libssh2/docs/INSTALL-AUTOTOOLS.md

# Installation Instructions

Copyright (C) 1994, 1995, 1996, 1999, 2000, 2001, 2002, 2004, 2005 Free
Software Foundation, Inc.

This file is free documentation; the Free Software Foundation gives unlimited
permission to copy, distribute and modify it.

SPDX-License-Identifier: FSFULLR

## When Building directly from Master

If you want to build directly from the git repository, you must first generate
the configure script and Makefile using autotools. Make sure that autoconf,
automake and libtool are installed on your system, then execute:

```sh
autoreconf -fi
```

After executing this script, you can build the project as usual:

```sh
./configure
make
```

## Basic Installation

These are generic installation instructions.

The `configure` shell script attempts to guess correct values for various
system-dependent variables used during compilation. It uses those values to
create a `Makefile` in each directory of the package. It may also create one
or more `.h` files containing system-dependent definitions. Finally, it
creates a shell script `config.status` that you can run in the future to
recreate the current configuration, and a file `config.log` containing
compiler output (useful mainly for debugging `configure`).

It can also use an optional file (typically called `config.cache` and enabled
with `--cache-file=config.cache` or shortly `-C`) that saves the results of
its tests to speed up reconfiguring. (Caching is disabled by default to
prevent problems with accidental use of stale cache files.)

If you need to do unusual things to compile the package, please try to figure
out how `configure` could check whether to do them, and mail diffs or
instructions to the address given in the `README` so they can be considered
for the next release. If you are using the cache, and at some point
`config.cache` contains results you do not want to keep, you may remove or
edit it.

The file `configure.ac` (or `configure.in`) is used to create `configure` by
a program called `autoconf`. You only need `configure.ac` if you want to change
it or regenerate `configure` using a newer version of `autoconf`.

The simplest way to compile this package is:

1. `cd` to the directory containing the package's source code and type
   `./configure` to configure the package for your system. If you are using
   `csh` on an old version of System V, you might need to type `sh ./configure`
   instead to prevent `csh` from trying to execute `configure` itself.

   Running `configure` takes awhile. While running, it prints some messages
   telling which features it is checking for.

2. Type `make` to compile the package.

3. Optionally, type `make check` to run any self-tests that come with
   the package.

4. Type `make install` to install the programs and any data files and
   documentation.

5. You can remove the program binaries and object files from the source code
   directory by typing `make clean`. To also remove the files that `configure`
   created (so you can compile the package for a different kind of computer),
   type `make distclean`. There is also a `make maintainer-clean` target, but
   that is intended mainly for the package's developers. If you use it, you may
   have to get all sorts of other programs in order to regenerate files that
   came with the distribution.

## Compilers and Options

Some systems require unusual options for compilation or linking that the
`configure` script does not know about. Run `./configure --help` for details
on some of the pertinent environment variables.

You can give `configure` initial values for configuration parameters by
setting variables in the command line or in the environment. Here is an
example:

```
./configure CC=c89 CFLAGS=-O2 LIBS=-lposix
```

   *Note Defining Variables::, for more details.

## Compiling For Multiple Architectures

You can compile the package for more than one kind of computer at the same
time, by placing the object files for each architecture in their own
directory. To do this, you must use a version of `make` that supports the
`VPATH` variable, such as GNU `make`. `cd` to the directory where you want the
object files and executables to go and run the `configure` script.
`configure` automatically checks for the source code in the directory that
`configure` is in and in `..`.

If you have to use a `make` that does not support the `VPATH` variable, you
have to compile the package for one architecture at a time in the source code
directory. After you have installed the package for one architecture, use
`make distclean` before reconfiguring for another architecture.

## Installation Names

By default, `make install` installs the package's commands under
`/usr/local/bin`, include files under `/usr/local/include`, etc. You can
specify an installation prefix other than `/usr/local` by giving `configure`
the option `--prefix=PREFIX`.

You can specify separate installation prefixes for architecture-specific files
and architecture-independent files. If you pass the option
`--exec-prefix=PREFIX` to `configure`, the package uses PREFIX as the prefix
for installing programs and libraries. Documentation and other data files
still use the regular prefix.

In addition, if you use an unusual directory layout you can give options like
`--bindir=DIR` to specify different values for particular kinds of files. Run
`configure --help` for a list of the directories you can set and what kinds of
files go in them.

If the package supports it, you can cause programs to be installed with an
extra prefix or suffix on their names by giving `configure` the option
`--program-prefix=PREFIX` or `--program-suffix=SUFFIX`.

## Optional Features

Some packages pay attention to `--enable-FEATURE` options to `configure`,
where FEATURE indicates an optional part of the package. They may also pay
attention to `--with-PACKAGE` options, where PACKAGE is something like
`gnu-as` or `x` (for the X Window System). The `README` should mention any
`--enable-` and `--with-` options that the package recognizes.

For packages that use the X Window System, `configure` can usually find the X
include and library files automatically, but if it does not, you can use the
`configure` options `--x-includes=DIR` and `--x-libraries=DIR` to specify
their locations.

## Specifying the System Type

There may be some features `configure` cannot figure out automatically, but
needs to determine by the type of machine the package runs on. Usually,
assuming the package is built to be run on the _same_ architectures,
`configure` can figure that out, but if it prints a message saying it cannot
guess the machine type, give it the `--build=TYPE` option. TYPE can either be
a short name for the system type, such as `sun4`, or a canonical name which
has the form:

```
CPU-COMPANY-SYSTEM
```

where SYSTEM can have one of these forms:

```
OS KERNEL-OS
```

See the file `config.sub` for the possible values of each field. If
`config.sub` is not included in this package, then this package does not need
to know the machine type.

If you are _building_ compiler tools for cross-compiling, you should use the
option `--target=TYPE` to select the type of system they produce code
for.

If you want to _use_ a cross compiler, that generates code for a platform
different from the build platform, you should specify the "host" platform
(i.e., that on which the generated programs eventually runs) with
`--host=TYPE`.

## Sharing Defaults

If you want to set default values for `configure` scripts to share, you can
create a site shell script called `config.site` that gives default values for
variables like `CC`, `cache_file`, and `prefix`. `configure` looks for
`PREFIX/share/config.site` if it exists, then `PREFIX/etc/config.site` if it
exists. Or, you can set the `CONFIG_SITE` environment variable to the location
of the site script. A warning: not all `configure` scripts look for a site
script.

## Defining Variables

Variables not defined in a site shell script can be set in the environment
passed to `configure`. However, some packages may run configure again during
the build, and the customized values of these variables may be lost. In order
to avoid this problem, you should set them in the `configure` command line,
using `VAR=value`. For example:

```sh
./configure CC=/usr/local2/bin/gcc
```

causes the specified `gcc` to be used as the C compiler (unless it is
overridden in the site shell script). Here is a another example:

```sh
/bin/bash ./configure CONFIG_SHELL=/bin/bash
```

Here the `CONFIG_SHELL=/bin/bash` operand causes subsequent
configuration-related scripts to be executed by `/bin/bash`.

## `configure` Invocation

`configure` recognizes the following options to control how it operates.

* `--help`, `-h`

  Print a summary of the options to `configure`, and exit.

* `--version`, `-V`

  Print the version of Autoconf used to generate the `configure` script, and
  exit.

* `--cache-file=FILE`

  Enable the cache: use and save the results of the tests in FILE,
  traditionally `config.cache`. FILE defaults to `/dev/null` to disable
  caching.

* `--config-cache`, `-C`

  Alias for `--cache-file=config.cache`.

* `--quiet`, `--silent`, `-q`

  Do not print messages saying which checks are being made. To suppress all
  normal output, redirect it to `/dev/null` (any error messages are still
  shown).

* `--srcdir=DIR`

  Look for the package's source code in directory DIR. Usually `configure`
  can determine that directory automatically.

`configure` also accepts some other, not widely useful, options. Run
`configure --help` for more details.

## More configure options

Some `./configure` options deserve additional comments:

* `--with-libgcrypt`
* `--without-libgcrypt`
* `--with-libgcrypt-prefix=DIR`

  libssh2 can use the [Libgcrypt](https://www.gnupg.org/) library for
  cryptographic operations. One of the cryptographic libraries is required.

  Configure attempts to locate Libgcrypt automatically.

  If your installation of Libgcrypt is in another location, specify it using
  `--with-libgcrypt-prefix`.

* `--with-openssl`
* `--without-openssl`
* `--with-libssl-prefix=[DIR]`

  libssh2 can use the [OpenSSL library](https://www.openssl-library.org/) for
  cryptographic operations. One of the cryptographic libraries is required.

  Configure attempts to locate OpenSSL in the default location.

  If your installation of OpenSSL is in another location, specify it using
  `--with-libssl-prefix`.

* `--with-mbedtls`
* `--without-mbedtls`
* `--with-libmbedcrypto-prefix=[DIR]`

  libssh2 can use the
  [mbedTLS library](https://www.trustedfirmware.org/projects/mbed-tls/) for
  cryptographic operations. One of the cryptographic libraries is required.

  Configure attempts to locate mbedTLS in the default location.

  If your installation of mbedTLS is in another location, specify it using
  `--with-libmbedcrypto-prefix`.

* `--with-libz`
* `--without-libz`
* `--with-libz-prefix=[DIR]`

  If present, libssh2 attempts to use the [zlib](https://zlib.net/) for
  payload compression, however zlib is not required.

  If your installation of Libz is in another location, specify it using
  `--with-libz-prefix`.

* `--enable-debug`

  Makes the build use more pedantic and strict compiler options as well
  as enable the `libssh2_trace()` function (for showing debug traces).