Build Makefile [build]
======================

TODO


Build Work Area [work-area]
===========================

When building packages, a new directory named `tmp` shall be created in the
source package directory.  In this directory, the package source code shall be
copied or unpacked into a directory called `src` and an installation destination
directory named `dest` shall be created.

After all expected binary packages have been built, the work area (`tmp` and its
children) shall be removed.


Environment Variables [env-vars]
================================

Certain environment variables shall be set to provide to the configuration
script and build makefile information about the package and the environments in
and for which binary packages are to be built.

The terms "build system" and "host system" below are used according to [the
convention set by GNU Autoconf][target-triplets].  The build system is the type
of system on which a package is built.  The host system is the type of system on
which a binary package is expected to be natively installed and used.

Package Variables [env-vars-pkg]
--------------------------------

The following environment variables shall be set to describe the source package:

  * `OPK_SOURCE`

    The source package name, as given in the most recent entry of the change
    log.  See $[sectlink][changelog] for more information on the source package
    name.

  * `OPK_SOURCE_VERSION`

    The source package version, as given in the most recent entry of the change
    log.  See $[sectlink][src-ver] for the syntax of source package version
    identifiers.

  * `OPK_SOURCE_VERSION_UPSTREAM`

  * `OPK_BINARY_VERSION`

Build and Host System Variables [env-vars-sys]
----------------------------------------------

The following environment variables shall be set to describe the build system:

  * `OPK_BUILD_ARCH`

    The distribution architecture string of the build system.

  * `OPK_BUILD_ARCH_CPU`

    The CPU component of the distribution architecture string of the build
    system.

  * `OPK_BUILD_ARCH_KERNEL`

    The kernel component of the distribution architecture string of the build
    system.

  * `OPK_BUILD_ARCH_LIBS`

    The system libraries component of the distribution architecture string of
    the build system.

  * `OPK_BUILD_ARCH_GNU`

    The GNU system type of the build system.

  * `OPK_BUILD_PLAT`

    The application platform of the build system.

The following environment variables shall be set to describe the host system:

  * `OPK_HOST_ARCH`

    The distribution architecture string of the host system.

  * `OPK_HOST_ARCH_CPU`

    The CPU component of the distribution architecture string of the host
    system.

  * `OPK_HOST_ARCH_KERNEL`

    The kernel component of the distribution architecture string of the host
    system.

  * `OPK_HOST_ARCH_LIBS`

    The system libraries component of the distribution architecture string of
    the host system.

  * `OPK_HOST_ARCH_GNU`

    The GNU system type of the host system.

  * `OPK_HOST_PLAT`

    The application platform of the host system.

Toolchain Variables [env-vars-tools]
------------------------------------

The following environment variables shall be set to describe the toolchain:

  * `AR`

  * `AS`

  * `CC`

  * `CPP`

  * `CXX`

  * `LD`

  * `NM`

  * `OBJCOPY`

  * `OBJDUMP`

  * `RANLIB`

  * `READELF`

  * `SIZE`

  * `STRINGS`

  * `STRIP`

Note that the environment variables assume the use of GNU Binutils and GCC.
Support for other toolchains may be specified in a future version of this source
package format.


[target-triplets]: https://www.gnu.org/software/autoconf/manual/html_node/Specifying-Target-Triplets.html