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.

  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 win-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 the platform-labelled subdirectories. 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.