Platform Specific Projects

When a project involves platform-specific code, some consideration needs to be made to the LID file and registry, as well as the layout of code. As an example, consider the io and system libraries, found in https://github.com/dylan-lang/opendylan/tree/master/sources/io/ and https://github.com/dylan-lang/opendylan/tree/master/sources/system/.

LID File

For further details of the LID file format, see LID File Format.

  1. Library

    The library remains the same across all platforms since it is, after all, a platform-dependent version of that library:

    Keyword

    unix-io.lid

    win32-io.lid

    Library:

    io

    io

  2. Files

    Each platform’s project may contain files that are the same in each platform, as well as files which are present in one but not in another:

    Keyword

    unix-io.lid

    win32-io.lid

    Files:

    buffered-format

    buffered-format

    format-condition

    format-condition

    unix-interface

    win32-interface

    unix-file-accessor

    win32-file-accessor

    unix-standard-io

    win32-standard-io

    format-out

    format-out

    (etc)

    (etc)

    C-Source-Files:

    unix-portability.c

    RC-Files:

    version.rc

  3. Linked Libraries (from dylan-lang/opendylan/sources/system)

    Each platform’s project will probably require a different set of linked libraries:

    Keyword

    x86_64-linux-system.lid

    x86-win32-system.lid

    C-Libraries:

    -ldl

    advapi32.lib

    shell32.lib

    Note

    An example from the system library was used as the io library doesn’t link directly against any C libraries.

LID File Inheritance

When LID files are almost identical, it can be useful to create a base LID file and inherit it, overriding whatever is necessary for each platform. A per-platform LID file might look like:

Library:        uv
LID:            uv-posix.lid
C-libraries:    -framework CoreServices

Registry

For further details of setting up the registry entries, see Using Source Registries.

Normally, when a reference to a platform independent project is placed in the registry, it is put into the “generic” directory. Platform dependent projects are placed in subdirectories named for the platform. e.g.

opendylan/sources/registry/x86_64-linux/io

abstract://dylan/io/unix-io.lid

opendylan/sources/registry/x86-win32/io

abstract://dylan/io/win32-io.lid

Code Layout

The io library is laid out in the following manner:

  1. All platform-specific code is inside a single module (io-internals).

  2. *-interface.dylan contains the low-level functions accessing the platform-specific libraries (e.g. unix-read, win32-read).

  3. *-file-accessor.dylan uses the functions from (2) to produce a platform-independent API (e.g. accessor-read-into!).

  4. Only those methods from (3) are exported from the module.

Note

Most libraries that are portable aren’t as complex in their layout as the io library and don’t require separate modules.