Brad King 0f150b69d3 AIX: Explicitly compute shared object exports for both XL and GNU
On AIX, symbols in shared objects must be exported in order to be
visible to dependents (similar to Windows).  The AIX linker provides a
`-bE:...` option to specify a file listing symbols to be exported.
Compilers offer some features to help:

* When the XL compiler is invoked with its `-qmkshrobj`/`-G` options for
  creating shared objects (without/with runtime linking), it recognizes
  when no explicit `-bE:...` linker option is specified and runs a
  `CreateExportList` tool provided with the compiler to compute one from
  the object files.  Since commit d468a2c2cb (XL: Avoid copying archives
  into shared libraries that link them, 2011-04-07, v2.8.5~153^2) CMake
  runs `CreateExportList` explicitly to ensure it only looks at the object
  files and not any library files.

* When the GNU compiler is invoked with its `-shared` option for creating
  shared objects, its internal `collect2` tool recognizes when no explicit
  `-bE:...` linker option is specified and computes one itself from the
  object files.  However, it sometimes includes extra symbols such as
  `.__init_aix_libgcc_cxa_atexit`.

Introduce our own internal `ExportImportList` script to compute symbol
export lists from object files.  Use a basic implementation for now: it
can be extended as needed later.  Update our shared library creation
rules to run the script explicitly for both the XL and GNU compilers.

Issue: #19163
2019-07-15 13:27:16 -04:00
2019-07-15 07:41:52 -04:00

CMake
*****

Introduction
============

CMake is a cross-platform, open-source build system generator.
For full documentation visit the `CMake Home Page`_ and the
`CMake Documentation Page`_. The `CMake Community Wiki`_ also
references useful guides and recipes.

.. _`CMake Home Page`: https://cmake.org
.. _`CMake Documentation Page`: https://cmake.org/cmake/help/documentation.html
.. _`CMake Community Wiki`: https://gitlab.kitware.com/cmake/community/wikis/home

CMake is maintained and supported by `Kitware`_ and developed in
collaboration with a productive community of contributors.

.. _`Kitware`: http://www.kitware.com/cmake

License
=======

CMake is distributed under the OSI-approved BSD 3-clause License.
See `Copyright.txt`_ for details.

.. _`Copyright.txt`: Copyright.txt

Building CMake
==============

Supported Platforms
-------------------

* Microsoft Windows
* Apple macOS
* Linux
* FreeBSD
* OpenBSD
* Solaris
* AIX

Other UNIX-like operating systems may work too out of the box, if not
it should not be a major problem to port CMake to this platform.
Subscribe and post to the `CMake Users List`_ to ask if others have
had experience with the platform.

.. _`CMake Users List`: https://cmake.org/mailman/listinfo/cmake

Building CMake from Scratch
---------------------------

UNIX/Mac OSX/MinGW/MSYS/Cygwin
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

You need to have a C++ compiler (supporting C++11) and a ``make`` installed.
Run the ``bootstrap`` script you find in the source directory of CMake.
You can use the ``--help`` option to see the supported options.
You may use the ``--prefix=<install_prefix>`` option to specify a custom
installation directory for CMake.  Once this has finished successfully,
run ``make`` and ``make install``.

For example, if you simply want to build and install CMake from source,
you can build directly in the source tree::

  $ ./bootstrap && make && sudo make install

Or, if you plan to develop CMake or otherwise run the test suite, create
a separate build tree::

  $ mkdir cmake-build && cd cmake-build
  $ ../cmake-source/bootstrap && make

Windows
^^^^^^^

There are two ways for building CMake under Windows:

1. Compile with MSVC from VS 2015 or later.
   You need to download and install a binary release of CMake.  You can get
   these releases from the `CMake Download Page`_.  Then proceed with the
   instructions below for `Building CMake with CMake`_.

2. Bootstrap with MinGW under MSYS2.
   Download and install `MSYS2`_.  Then install the required build tools::

     $ pacman -S --needed git base-devel mingw-w64-x86_64-gcc

   and bootstrap as above.

.. _`CMake Download Page`: https://cmake.org/cmake/resources/software.html
.. _`MSYS2`: https://www.msys2.org/

Building CMake with CMake
-------------------------

You can build CMake as any other project with a CMake-based build system:
run the installed CMake on the sources of this CMake with your preferred
options and generators. Then build it and install it.
For instructions how to do this, see documentation on `Running CMake`_.

.. _`Running CMake`: https://cmake.org/cmake/help/runningcmake.html

To build the documentation, install `Sphinx`_ and configure CMake with
``-DSPHINX_HTML=ON`` and/or ``-DSPHINX_MAN=ON`` to enable the "html" or
"man" builder.  Add ``-DSPHINX_EXECUTABLE=/path/to/sphinx-build`` if the
tool is not found automatically.

.. _`Sphinx`: http://sphinx-doc.org

Reporting Bugs
==============

If you have found a bug:

1. If you have a patch, please read the `CONTRIBUTING.rst`_ document.

2. Otherwise, please join the `CMake Users List`_ and ask about
   the expected and observed behaviors to determine if it is really
   a bug.

3. Finally, if the issue is not resolved by the above steps, open
   an entry in the `CMake Issue Tracker`_.

.. _`CMake Issue Tracker`: https://gitlab.kitware.com/cmake/cmake/issues

Contributing
============

See `CONTRIBUTING.rst`_ for instructions to contribute.

.. _`CONTRIBUTING.rst`: CONTRIBUTING.rst
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