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# 2. Installation

This section describes how to install the CLN package on your system.

## 2.1 Prerequisites

### 2.1.1 C++ compiler

To build CLN, you need a C++ compiler. Actually, you need GNU `g++ 2.90` or newer, the EGCS compilers will do. I recommend GNU `g++ 2.95` or newer.

The following C++ features are used: classes, member functions, overloading of functions and operators, constructors and destructors, inline, const, multiple inheritance, templates and namespaces.

The following C++ features are not used: `new`, `delete`, virtual inheritance, exceptions.

CLN relies on semi-automatic ordering of initializations of static and global variables, a feature which I could implement for GNU g++ only.

### 2.1.2 Make utility

To build CLN, you also need to have GNU `make` installed.

### 2.1.3 Sed utility

To build CLN on HP-UX, you also need to have GNU `sed` installed. This is because the libtool script, which creates the CLN library, relies on `sed`, and the vendor's `sed` utility on these systems is too limited.

## 2.2 Building the library

As with any autoconfiguring GNU software, installation is as easy as this:

    $ ./configure
    $ make
    $ make check

If on your system, ``make'` is not GNU `make`, you have to use ``gmake'` instead of ``make'` above.

The `configure` command checks out some features of your system and C++ compiler and builds the `Makefile`s. The `make` command builds the library. This step may take 4 hours on an average workstation. The `make check` runs some test to check that no important subroutine has been miscompiled.

The `configure` command accepts options. To get a summary of them, try

    $ ./configure --help

Some of the options are explained in detail in the ``INSTALL.generic'` file.

You can specify the C compiler, the C++ compiler and their options through the following environment variables when running `configure`:

`CC`
  Specifies the C compiler.
`CFLAGS`
  Flags to be given to the C compiler when compiling programs (not when linking).
`CXX`
  Specifies the C++ compiler.
`CXXFLAGS`
  Flags to be given to the C++ compiler when compiling programs (not when linking).

Examples:

    $ CC="gcc" CFLAGS="-O" CXX="g++" CXXFLAGS="-O" ./configure
    $ CC="gcc -V egcs-2.91.60" CFLAGS="-O -g" \
      CXX="g++ -V egcs-2.91.60" CXXFLAGS="-O -g" ./configure
    $ CC="gcc -V 2.95.2" CFLAGS="-O2 -fno-exceptions" \
      CXX="g++ -V 2.95.2" CFLAGS="-O2 -fno-exceptions" ./configure

Note that for these environment variables to take effect, you have to set them (assuming a Bourne-compatible shell) on the same line as the `configure` command. If you made the settings in earlier shell commands, you have to `export` the environment variables before calling `configure`. In a `csh` shell, you have to use the ``setenv'` command for setting each of the environment variables.

Currently CLN works only with the GNU `g++` compiler, and only in optimizing mode. So you should specify at least `-O` in the CXXFLAGS, or no CXXFLAGS at all. (If CXXFLAGS is not set, CLN will use `-O`.)

If you use `g++` version 2.8.x or egcs-2.91.x (a.k.a. egcs-1.1) or gcc-2.95.x, I recommend adding ``-fno-exceptions'` to the CXXFLAGS. This will likely generate better code.

If you use `g++` version egcs-2.91.x (egcs-1.1) or gcc-2.95.x on Sparc, add either ``-O'`, ``-O1'` or ``-O2 -fno-schedule-insns'` to the CXXFLAGS. With full ``-O2'`, `g++` miscompiles the division routines. Also, if you have `g++` version egcs-1.1.1 or older on Sparc, you must specify ``--disable-shared'` because `g++` would miscompile parts of the library.

By default, both a shared and a static library are built. You can build CLN as a static (or shared) library only, by calling `configure` with the option ``--disable-shared'` (or ``--disable-static'`). While shared libraries are usually more convenient to use, they may not work on all architectures. Try disabling them if you run into linker problems. Also, they are generally somewhat slower than static libraries so runtime-critical applications should be linked statically.

### 2.2.1 Using the GNU MP Library

Starting with version 1.1, CLN may be configured to make use of a preinstalled `gmp` library. Please make sure that you have at least `gmp` version 3.0 installed since earlier versions are unsupported and likely not to work. Enabling this feature by calling `configure` with the option ``--with-gmp'` is known to be quite a boost for CLN's performance.

If you have installed the `gmp` library and its header file in some place where your compiler cannot find it by default, you must help `configure` by setting `CPPFLAGS` and `LDFLAGS`. Here is an example:

    $ CC="gcc" CFLAGS="-O2" CXX="g++" CXXFLAGS="-O2 -fno-exceptions" \
      CPPFLAGS="-I/opt/gmp/include" LDFLAGS="-L/opt/gmp/lib" ./configure --with-gmp

## 2.3 Installing the library

As with any autoconfiguring GNU software, installation is as easy as this:

    $ make install

The ``make install'` command installs the library and the include files into public places (``/usr/local/lib/'` and ``/usr/local/include/'`, if you haven't specified a `--prefix` option to `configure`). This step may require superuser privileges.

If you have already built the library and wish to install it, but didn't specify `--prefix=...` at configure time, just re-run `configure`, giving it the same options as the first time, plus the `--prefix=...` option.

## 2.4 Cleaning up

You can remove system-dependent files generated by `make` through

    $ make clean

You can remove all files generated by `make`, thus reverting to a virgin distribution of CLN, through

    $ make distclean

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