
-
-
Install LLVM (optional):
- -
-
```
make install
```
-
-
Make a build directory llvm-gcc-4.2-objects for llvm-gcc and make it the - current directory:
- -
-
```
-cd ..
-mkdir llvm-gcc-4.2-objects
-cd llvm-gcc-4.2-objects
```
-
-

Configure llvm-gcc (here it is configured to install into /usr/local). - Additional languages can be appended to the --enable-languages switch, - for example --enable-languages=ada,c,c++.

- -

-

../llvm-gcc-4.2/configure --prefix=/usr/local --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib

-

- -

If you have a multi-compiler setup, then you can configure like this:

-

- -

-export CC=PATH_TO_C_AND_ADA_COMPILER
-export CXX=PATH_TO_C++_COMPILER
-../llvm-gcc-4.2/configure --prefix=/usr/local --enable-languages=ada,c --enable-checking --enable-llvm=$PWD/../llvm-objects --disable-shared --disable-bootstrap --disable-multilib

-

Build and install the compiler:
- -
-
```
make
-make install
```
-
-

- -

-

-To build with support for Fortran, follow the directions in the top-level -README.LLVM file, adding ",fortran" to EXTRALANGS, for example:

- -

-

-EXTRALANGS=,fortran
-

-

- -

-

-The LLVM GCC frontend is licensed to you under the GNU General Public License -and the GNU Lesser General Public License. Please see the files COPYING and -COPYING.LIB for more details. -

- -

-More information is available in the FAQ. -

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