[Tinyos-host-mote-wg] [Tinyos-2.0wg] packages for nesC: why/etc [shortish so you can glance through it this morning]

[David Gay]

Name space for tinyos components and interfaces is getting complex:

  - similar names needed for functionality at many layers:
    hpl, hal, hil, oski
  - similar names needed across platforms / chips
  - some components are "private": not intended for independent use
    (lookup, e.g., at tos/lib/FS in 1.x)

Prefixing is not a good solution: names become very awkward, prefixes are not
used consistently, etc.

------------

Proposal: add a package system to nesC

  packages contain component and interface files, and other packages
  issue: what about C names and include files? (see below)

  packages must be imported in a file before use
  packages can be imported with a "private" name
   (something like import "tinyos.lib.adc as foo", followed by uses
    like foo.SomeAdcInterface)
  some set of packages are automatically imported

--------------

Major issues:
- how to deal with C names?
- how to deal with C files, preprocessor macros?
i.e., are they part of the package system, which means that:
  - C file inclusion should either include the package name, or
    be searched for in imported packages
  - C names/preprocessor names would be searched for in imported
    packages (and support the importedasname.name syntax)

Reasons to include them:
- same as for components and interfaces: the packages will need to organise
  their type names, etc

Reasons not to include them:
- how does #include work within a package system?
  (short answer: it doesn't, we would need to go back to "includes foo;")
  (long answer on request)
- macroprocessing currently handled by external gcc invocation
  --> cannot handle macros in packages
      solution: integrate preprocessing into nesC compiler
                this allows "includes" and macros to work together...
- more changes from C, possible syntax issues

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